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Select this Article		Stochastic Assessment of Reservoir Storage‐Yield Relationships in Portugal: A Case Study A. T. Silva and M. M. Portela Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000650 Posted ahead of print 14 May 2012 Full Text: \| Download PDF
	+ -	Show Abstract This study aims to establish design criteria that simultaneously meet the stochastic nature of the streamflow regime in Portuguese rivers and the relationship between such regime and the mean annual flow depth, for the preliminary design of the storage capacity and yield of artificial reservoirs. The data set consisted of 54 streamflow samples from unregulated Portuguese rivers. To comply with the previously stated objectives a large number of monthly synthetic streamflow series was generated using, at the annual level, a probabilistic model based on the random sampling of the log‐Pearson III distribution and, at the monthly level, a disaggregation model, namely the method of fragments. Based on an operation with fixed values of yield and time‐based reliability, behavioral analysis was applied to the synthetic series to estimate the storage capacities of of hypothetical reservoirs. The Gumbel distribution was fitted to the previous estimates to obtain design storage capacities with specified values of reliability. After showing that the former design capacities were significantly correlated with the mean annual flow depth of the sample series, curves expressing that relationship were defined. The results consistently showed that, for a given operation condition, as the mean annual flow depth increases the required specific storage decreases. The curves expressing such relationship can be directly applied to the preliminary design of the storage capacity of reservoirs in Portuguese rivers. It is believed that similar curves can also be applied in Southern European countries with climatic characteristics similar to those of Portugal.

Select this Article		Preparation and Evaluation of a Dutch‐German Radar Composite to Enhance Precipitation Information in Border Areas Thomas Einfalt, Arnold Lobbrecht, KaYin Leung, and Guido Lempio Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000649 Posted ahead of print 14 May 2012 Full Text: \| Download PDF
	+ -	Show Abstract The Dutch weather radars in De Bilt and Den Helder have only limited coverage in the Dutch‐German border area in the north‐eastern part of the Netherlands, whereas the German radar in Emden is just across the border. For many years, local water authorities have been looking for a better quantitative precipitation estimate(QPE) for this region. Recently, a German water‐management consultancy: hydro & meteo and a Dutch one: HydroLogic have jointly taken up the challenge to develop a completely new precipitation radar composite for this part of the Netherlands. The new composite uses the basic polar radar products (volume data) of the two national weather bureaux. The composite should be able to meet precipitation‐information requirements of operational water managers; in other words it should be able to provide QPE in real time. The present case study of an interesting rainfall event demonstrates the capabilities of the new composite tool. The rainfall event was used to evaluate various filtering and correction algorithms. QPE results were verified against independent rain‐gauge data. On average, the results of the new composite were found to be similar to the Dutch weather bureau's QPE for the entire Netherlands. However, the new composite yielded a much better QPE for the north‐eastern part of the country, as a result of the addition of the Emden radar data. The algorithms we developed are ready to be applied in operational water‐management by water boards and municipalities in the north‐eastern part of the Netherlands.

Select this Article		GIS‐Based Numerical Modeling of Aquifer Recharge and Salt Water Intrusion in Arid South Eastern Tunisia N. Gaaloul Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000648 Posted ahead of print 14 May 2012 Full Text: \| Download PDF
	+ -	Show Abstract Water resources globally face unprecedented challenges, but these are at their greatest in the world's arid and semi‐arid regions. Groundwater plays an important role in the economic development and ecological balance of the arid area of south east Tunisia. This paper presents the potential to use saline water in sustainable agricultural production in arid south east of Tunisia and the development of a numerical model of groundwater flows for the aquifer system of El Hicha aquifer. It presents the quantity and quality of saline water resources data and the integration of poverty indicator information with saline water resources. The numerical model constitutes the main method used to solve the groundwater quantity management problems and to evaluate the groundwater flow mixing between different aquifer levels. A groundwater numerical model for El Hicha Basin, an arid area of south east Tunisia, was developed using MODFLOW software to simulate regional groundwater changes under steady state and transient conditions. The results from calibration of the model show reasonable agreement between observed and calculated water for the observation wells. The reliability of the model is tested by a long series of historical groundwater monitoring data and the model is then used to predict the impact of groundwater exploitation until 2020 and 2050. It is shown a significant drawdown and an enhanced seawater intrusion in the El Hicha aquifer. Under current water resources management conditions, groundwater levels in the El Hicha aquifer are in a continuous drawdown trend. It is necessary to take measures to reduce groundwater exploitation to protect the ecological environment.

Select this Article		Hydraulic Lift Empirical Test among Native Plant Species in the Horqin Sandy Land, Northern China Ala MuSa, Qin Zong, and Cunyang Niu Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000644 Posted ahead of print 2 May 2012 Full Text: \| Download PDF
	+ -	Show Abstract Hydraulic lift is the process by which some deep‐rooting plants take in water from deep soil layers and exude that water into the upper, drier soil layers through the root system. It is favorable for plants that transport the water, and at the same time, may be an important water source for neighboring plants. Hydraulic lift increases the stability of plantation communities and improves the growth of plants on semiarid sandy soil. The objectives of the present study were to examine the hydraulic lift ability of sandy plants and define the characteristic of this process in the Horqin Sandy Land. We used growth boxes to cultivate examined plants, isolating the upper and the lower layers with Vaseline. We controlled the soil water supply of topsoil in growth boxes during the examination period, and confirmed the hydraulic lift by measuring the variations in soil water content in the topsoil in the growth boxes. Hydraulic lift was investigated in 21 native plants in the Horqin Sandy Land, and all of these plants are deep rooting. The hydraulic lift process may be common to deep‐rooting psammophytes, and it mostly occurs from 24:00 to 06:00. The quantity of hydraulic lift water among the 19 species varied. The increment of soil water content lifted by each gram of root biomass within 24 h were between 4.86–325.62 g⋅g⁻¹, with an average of 72.90 g⋅g⁻¹. The species Artemisia wudanica, Artemisia gmelinii, Thermopsis lanceolata, and Bassia dasyphylla have the strongest hydraulic lift abilities among all examined species. No distinctive correlation was observed between the degree of drought in the topsoil and the total water lifted by the process. We can use the hydraulic lift of psammophytes to improve the water content of shallow soil, which may have important significance in vegetation establishment on semiarid sandy land.

Select this Article		Root Water Uptake Model Considering Soil Temperature Guohua Lv, Wei Hu, Yaohu Kang, Buchun Liu, Lan Li, and Jiqing Song Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000642 Posted ahead of print 30 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Field experiment was carried out to research the effect of soil temperature distribution on root water uptake in soil water simulation. Soil temperature distribution patterns under border irrigation and surface drip irrigation were researched. Root water uptake model was modified based on the effect of soil temperature on root water uptake. Results showed soil temperature profile distribution was greatly influenced by irrigation method. Range of temperature was larger under border irrigation, with temperature being 3–6°C higher in 0–20 cm depth than in 20–100 cm depth. Except for the top layer under surface drip irrigation, mean soil temperature showed the trend of exponential decay throughout the soil profile. The relationship between temperature and water uptake rate was expressed in exponential function according to the previous research. With the modification of root water uptake model as affected by temperature profile distribution, the value of root mean square error between the simulated and observed soil water decreased from about 0.04 to 0.02 in the top layer under border irrigation, but showed no obvious difference under surface drip irrigation. When soil temperature differed greatly in the top layer from the deep layer, root water uptake model considering soil temperature could improve the precision of soil water simulation. The results indicated that the modified root water uptake model could be used to simulate soil water dynamics.

Select this Article		Rainfall Interception in a Robinia Pseudoacacia Forest Stand: Estimates Using Gash's Analytical Model Li Wang, Qingfeng Zhang, Ming'an Shao, and Quanjiu Wang Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000640 Posted ahead of print 28 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract We have studied the principal components of rainfall interception loss in a planted forest stand of Robinia pseudoacacia on the Loess Plateau. Our purpose was to provide new information about the applicability of the original Gash analytical model to a new geographic location and to one of the main species being used in the region's reforestation program. We estimated forest structure parameters, including the mean evaporation rate ( Ē ), the canopy storage capacity at saturation ( S ), the free throughfall coefficient ( p), the rainfall fraction diverted to the trunks ( p_t ), and the trunk storage capacity ( S_t ) by using the intercepts and slopes obtained from regression analyses of the measured interception loss, throughfall, and stemflow versus gross rainfall. The interception and components of interception loss for trees in a Robinia pseudoacacia forest located on a south‐facing slope were calculated using Gash's analytical model. The total estimated interception loss during the period of observation was 10.8 % higher than that calculated on the basis of measurements of the gross rainfall, throughfall, and stemflow. The good agreement between the estimated and measured values indicates that Gash's analytical model is suitable for estimating interception loss in forests on the Loess Plateau of China.

Select this Article		Independent Assessment of Incremental Complexity in the NWS Multi‐Sensor Precipitation Estimator Algorithms Emad Habib, Lingling Qin, Dong‐Jun Seo, Grzegorz J. Ciach, and Brian R. Nelson Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000638 Posted ahead of print 26 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract 1. This paper presents a comprehensive inter‐comparison analysis of different radar‐based multi‐sensor precipitation products generated operationally by the National Weather Service (NWS) Multi‐sensor Precipitation Estimator (MPE) algorithm from the WSR‐88D and concurrent rain gauge data. The analysis provides close insight into different effects of the increasing degree of complexity in the MPE algorithms. First, a gauge‐only product produced by the MPE algorithm was assessed. Then six MPE products were analyzed: a radar‐only product, a mean‐field bias adjusted product, a local bias‐adjusted product, two products that are based on merging the bias‐adjusted products with gauge observations, and a final product that includes human intervention by NWS forecasters. Data from a dense, carefully maintained experimental rain gauge cluster are used as an independent surface reference. A number of summary and conditional statistics are applied to the product inter‐comparisons. The results reported in this paper show that the most effective improvement of the rainfall products comes from applying the mean‐field bias adjustment to the radar‐only product. The analysis demonstrates that, for the current study site, some best‐intended schemes for optimal merging of radar and rain gauge data processing did not necessarily lead to clear improvements and, in some respects, caused accuracy degradation in the final products. This behavior by the MPE merging schemes is possibly attributed to the rather poor density of operational rain gauges that need to be available in real‐time for the implementation of such schemes. Future research is required to examine whether this behavior persists in other regions that may have better coverage and availability of operational rain gauges.

Select this Article		Spatial Assessment of Five Years of WSR‐88D Data over the Mississippi River Basin and Its Estimation Bias around Rain Gage Sites Michael J. Rogalus, III, P.H. and Fred L. Ogden, Ph.D., P.E., P.H., M. ASCE Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000636 Posted ahead of print 25 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Statistical analyses were performed using five years (1996–2000) of WSR‐88D weather‐radar rainfall estimates that were produced for the Global‐Continental scale International Project (GCIP) over the entire Mississippi River basin. The GCIP radar rainfall estimates were adjusted using a Z‐R relation optimized to improve performance at the time scale of individual storms. The accuracy of radar‐rainfall estimates were analyzed during the warm season considering a number of factors including: number of overlapping radars, distance from gage to nearest radar, gage elevation, and the geographic location of the radar. Results were used to identify Optimal Radar‐Rainfall Estimation Areas (ORREAs) within the Mississippi River basin with high correlation between storm‐total radar and rain gage rainfall. Additionally, estimation of the bias between storm‐total radar‐rainfall and rain gage rainfall accumulations in areas without gages was assessed to identify appropriateness of applying bias adjustments derived from gage data at points away from those rain gages.

Select this Article		Simulation of a Multi‐Layer Leaky Aquifer with Stream Depletion Nicholas Dudley Ward and Samuel Falle Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000634 Posted ahead of print 25 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Semi‐analytic formulae are obtained for flow to a well screened in a leaky aquifer overlain by an aquitard and phreatic aquifer, and underlain by a second aquitard and leaky aquifer. Formulae are also obtained for the case in which the phreatic aquifer is hydraulically connected to a rectilinear stream. Adaptive mesh refinement is used to obtain highly resolved simulations for a meandering stream depletion problem which is both numerically challenging and has physically interesting features. We also consider the associated inverse problem and give a simple example of synthetic pumping test data which shows that it can be very difficult to quantify the actual effects of pumping. We conclude that a framework for uncertainty quantification of aquifer parameters is necessary for their objective determination.

Select this Article		Runoff and Soil Loss from Revegetated Grasslands in Hilly Loess Plateau Region, China: Influence of Biocrust Patches and Plant Canopies Yunge Zhao and Mingxiang Xu Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000633 Posted ahead of print 16 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Biological soil crusts (biocrusts) cover up to 60–70% of soil surface in grasslands rehabilitated since the “Grain for Green” project was implemented in the hilly Loess Plateau region in 1999, which exerted significant impacts on runoff and soil loss from revegetated grasslands. In the study, field plots were used to investigate runoff and soil loss in sites of a 4‐year and a 13‐year revegetated grassland with each exhibiting an early and a later successional biocrusts, respectively. The objectives of the study were to: 1) examine the role of biocrusts played on runoff and soil loss during their early and later successional stages in semi‐arid region under water erosion; 2) determine the influence of biocrusts on soil anti‐scourability under different runoff intensities; and 3) isolate the effects of biocrust patches and vascular plants canopies on runoff and soil loss from revegetated grasslands. Treatments used in both sites included: a) retaining biocrusts and plant canopies intact (CP); b) retaining biocrusts without plant canopies (CNP); c) retaining plant canopies without biocrust (PNC); and d) removing both biocrusts and plant canopies (NCP). The simulated scouring water flux was designed as 7.8 l###min⁻¹, 12.0 l###min⁻¹ and 16.0 l###min⁻¹ to reflect local rainfall conditions. The results indicated that the runoff yield was increased by biocrusts patches in their well development stage. Runoff was increased by 15.1% when plant canopies were retained and 16.0% when plant canopies were removed in the 13‐year revegetated grassland under the 12.0 l###min⁻¹ scouring water flux. Compared to biocrust patches, plant canopies reduced runoff by 11.3% (with biocrusts) and 8.4% (biocrusts was removed) under the same scouring water flux. No significant difference was found in runoff yield under the four treatments in the 4‐year revegetated grassland. While 92% sediments was reduced for the formation of biocrusts in their early successional stage (cyanobacteria‐dominated) in the 4‐year revegetated grassland under CNP compared with NCP at the 12.0 l/min scouring intensity. No sediment was generated on either CP or CNP treatments in grassland revegetated for 13 years (moss‐dominated biocrusts) under the same intensity of simulated runoff. Compared to biocrusts, plant canopies had a limited influence on soil loss. This amounted to reductions of 45% and 10% in soil loss for grasslands that revegetated for four years and 13 years, respectively. The results of the study suggested that biocrusts play an important role in soil loss controlling from water erosion in semi‐arid regions, although there was a potential increased in runoff yield.

Select this Article		Assessing the Impacts of Future Climate Change on Hydrology in Huang‐Huai‐Hai Region in China Based on PRECIS and VIC Model Gui‐Hua Lu, Heng Xiao, Zhi‐Yong Wu, Si‐Long Zhang, and Yan Li Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000632 Posted ahead of print 14 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract The climate change impact on hydrology in China's Huang‐Huai‐Hai (H‐H‐H) region was assessed in this study. Both variations in mean monthly and annual runoff and occurrences of extreme events including flood and drought were examined for two future periods (2001–2030; 2016–2045) in the whole region. The projected daily maximum and minimum temperature and precipitation from the PRECIS (Providing Regional Climates for Impacts Studies) regional climate model were used to drive the VIC (Variable Infiltration Capacity) hydrology model. VIC was run over a regional domain of total 408 grid points at a spatial resolution of 50 km × 50 km. The result shows that PRECIS projects increases in both future temperature (0.8–1.5°C) and precipitation (3.5–7.3%) in the H‐H‐H region under the fourth IPCC (Intergovernmental Panel on Climate Change) SRES (Special Report on Emissions Scenarios) A2 and B2 scenarios. Over the entire H‐H‐H region, VIC projects increases of 11.3% and 13.7% in mean annual runoff by the 2015s (2001–2030) and 2030s (2016–2045) under the A2 scenario, respectively. Such increases would be 5.6% and 5.9% under the B2 scenario. The spatial temporal variation of mean annual runoff is likely uneven. For example, the mean annual runoff could decrease by 10% in the south of the Haihe River basin by the 2015s under the B2 scenario. However, an increase of 10% is likely to occur in the northeast part of the same basin. While for the mean monthly runoff, the increase would be significant from July through October and the runoff could exhibit a great inter‐annual variability. Extreme events such as droughts and severe floods could become more frequent in certain areas of the H‐H‐H region. The occurrence of drought events is likely to increase in summer and autumn seasons in most areas of the H‐H‐H region. Severe floods might also frequently occur in the Huaihe River basin.

Select this Article		Risk Zone Prediction in Meandering Rivers by Using a Multivariate Approach Alfonso Gutierrez‐Lopez, Vladimir Contreras, Aldo I. Ramirez, and Roberto Mejía‐Zermeño Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000631 Posted ahead of print 13 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract The formulation of Kinoshita curves takes into account a number of physiographic characteristics as well as the configuration of the river; however, it is the curve amplitude, the one that represents the main characteristic of this formulation. This main feature is known as the angular sinuosity coefficient (θ). In this paper this formulation is used as a base equation to improve an alternative expression for meander prediction, based on a stochastic multivariate analysis of the geomorphologic and physiographic characteristics of a river. By using this formulation as a time series, the method has been validated with stochastic models. The prioritization of the variables obtained through an empirical orthogonal functions (EOF) analysis clearly showed the existence of three groups of parameters, which altogether explain the behavior of the meandering of Cahuacan River. The first group is form by the morphologic characteristics of the river. The second group corresponds to the hydrologic features of the basin and the third one to the morphologic and geometric characteristics of the river. The computation of the confidence limits of this new methodology, although from a stochastic approach constitutes an alternative to consolidate the arguments that define the hypothetic zones at potential risk and make a validation of these directly in filed.

Select this Article		Effects of Measurement Method, Scale, and Landscape Features on Variability of Saturated Hydraulic Conductivity Wei Hu, Mingan Shao, Quanjiu Wang, and Dongli She Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000630 Posted ahead of print 29 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Knowledge of soil saturated hydraulic conductivity (Ks) and its spatial variation is important to characterize hydrological processes. The objective was to quantify three important variability components, i.e., measurement technique, spatial arrangement in sampling, and differing landscape features (sloped surfaces and gullies), in order to map Ks distribution in eroded watersheds like the Chinese Loess Plateau. Classic‐and geo‐statistics were employed to explore the effects of measurement method, sampling scale, and landscape position on the Ks and its spatial variation. In a small watershed with an area of 0.2‐km², three techniques including soil core method (SC), tension infiltration method (TI), and Guelph permeameter method (GP) were employed to determine surface Ks at 124 positions on the sloped landscape (minimum sampling space of about 10‐m). Furthermore, SC method was applied at 204 positions along four 100‐m transects (minimum sampling space of 2‐m), and 200 positions along four 10‐m transects (minimum sampling space of 0.2‐m) on the sloped landscape and 45 positions in the gully areas to determine surface Ks. The results showed that no significant differences of mean logarithmic value of Ks (Log₁₀Ks) existed for SC and GP, and the spatial patterns behaved the same for TI and GP. The spatial dependence decreased with a decrease in sampling extent. Structured variability was not observed at the 10‐m transect scale. When the minimum sampling space changed from 10 to 2‐m, the nugget variance decreased, the structured variance, sill variance, and spatial dependence increased. When minimum sampling space changed from 2 to 0.2‐m, the changes in spatial pattern of Ks were negligible, implying that a minimum sampling space of 2‐m is needed to capture the spatial pattern of Ks. Ks in the gully areas was significantly less than on the sloped positions. The spatial pattern of Ks changed when the gully positions were included. Gully areas, therefore, should be considered for characterizing the spatial pattern of Ks for watersheds in the Chinese Loess Plateau.

Select this Article		Modeling the Effects of Climate Change and Human Activities on the Hydrological Processes in a Semi‐Arid Watershed of Loess Plateau Qing Yun Li, Xin Xiao Yu, and Zhong Bao Xin Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000629 Posted ahead of print 27 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract The hydrological cycle in a catchment is sensitive to climate and land‐use changes. We conduct a case study to validate the performance of the Soil and Water Assessment Tool (SWAT) and its applicability as a simulator of runoff and sediment transport processes at the mesoscale scale in arid and semi‐arid areas. SWAT is used to simulate runoff and sediment changes caused by human activities in a typical watershed, the Jihe Watershed (1019 km²), in the Loess Plateau of Northwestern China. A marked increase in temperature was observed over the analysis period. The investigation is conducted using 47‐year historical rainfall/runoff data and sedimentary records from 1962 to 2008. The data from 1962 to 1981 was used for calibration and that from 1982 to 2008 for validation. Results showed that the Nash‐Sutcliffe model efficiency coefficient was about 0.7, the relative error was below 15%, and the coefficient of determination was more than 0.7 both for annual flow and sediment yield in the calibration period. These findings indicated that the SWAT model was able to simulate runoff and sediment yield satisfactorily; however, it exhibited better performance for the calibration period than it did for the validation period. Similarly, simulations of monthly flow and sediment were better for the calibration period. The simulated and observed values agree well with trend changes. Uncertainty analysis indicates that digital elevation model resolutions and watershed subdivisions imposed little influence on annual flow, but notable effects on annual sediment yield.

Select this Article		Effects of Mono‐Vegetation Restoration Types on Soil Water Distribution and Balance on a Hillslope in Northern Loess Plateau of China Xiaoli Fu, Mingan Shao, Xiaorong Wei, Huimin Wang, and Chen Zeng Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000628 Posted ahead of print 27 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract In the Loess Plateau of China, mosaic‐vegetation restoration by converting cropland into fallow (to regenerate natural vegetations) and perennials performs well in soil erosion control. However, soil desiccation caused by the planted perennials threatens the sustainability of vegetation restoration. Understanding of soil water distribution and balance in mono‐vegetation systems at hillslope scale is crucial for building a constructive mosaic‐vegetation restoration pattern in Northern Loess Plateau. Our objectives in this study were to investigate effects of mono‐vegetation restoration types on soil water distribution and balance and discuss the possible implications of the mono‐vegetation hydrological properties for mosaic‐vegetation pattern establishment at hillslope scale. In 2004, we chose a one‐piece waste hillslope with uniform slope of 12 degrees and established four mono‐vegetation plots subjected to shrub, grass, fallow and cropland. Shrub, grass and fallow are the typical vegetation restoration types, while cropland presents the traditional land use. Soil water content profiles, down to 400 or 600 cm depth, along the hillslope were measured with a neutron moisture meter from May to October in 2004, 2008, and 2009. Results showed that the rainfall infiltration depth was approximately 100 cm for shrub and grass, but exceeded 300 cm for fallow and cropland. Six growth years later, shrub, grass, and fallow depleted more soil water than cropland, in the amount of 288, 313, and 62 mm, respectively. Soil water depletion in shrub and grass resulted in dried soil layers at the depth of 100 – 260 cm and 100 – 360 cm. Water balance results indicated that soil water deficit occurred in June during the rain season. We observed that downhill‐accumulation of soil water storage, down to 400 cm depth, existed for fallow and cropland in 2004 and 2009. However, 6 growth years of shrub and grass substantially weakened such soil water downhill‐accumulation tendency. This fact alone suggests that a mosaic vegetation system of planting shrub/grass on downhill and setting fallow on uphill would be appropriate from a standpoint of maintaining the sustainable development of vegetation restoration in the study area. Further experiments should be performed to develop the mosaic‐vegetation patterns meeting the interests of both erosion control and sustainability of vegetation restoration.

Select this Article		Ground Water Flow Modelling of an Hard Rock Aquifer ‐ a Case Study V. Varalakshmi, B. Venkateswara Rao, L. SuriNaidu, and M. Tejaswini Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000627 Posted ahead of print 27 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract The present study area is mainly underlain by granites, basalts and a little part of laterites. Ground water occurs under unconfined to semi‐confined conditions in weathered and fractured formations respectively. A three dimensional ground water flow model for the Osmansagar and Himayathsagar catchments ‐ a semi‐arid hard rock area in India with two conceptual layers is developed under transient conditions using visual MODFLOW software for the period 2005 to 2009. The top layer is considered as 15 to 20 m weathered zone followed by second layer with 20–25 m fractured zone based on hydrogeophysical studies and borehole lithologs. The groundwater recharge estimation is achieved with the help of GIS and water table fluctuation method that is well fitted into the flow model with an average recharge value of 21% of the average annual rainfall. The results derived from modeling indicate that the average input to the aquifer system is 321.96 Million Cubic Metre (MCM) and the output is 322.14 MCM. It is also found that if the same withdrawal is continued up to the year 2020 the, water level declines more than 45 m over the entire study area. To avoid this critical stage, the present draft should be decreased by nearly 40%.

Select this Article		Rainfall Intensity‐Duration‐Frequency Relationships for Andhra Pradesh, India: Changing Rainfall Patterns and Implications for Runoff and Groundwater Recharge Daniel Dourte, Sanjay Shukla, Piara Singh, and Dorota Haman Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000625 Posted ahead of print 27 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Accurate and current rainfall characterization is an important tool for water‐related system design and management. Updated rainfall intensity‐duration‐frequency (IDF) relationships in peninsular India were developed; impacts on runoff and groundwater recharge due to changes in rainfall characteristics are discussed. Two datasets were used from gauges in Hyderabad city, the capital of Andhra Pradesh: hourly rainfall data for the 19 years from 1993–2011 and daily rainfall data for the 30 years from 1982–2011. Hourly data were used to develop updated rainfall IDF relationships; daily data were used for trend analysis of threshold‐based rainfall events. IDF curves were developed for return periods of 2, 5, 10, 15, 25, 50, 75, and 100 years for 1, 2, 4, 8, and 24 hour durations. The updated IDF relationships showed a significant change in rainfall characteristics compared to older relationships for the region surrounding Hyderabad, India; they showed greater rainfall intensities across all durations and return periods. Greater intensity storms may reduce groundwater recharge and increase runoff, making the surface storage of runoff increasingly important to enhance recharge and reduce flooding risks.

Select this Article		Three Dimensional Groundwater Contamination Source Identification Using Adaptive Simulated Annealing Manish Jha and Bithin Datta Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000624 Posted ahead of print 26 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Determination of groundwater contaminant source characteristics such as release histories of unknown groundwater pollutant sources from concentration observation data is an inverse problem. Since the solution of this problem is highly sensitive to measurement errors either in the observation data or model parameters, it can have non‐unique solutions and is therefore classified as an ill‐posed problem. Several methods have been suggested in literature to solve this problem. One of the most efficient of these methods is the linked simulation‐optimization based approach. However, this approach is computationally intensive and the results obtained tend to be highly susceptible to errors in the measured data and estimated hydro geological parameters. Apart from this, accuracy of the solutions is highly dependent on the choice of monitoring locations. An Adaptive Simulated Annealing (ASA) based solution algorithm is shown to be computationally efficient for optimal identification of the source characteristics in terms of execution time and accuracy. This computational efficiency appears to prevail even with moderate levels of errors in estimated parameters and concentration measurement errors. Also, the contaminant concentration monitoring locations are shown to be critical in the efficient characterization of the unknown contaminant sources. Optimal identification results for different monitoring networks are presented to demonstrate the relevance of a suitable network to efficient source identification.

Select this Article		Low Flow Variations in Source Water Supply for the Occoquan Reservoir System Based on a 100‐Year Climate Forecast Philip P. Maldonado, P.E., M. ASCE and Glenn E. Moglen, Ph.D., A. M. ASCE Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000623 Posted ahead of print 26 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract The onset of climate and land use change is forcing water managers to develop new techniques in response to the changing environment. This study uses established techniques to incorporate both projected climate change and projected land use change into a hydrologic model of the Occoquan watershed, which encompasses an area of approximately 1,550 square kilometers in Northern Virginia, U.S.A. The techniques used develop a future projection of weather that re‐creates the historic time series, including the drought of record, as influenced by climate change, thereby facilitating integration into existing water management practices. Incorporating land use and using multiple low‐flow (drought) analysis metrics allow for the determination of variations between the historic and future model flows. This study revealed a likelihood of increased low flow volumes for the Occoquan watershed from both climate and land use change, of which the majority were produced from land use change in combination with expanded reclaimed water supply. Also, the increases from climate change, while influencing measurable changes in flow patterns were much less than those from land use change.

Select this Article		Modeling Soil Solute Release into Runoff and Transport with Runoff on a Loess Slope Wencai Dong and Quanjiu Wang Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000622 Posted ahead of print 26 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Rainfall results in the transfer of chemicals from soil into surface runoff. We have developed a physically‐based solute transport model for estimating the solute concentration in runoff originating from the soil surface. Our model accounts for the effects of soil infiltration, raindrops, the water runoff rate, and the return flow, all of which influence the concentration of the solutes in the runoff. We assumed that the depth of mixing zone changed with the varieties of the raindrop hits, return flow and overland flow. We also assumed that runoff and soil in the mixing zone mixed instantaneously and that the solute in the soil beneath the mixing zone was moved to the mixing zone by diffusion. The mixing zone was included in our model and was based on the ‘deposited layer’. or ‘shield’. concept. To test our model, we carried out laboratory experiments that used two soil types and exposed them to simulated rainfall. The results simulated by the model were highly correlated with the experimental data. In the first few minutes after rainfall began, the solute concentration in the runoff was mainly controlled by the rainfall rate and solute concentration in the mixing zone; higher solute levels in the mixing zone resulted in higher solute concentrations in runoff. When the solute concentration in the runoff stabilized, the solute concentration in the runoff was mainly controlled by the diffusion of solutes from the soil beneath the mixing zone. The simulated data showed a high level of correlation with the measured data for both runoff volume and solute concentration in the runoff. This demonstrates that the model captured the temporal behavior of the runoff and solute transport in the runoff.

Select this Article		Entropy‐Based Method for Bivariate Drought Analysis Z. Hao and V. P. Singh Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000621 Posted ahead of print 26 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Drought duration and severity are two main properties for characterizing droughts. These drought properties are mutually correlated and may have different marginal distributions. A bivariate (or joint) distribution of drought duration and severity is therefore needed that is capable of accommodating their different marginal distributions. This study proposes a method, based on entropy theory, for constructing the bivariate distribution of drought duration and severity with different marginal distribution forms. By specifying constraints for drought duration and severity, the entropy‐based bivariate distribution can be derived and then marginal distributions can be obtained accordingly. Monthly streamflow data from Brazos River at Waco, Texas, are employed to illustrate the application of the proposed method to model drought duration and severity for drought analysis. The copula method is also applied for comparison with the proposed entropy method.

Select this Article		Assessment of Right‐Tail Prediction Ability of Some Distributions by Monte‐Carlo Analyses Tefaruk Haktanir, Murat Cobaner, and Beyza Gorkemli Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000620 Posted ahead of print 26 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract The probability distributions of Gumbel, 3‐parameter log‐normal (LN3), general extreme values (GEV), 3‐parameter gamma (G3), and 3‐parameter log‐gamma (LG3), whose parameters are computed by the methods of moments (MOM), maximum‐likelihood (ML), probability‐weighted moments (PWM), and self‐determined probability‐weighted moments (SDPWM) are compared from the aspect of predicting the right‐tail quantiles of return periods in the range: 10 ≤ T ≤ 10,000 years from finite‐length sample series by a Monte Carlo analysis. The parameters of the LN3 distribution are also computed by the method of ‘zero‐sample‐skewness’. Synthetic series of 1Million elements having skewness coefficients: +0.5, +1, +2, +3, +5 are generated by LN3, GEV, and G3 distributions, separately, resulting in 15 different 1Million‐element synthetic series (= 5 skewnesses × 3 distributions). The right‐tail quantiles having exceedence probabilities (Pex): 0.1, 0.05, 0.02, 0.01, 0.005, 0.002, 0.001, 0.0005, 0.0002, 0.0001 are first computed by the parent distribution. The right‐tail quantiles having those Pex's are also computed by these 21 probability models using all 1Million/n short series of lengths: n = 20, 30, 50, 100, 200. Instead of biases and root‐mean‐square‐errors of 1Million/n differences of quantiles from those of the parent distribution separately for individual return periods (T), like 100 years, 1000 years, etc., which has been the usual procedure so far, mean relative differences (MRD_j's), mean absolute relative differences (MARD_j's), standard deviations of relative differences (SDRD_j's), and standard deviations of absolute relative differences (SDARD_j's) of the areas between the frequency curves of the short series and the frequency curve of the parent distribution over the entire range: 0.0001 ≤ Pex ≤ 0.1 are proposed. Ranked tables of MRD_j's, MARD_j's, SDRD_j's, and SDRD_j's computed from 1Million/n n‐element series are investigated as a more comprehensive criterion of goodness of a probability distribution to predict right‐tail population quantiles from short‐length sample series. The G3‐PWM distribution is found to be better, followed by the LN3‐MOM, LN3‐PWM, G3‐MOM, GEV‐MOM, and LN3‐ML distributions for the ranges covered.

Select this Article		Assessing NEXRAD P3 Data Effects on Stream‐Flow Simulation Using SWAT Model in an Agricultural Watershed R. K. Gali, K. R. Douglas‐Mankin, X. Li, and T. Xu Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000618 Posted ahead of print 26 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Radar‐derived NEXRAD Process 3 (P3) data offer high spatial resolution precipitation data that might improve stream‐flow simulation accuracy using watershed models. The objective of this study was to assess the performance of spatially averaged subwatershed‐specific P3 data on stream‐flow simulations using the Soil and Water Assessment Tool (SWAT) hydrologic model. This study was the first to evaluate the P3 product in watershed modeling. The SWAT model was chosen to simulate hydrological processes in North Fork Ninnescah Watershed (2400 km²) located in south‐central Kansas. A precipitation gauge (PG) station was created for each subwatershed using an area‐weighted average of P3 precipitation estimates for all 16‐km² grid cells intersecting the subwatershed. Average subwatershed area (19 km²) was selected to correspond roughly with NEXRAD cell area to minimize spatial aggregation of radar precipitation data. The SWAT model was calibrated with both P3 data and PG data from 1 January 2002 to 31 December 2008. The P3‐calibrated model was validated using both different precipitation source data for the same simulation period (2002–2008) and the same source data with an independent simulation period (1996–2001). The PG‐calibrated model yielded slightly higher Nash‐Sutcliffe efficiency (E_NS), both daily (0.40) and monthly (0.60), than the P3‐calibrated model (daily: 0.35, monthly: 0.52); percent bias was very good (<± 2%) for both P3‐ and PG‐calibrated models at all time scales. Validation E_NS results, however, were diminished using PG data with the P3‐calibrated model (daily: 0.27, monthly: 0.52) but remained similar using P3 data with the PG‐calibrated model (daily: 0.40, monthly: 0.52). The PG data appeared to demonstrate variable uncertainty among stations that was not evident for the P3 data, providing incentive for the use of P3 data. This study found evidence that the SWAT model, when run using more spatially representative precipitation data (in this case, P3), was less sensitive to minor variations in model calibration parameters. Based on this initial assessment of P3 data for hydrologic modeling, bias adjustment to reduce the impact of a small number of extreme P3 precipitation values may have improved results, but was not required to produce watershed‐outlet stream flow results similar to using PG data in this study.

Select this Article		Deriving Spatially‐Distributed Precipitation Data Using the Artificial Neural Network and Multi‐Linear Regression Models Suresh Sharma, Sabahattin Isik, Puneet Srivastava, and Latif Kalin Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000617 Posted ahead of print 19 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Precipitation is the primary driver for hydrologic modeling. Since hydrologic models often require long term, spatially‐distributed precipitation datasets for calibration and validation, a novel approach was developed to generate spatially‐distributed precipitation data using the Artificial Neural Network (ANN) for the periods when NEXRAD data are either unavailable or the quality of the NEXRAD data is not good. The Multi‐Linear Regression (MLR) technique was also evaluated for completeness. The study's focus was the Saugahatchee Creek watershed in southeast Alabama. In the study area, the wet seasons are dominated by frontal precipitations, while the dry seasons primarily contain patchy, convective thunderstorms. The basic approach was to train and validate the ANN and MLR models using recent NEXRAD and rain gauge precipitations, and then use the trained model with the rain gauge precipitation data to generate past, spatially‐distributed precipitation estimates at the NEXRAD grid locations. Results showed that, for the testing period, the ANN‐simulated wet season precipitations in all the NEXRAD grids had a Nash Sutcliff Efficiency (NSE) greater than or equal to 0.72 and a Mass Balance Error (MBE) less than or equal to 14%. The same model performance parameters were 0.65 and 17% for the dry season. The MLR model did not perform as well as the ANN model. For the MLR model, the wet season MBE ranged from 13 to 48%, while the dry season MBE ranged from 0.1 to 36% on the testing dataset. An uncalibrated Soil and Water Assessment Tool (SWAT) model was used to assess the improvements in stream flow simulations with the ANN‐simulated spatially‐distributed precipitation data. It was found that the stream flow simulations using ANN‐generated, spatially‐distributed precipitations were closer to the observed stream flows as compared to stream flows generated using the rain gauge precipitations. Overall, the results suggest that the method developed in this study can be used to generate past, spatially‐distributed precipitations at NEXRAD grids locations.

Select this Article		Defining the Z∼R Relationship Using Gauge Rainfall with Coarse Temporal Resolution: Implications for Flood Forecasting Punpim Puttaraksa Mapiam, Ashish Sharma, and Nutchanart Sriwongsitanon Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000616 Posted ahead of print 19 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract This paper demonstrates a procedure for deriving the Z∼R relationship using poor temporal resolution gauge rainfall data, and evaluates its impact on runoff forecasting in the upper Ping river basin in Northern Thailand. The procedure is based on the use of a scaling logic to modify the Z∼R relationship calibrated using daily (or other coarse) resolution ground rainfall data. We demonstrate here that this scaling procedure using daily gauge data, results in radar rainfall estimates that lead to improved runoff simulations and flood forecasts for the upper Ping river basin, as compared to the case where the daily (or raw) Z∼R relationship is used, or even where the daily gauge rainfall is used by itself. This evaluation is based on hourly comparisons for the high rainfall season over a period of 3 years (2004–2006) at six point locations in the catchment. This scaling relationship has significant implications for flood modeling in most of the developing world that has weather radar coverage and a daily gauge network, but a limited continuous ground rainfall measuring network.

Select this Article		Precipitation Simulation Based on k‐Nearest Neighbour Approach Using Gamma Kernel Manish Kumar Goyal, Donald H. Burn, and C. S. P. Ojha Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000615 Posted ahead of print 19 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract This paper presents a weather generator that produces new values of precipitation to generate realistic weather sequences. The model has been applied to a network of 14 meteorological stations around the Upper Thames River Basin (UTRB), Ontario, Canada. We developed a simple model that employs the k‐nearest neighbour resampling approach with gamma kernel perturbation. This gamma kernel perturbation enables producing new values rather than merely reshuffling the historical data to generate realistic weather sequences. Daily precipitation was simulated at all the locations in and around the considered basin. The comparison of simulated data to the observed data led to the conclusion that suggested perturbation algorithm performs quite well in preserving the monthly and annual historical statistics.

Select this Article		Statistical Evaluation of Parameters in Heterogeneous Aquifers Zekai Şen and Hussam Wagdani Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000614 Posted ahead of print 19 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Transmissivity and storage estimates are questioned in laterally heterogeneous aquifers as to their representativeness of underlying assumptions in the classical aquifer test methods. For this purpose the aquifer parameter estimations are obtained by the slope matching procedure and their statistical properties are investigated. The change of lateral heterogeneity is obtained with radial distance from the well center. Frequency and distance based weighted, harmonic and geometric averages of aquifer parameter estimations are suggested in addition to the most frequently occurring (mode) estimates. The application of slope method leads to a sequence of aquifer parameter estimations, the arithmetic averages of which correspond to classical type curve match or straight‐line results. Due to the lateral heterogeneities in the geological set up, aquifer parameter estimates cannot be constant.

Select this Article		Quantifying the Uncertainty of Return Period and Risk in Hydrologic Design Jose D. Salas, M. ASCE, Jun H. Heo, Dong J. Lee, and Paolo Burlando Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000613 Posted ahead of print 17 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Concepts of risk and uncertainty are commonly used for designing and evaluating flood related hydraulic structures such as flood walls. A general framework for estimating the uncertainty of the return period and hydrologic risk is presented based on the first order analysis of uncertainty for estimating the variance of the return period and risk of failure and the method of moments (MOM), probability weighted moments (PWM), and maximum likelihood (ML) estimation methods. The general method is applicable for any underlying probability distribution function of maximum annual floods. In particular, the method is illustrated by using the exponential (1 parameter) and the Gumbel (2 parameters) distributions. The derived variance of the return period is a function of the sample size N and the non‐exceedance probability q, while that of the risk are functions of the sample size N, design life n, and nonexceedance probability q. Simulation experiments have been performed to analyze the behavior of the risk of failure for various values of the sample size, design life, nonexceedance probability, and coefficient of variation. They showed that the derived variances of the risk can be applicable for a wide range of conditions particularly for sample sizes bigger than 50 and design lives smaller or equal to 50. An example is included to illustrate the applicability of the concepts and proposed equations.

Select this Article		Comparison of Artificial Neural Network Models for Sediment Yield Prediction at Single Gauging Station of Watershed in Eastern India Ajai Singh, Mohd. Imtiyaz, R. K. Isaac, and D. M. Denis Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000601 Posted ahead of print 18 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract This paper describes the application of two different neural network models, the Standard Back Propagation (SBP) and Radial Basis Neural Network (RBNN) to predict monthly sediment yield as a function of monthly rainfall and runoff during rainy season for a watershed area in India. Four scenarios were considered to determine the type and number of inputs for the ANN Model. It was observed that in the small and forested watershed of Nagwa, inclusion of monthly precipitation and average discharge values improved the performance of ANN model in the estimation of monthly sediment yield. The momentum rate, number of nodes at hidden layer, number of nodes at prototype layer, linear coefficient, learning rule and transfer functions were optimized based on lowest RMSE and highest R values. The optimized parameters were used for SBP and RBNN model. During validation periods, RBNN model was closer to the observed values than SBP. The mean annual observed sediment yield was 3.7 t/ha. The mean annual simulated sediment yield was found to be as 3.1 t/ha and 3.5 t/ha in case of SBP during training and validation periods. RBNN simulated mean annual sediment yield as 3.6 and 3.5 t/ha during training and validation periods. Results are indicative that RBNN model is more appropriate tools for forecasting/simulating the sediment yield at single point of interest in agricultural watersheds.

Select this Article		Rapid and Approximate Hydrologic Analysis Using Web‐Based Data and Tools Lawrence Griffith, Elizabeth Bristow, and Mark Jourdan Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000561 Posted ahead of print 18 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract Preliminary site design, emergency response, or engineering operations in remote locations may require a rapid hydrologic analysis in order to provide decision‐support information on a site's suitability for various improvements. This note describes a procedure for conducting such analyses using widely available internet‐based data and tools. The purpose of this paper is to introduce the reader to the steps necessary to execute a hydrologic analysis remotely. The analysis presented was conducted using programs typically found on any computer or that can be downloaded on short notice from the internet. Freely available online geospatial data was used to create a database of hydrologic conditions at remotely identified points of interests. These points of interest were compared to actual hydrologic databases for sections of Interstate 25 in New Mexico and state highway M‐131 in Michigan. The results of the remote hydrologic analysis correctly identified and analyzed 78% of actual physical locations of culverts for the New Mexico site. Due to increased difficulty of visual identification caused by the density of land cover in a more humid climate, the remote hydrologic analysis technique correctly identified 55% of actual physical locations of culverts for the Michigan site. Potential methods to improve the accuracy of the technique are discussed.

Select this Article		Regional Intensity‐Duration‐Frequency Curves Derived from Ensemble Empirical Mode Decomposition and Scaling Property Chun‐Chao Kuo, Thian Yew Gan, F. ASCE, and Steven Chan Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000612 Posted ahead of print 16 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract Because of the large spatial variability of most precipitation data, site‐specific Intensity Duration Frequency (IDF) curves generally cannot be reliably transferred to ungauged sites, even those located nearby. Further, most municipal IDF curves of Canada are traditionally fitted to the Extreme Value type I (EVI) probability distribution (PD) with parameters derived by the Method of Moment (MOM), which are not as accurate as fitting such data to the General Extreme Value (GEV) PD with parameters derived by the probability weighted moment (PWM) method. In this study, we propose deriving regional IDF curves for Edmonton based on the scaling property of precipitation data derived using the ensemble empirical mode decomposition (EEMD) method. Selected sets of annual maximum precipitation data were first decomposed by the EEMD to intrinsic mode functions (IMFs) and the scaling property was investigated. Next, representative scale exponents were extracted from IMFs. Our results show that quantile estimates derived from GEV‐PWM are more accurate than those derived from EVI‐MOM, whose underestimation of rainfall intensity becomes obvious when the return period is over 25‐yr, especially for storms of duration less than an hour. Therefore, quantile estimates of the GEV‐PWM have been used to derive regional IDF curves for Edmonton. The results also show that for Edmonton, generally three of four IMFs of the precipitation data showed simple scaling property, and regional IDF curves derived from the scaling IDF and EEMD approach predict accurate storm intensities for rain gauging sites at both the calibration and validation stages, but there could be errors associated with predicted storms of high return periods, say, about 100‐year.

Select this Article		Effect of Land Use on Scouring Flow Hydraulics and Transport of Soil Solute in Erosion Tailong Guo, Quanjiu Wang, Wenjuan Bai, and Jie Zhuang Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000611 Posted ahead of print 16 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract We applied water flushing to different land use plots on loess slopes to examine the effect of land use changes on flow hydraulics and transport of soil surface solute in erosion. Runoff and movement of sediment and soil solute were analyzed in relation to land use and scouring flow. Flow experiments were conducted with five land use treatments: abandoned land (Salsola ruthenica), alfalfa land (Medicago sativa), corn land, scrubs land (Caragana intermedia), and bare land. The results show that at the same scouring time the cumulative sediment yields with different land use types are: bare land > corn land > caragana intermedia land > abandoned land > alfalfa land. The unit sediment loads are similar to this modulus of the cumulative sediment yields. The pre‐experiment water contents of soil profile exerted greater effect on soil moisture content and it distribution on slope than that of the antecedent solute contents in our field experiment conditions for different land use types. The land use types also affected surface transport of soil solute. The bromide concentrations in runoff were in the order of bare land > corn land > alfalfa land > caragana intermedia land > abandoned land. The nitrate concentrations in runoff with different land use types had no obvious orderliness. However, nitrate concentration was lineally related to the bromide concentration as expressed by C_NO3− = 3.01C_Br− + 28.35 (R² = 0.90).

Select this Article		Two‐Dimensional Velocity Distribution in Open Channels Using the Tsallis Entropy Huijuan Cui and Vijay P. Singh, F. ASCE Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000610 Posted ahead of print 15 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract Assuming time‐averaged velocity as a random variable, a two‐dimensional velocity distribution in open channels was derived by maximizing the Tsallis entropy, subject to mass conservation. The derived distribution was tested using field data and was also compared with other two dimensional velocity distributions. The Tsallis entropy‐based velocity distribution was found to predict the velocity near the boundary well.

Select this Article		Comparison of Computed and Experimentally Assessed Times of Concentration for a V‐Shaped Laboratory Watershed a Case Study Jin Liang and Charles S. Melching, M. ASCE Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000609 Posted ahead of print 15 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract In comparison with a kinematic‐wave based equation for estimation of the time of concentration, three methods, i.e., Ben‐Zvi's method, the modified Ben‐Zvi method, and Izzard's method were applied to determine the time of concentration from the experimental hydrographs reaching an equilibrium flow state. The experiments were performed for stationary rainstorms on a V‐shaped aluminum watershed in the Watershed Experimentation System (WES) at the University of Illinois at Urbana‐Champaign. The times of concentration determined by these three methods were compared to the mathematical equations, proposed by Woolhiser and Liggett and Wong. It is found that the time corresponding to 89% of the maximum discharge as per the modified Ben‐Zvi method yielded a generally agreeable time of concentration for the WES experimental hydrographs, while the criterion of 97% of the peak discharge as per Izzard's method overestimates the time of concentration. It is found that Woolhiser and Liggett's and Wong's equations can predict the time of concentration acceptably well for the simplified laboratory watershed with overland slopes in the range of 0.5–5% and channel slopes in the range of 0.5–3%.

Select this Article		Parameter Estimation of the Nonlinear Muskingum Flood Routing Model Using a Hybrid Harmony Search Algorithm Halil Karahan, Gurhan Gurarslan, and Zong Woo Geem Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000608 Posted ahead of print 15 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract In this paper, a hybrid harmony search algorithm is proposed for the parameter estimation of the nonlinear Muskingum model. BFGS algorithm is used as local search algorithm with a low probability for accelerating the HS algorithm. In the proposed technique, an indirect penalty function approach is imposed on the model in order to prevent negativity of outflows and storages. The proposed algorithm finds the global or near‐global minimum regardless of the initial parameter values with fast convergence. The proposed algorithm found the best solution among 12 different methods. The results demonstrate that the proposed algorithm can confidently be applied to estimate optimal parameter values of the nonlinear Muskingum model. Moreover, this hybrid methodology may be applicable to any continuous engineering optimization problems.

Select this Article		Development of a Hydrological Model for the Rio Conchos Basin Eusebio Ingol‐Blanco and Daene C. McKinney Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000607 Posted ahead of print 15 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract This paper focuses on calibration and validation of a hydrologic model of the Rio Conchos basin, a main Mexican tributary of the binational Rio Grande basin. The Rio Conchos provides about 55% of the water deliveries to the US under the 1944 water treaty signed between both countries. The hydrologic modeling has been developed using the one‐dimensional, 2 layer soil moisture accounting scheme embedded in the Water Evaluation and Planning (WEAP) model. A ten‐year period was used to calibrate the model, which was achieved by a trial‐and‐error method for the adjustment of the model parameters. The results show a Nash‐Sutcliffe coefficient of 0.84 at Ojinaga station (mouth of the basin) and 0.81 at La Boquilla; indicating good model performance. In general the model predicts well the monthly, annual, and maximum flows; but there are significant differences between the model values and undeveloped (naturalized) flows for low flow periods, especially at La Boquilla station. For model validation, a special period of ten years was used, corresponding to drought conditions in the basin. Results show a Nash‐Sutcliffe coefficient of 0.88 at Ojinaga station, with error in annual volume less than 1% on average.

Select this Article		Simplified Reference Evapotranspiration Formula Using an Empirical Impact Factor for Penman's Aerodynamic Term John D. Valiantzas Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000590 Posted ahead of print 13 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract Recently a simple algebraic formula, equivalent in accuracy to the Penman equation is derived by Valiantzas for computing evapotraspiration from readily available measured data. The derivation of the formula is based on simplifications made to the “standardized” form of the Penman equation. In this paper, a weighted coefficient is introduced accounting for different impact of the aerodynamic component at two different ranges of relative humidity. The new formula for estimating reference evapotranspiration (ET₀) is obtained by calibration using meteorological data from the CLIMWAT global data base. The performance of the new derived formula was tested under various climatic conditions using daily data for 12 weather stations obtained from CIMIS data base. For many places where reliable wind speed data are not available, another expression was also suggested. An alternative method not requiring wind data was also tested: the reduced‐set FAO‐56 Penman Monteith method according to the standardized procedure for estimating missing wind data. Comparison of the two methods not requiring wind data indicated that the proposed formula is a better option than the reduced‐set FAO‐56 Penman Monteith method to estimate ET₀.

Select this Article		Episodic Change Analysis of the Annual Flood Peak Time Series for a Flood Insurance Study Momcilo Markus, H. Vernon Knapp, Amanda Flegel, Sally McConkey, and Wilbert O. Thomas Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000604 Posted ahead of print 13 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract The decreasing annual maximum flood peaks on the Pecatonica River and other adjacent rivers and streams in the Wisconsin Driftless Area have been reported in recent studies. Various explanations for the decreasing peaks, ranging from land use to climate change, have been offered. Different explanations generally suggested different episodes or change points separating the early periods of higher peak flows from the more recent lower peak flows. This research used the Kendall‐Tau trend test with variable start years and the t‐test to detect a change point in annual flood peaks at Freeport on the Pecatonica River. The flood peak record included the peaks between 1914 and 2008, and both tests indicated that the most significant change in the Pecatonica River occurred after an episode of generally decreasing flood peaks ending in 1954. Next, in an attempt to find an explanation for the decreasing peaks, this research carried out a seasonal analysis of flood timing. The results indicated that the majority of the earlier floods occurred in late winter months, i.e., in February and particularly in March, while the more recent floods were more frequently observed later in the spring or summer. The decrease in winter flood peaks was partly explained by the decrease in snow depth and the increase in winter temperature, providing less favorable conditions for winter flooding. In turn, the decrease in winter peak flows made once smaller summer peak flows more dominant in recent years, causing the shift in flood timing. The findings were validated regionally. Similar analysis showed a significant degree of resemblance between the Pecatonica River and several streams in its vicinity.

Select this Article		Copula‐Based Pooled Frequency Analysis of Droughts in the Canadian Prairies Sara Sadri and Donald H. Burn Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000603 Posted ahead of print 13 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract This paper studies frequency analysis of drought using copula with application of regionalization in bivariate homogeneity analysis context. Monthly streamflow data from 36 non‐regulated sites were selected from the Canadian Prairies. Drought events indicated by severity and duration were extracted from monthly flow averages. A K‐means clustering algorithm was used to form initial regions. A Fuzzy C‐means algorithm was used to form the final groups of sites that meet the criteria of bivariate discordancy, bivariate homogeneity (using L‐comoments statistics), and size. Then, the application of Gumbel, Clayton, and Frank copula, from Archimedean families, for bivariate drought frequency analysis was studied. The best fitting copula was used to produce the 3‐D graphs of severity and duration changes versus joint CDF as well as joint return period. The contour plot of 5, 10, 25, 50, and 100‐year return periods for three candidate sites were obtained. To provide a point of reference for these analysis, the 3‐D graphs and contour plots using the classic bivariate frequency analysis were presented. Bivariate analysis using copula showed a shorter return period for the severe and longer droughts. Results show the importance of clear definition of drought in every scenario since ,in our example, the longest drought does not necessarily correspond to the most severe one. Another important observation of this study was that, given the average annual rainfall of a catchment, drought seem to occur in almost any region; humid or arid. However, areas with higher annual rainfall can experience shorter but more severe drought. This study is straightforward to follow and can be useful were drought prediction, planning, and education is of interest. The procedures of this study are applicable for flood frequency analysis as well. Furthermore, ungauged sites can be easily integrated in the procedure of regionalization.

Select this Article		A Linear Programming Method Considering Topographical Factors Used for Estimating Missing Precipitation Ju‐Hwan Yoo Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000602 Posted ahead of print 6 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract A new linear programming method with an option for topographical factors is developed for estimating missing precipitation. We simply assume missing precipitation depth at a base station is expressed as a linear combination of precipitation depths at neighboring index stations in the same period using weighting factors. And we introduce the topographical factor which is proportional to the weighting factor into the method. The topographical factor is associated with distance and difference in elevation between the base station and the index station. To achieve development of the method an optional constraint equation expressed as a linear combination of the topographical factors is added to the constraint set of the existing linear programming method. As a case study, two case sets of 6 stations in the Han River Basin are selected. One of 6 stations in case 1, Cheorwon, is selected as missing station and other 5 stations are used as index stations. And in case 2 Pyeongchang station is selected as missing station and other 5 stations closer to the missing station than those in case 1 are used as index stations. Linear programming methods with four different sets of optional constraints are applied to the observed precipitation data, which are annual data in case 1, and which are hourly data in case 2. Two case studies show an introduction of the topographical factors into the existing linear programming method for estimating missing precipitation makes weighting factors in the method change into those reflecting the topography of precipitation points. The developed method with an option is useful in estimating the missing precipitation values in the case of hilly regions only when the option is taken after applying four options.

Select this Article		Evaluation of MLP‐ANN Training Algorithms for Modeling Soil Pore‐Water Pressure Responses to Rainfall M. R. Mustafa, R. B. Rezaur, S. Saiedi, H. Rahardjo, and M. H. Isa Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000599 Posted ahead of print 6 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract Knowledge of pore‐water pressure responses to rainfall is vital in slope failure and slope hydrological studies. The performance of four Artificial Neural Network (ANN) training algorithms has been evaluated to identify the training algorithm appropriate for modeling the dynamics of soil pore‐water pressure responses to rainfall patterns using Multilayer Perceptron (MLP) Artificial Neural Network (ANN). The ANN model comprised 8 neurons in the input layer, 4 neurons in the hidden layer, and a single neuron in the output layer representing an 8—4—1 ANN architecture. The training algorithms evaluated include the Gradient Descent (GD), Gradient Descent with Momentum (GDM), Scaled Conjugate Gradient (SCG), and Levenberg‐Marquardt (LM). The performance of the training algorithms were evaluated using standard performance evaluation measures namely the root mean square error (RMSE), the coefficient of efficiency (E²), and the time and number of epochs required to reach a predefined accuracy. It was found that all the training algorithms could be used in the prediction of pore‐water pressures. However, the LM algorithm required the least time and epochs for training the network and gave the minimum error during both training and testing. The LM training algorithm is therefore proposed as an ideal and fast training algorithm for modeling the dynamics of soil pore‐water pressure changes in response to rainfall patterns.

Select this Article		Interpretation of Pumping Test with Radial Collector Well Using a Reservoir Model Emmanuel Kwame Appiah‐Adjei, Longcang Shu, Kwaku Amaning Adjei, Chengpeng Lu, and Mingjiang Deng Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000598 Posted ahead of print 6 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract This study proposes a reservoir model for evaluation of aquifer parameters from a long duration pumping test conducted with a radial collector pumping well and nine observation wells in an unconfined aquifer in the Tailan River basin of China. The proposed model, based on the concept of double continuum, was used to conceptualize the pumping test site into conduit and porous reservoirs coupled by a linear flow exchange for simulating flow during the pumping test. The set of model equations developed from the concept were solved by an iterative method. The model simulated hydraulic heads agree reasonably well with the observation heads in both the pumping and observation wells at an average normalized root mean square error of 10.99 % and 8.06 %, respectively, during pumping but weaker in the recovery period. This notwithstanding, the specific yield estimates compare well with the range obtained for a numerical modelling of the entire aquifer basin. Significantly, the model was applied successfully in simulating sustainable withdrawal rates from the aquifer and may be a useful tool for analysing flows to radial collector wells for applications in water resources management.

Select this Article		Erratum for “Evolution of the SCS Runoff Curve Number Method and Its Application to Continuous Runoff Simulation” by J. R. Williams, N. Kannan, C. Santhi, X. Wang, and J. G. Arnold J. R. Williams, N. Kannan, C. Santhi, X. Wang, and J. G. Arnold Journal of Hydrologic Engineering doi:http://dx.doi.org/ Posted ahead of print 6 February 2012 Full Text: \| Download PDF
		Abstract Unavailable

Select this Article		Reservoir Evaporation Prediction Using Data Driven Techniques R. Arunkumar, S. M. ASCE and V. Jothiprakash Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000597 Posted ahead of print 6 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract Evaporation in reservoirs plays a prominent role in water resources planning, operation and management, since a considerable amount of water is lost through evaporation, especially in large reservoirs. Estimating the evaporation from surface water requires ample data, usually, that are not easily measurable. At present, in India, reservoir evaporation is estimated from the pan evaporation and the average water spread area. Since, reservoir evaporation is in non‐linear relationship with the reservoir storage and other meteorological parameters, accurate prediction of evaporation by the conventional method is a cumbersome process. It has been well established that, the recently evolved data driven techniques will excel in non‐linear processes modeling. In this study, the reservoir evaporation is predicted using three different data driven techniques, namely, artificial neural network (ANN), model tree (MT) and genetic programming (GP) by time‐series modeling. The daily Koyna reservoir evaporation prediction models are developed using 49 years daily evaporation data. About 70% of the dataset is used for training the model and the remaining 30% of the dataset is used for testing. From this study, it is found that all the data driven techniques predicted the reservoir evaporation very accurately with better performance especially with a correlation around 0.99. This shows that, if the input data series exhibits a good pattern with less noise, the data driven techniques result in better performances. It is also observed that, among the data driven techniques used, GP predicts the reservoir evaporation slightly better than ANN and MT models.

Select this Article		Comparison of the Power of Log‐Normality Tests with Different Right Tail Alternative Distributions Barbara Martel, Salaheddine El Adlouni, and Bernard Bobée Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000595 Posted ahead of print 16 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract In flood frequency analysis (FFA), the adequate choice of distribution to fit data is a major problem. The three‐parameter Log‐Normal (LN3) distribution has an intermediate tail behavior between the distributions of the class C (regularly varying distributions) and those of the class D (sub‐exponential distributions). HYFRAN software performs a complete frequency analysis for about twenty distributions often used in hydrology including the LN3 and distributions of the classes C and D. A Decision Support System (DSS) was added to the HYFRAN software to become the HYFRAN‐PLUS software. It allows to distinguish between the distributions of the classes C and D. The objective of the present study is to discriminate the LN3 distribution and that of the classes C of regularly varying distributions (heavier tail) and D of sub‐exponential distributions (lighter tail) and then to improve the current version of the DSS. The power of several normality tests is evaluated for log‐transformed variates using a Monte Carlo approach for different alternative hypothesis. Jarque‐Bera test has been found the most powerful on transformed data. Results show a strong dependence between the values of the parameters and the power of the test as well as the quantile estimation errors. Results lead to the development of a LN3 goodness‐of‐fit procedure, based on the coefficient of variation, the coefficient of skewness and the Jarque‐Bera normality test. This procedure will be added to the Decision Support System of the HYFRAN‐PLUS software.

Select this Article		Saltwater Intrusion and Recirculation of Seawater at a Coastal Boundary Louis H. Motz, M. ASCE and Ali Sedighi Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000594 Posted ahead of print 16 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Numerical experiments were performed to investigate saltwater intrusion and recirculation of seawater at a coastal boundary. A field‐scale two‐dimensional cross‐section was simulated in which freshwater inflow occurred at an upgradient boundary, and saltwater inflow and freshwater outflow and recirculated seawater outflow occurred at a downgradient boundary. The upgradient boundary is a specified‐flux boundary with a zero (i.e., freshwater) concentration, and the downgradient boundary is a specified‐head boundary with a specified (i.e., saltwater) concentration. This problem was solved numerically using SEAWAT for two conditions, i.e., first for the uncoupled condition in which the fluid density is constant and thus the flow and transport equations are uncoupled in a constant‐density flowfield, and then for the coupled condition in which the fluid density is a function of the total dissolved solids concentration and thus the flow and transport equations are coupled in a variable‐density flowfield. Equivalent freshwater heads are specified at the downstream boundary for both conditions to account for density differences between freshwater and saltwater at the downstream boundary. For both conditions, it was determined that saltwater intrusion and seawater recirculation are decreased significantly as the dimensionless ratio of the freshwater inflow relative to the density‐driven buoyancy flux (a_z) is increased. However, the extent of saltwater intrusion is less and the degree of seawater recirculation is greater for the uncoupled condition compared to the coupled condition at smaller values of a_z, indicating that significant differences can occur between uncoupled and coupled simulations. For the experiments conducted in this investigation, at smaller values of a_z ̃ 0.1, where the density‐driven buoyancy flux dominates the freshwater advective flux, the extent of saltwater intrusion is less and the degree of saltwater recirculation and percent of recirculated seawater are greater for the uncoupled condition compared to the coupled condition. At larger values of a_z ̃10.0, where the freshwater advective flux dominates the buoyancy flux, the extent of saltwater intrusion for the uncoupled condition becomes equal to the extent of saltwater intrusion for the coupled condition, and the degree of saltwater recirculation and percent of recirculated seawater for the uncoupled condition asymptotically approach the corresponding values for the coupled condition.

Select this Article		An Analytical Probabilistic Model for Evaluating the Hydrologic Performance of Green Roofs Shouhong Zhang and Yiping Guo Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000593 Posted ahead of print 16 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract An easy‐to‐use and physically‐based analytical probabilistic model is developed to evaluate the long‐term average hydrologic performance of green roofs. The probabilistic models of local rainfall characteristics are introduced first, the hydrologic and hydraulic processes occurring on and inside a green roof system are then described mathematically, and the closed‐form mathematical expressions depicting the stormwater management performance of a green roof system are finally obtained by using the derived probability distribution theory. Simplifying assumptions are made to mathematically describe the hydrologic and hydraulic processes. The validity of these assumptions and the overall probabilistic approach is demonstrated by comparing its outcomes with results from a series of continuous simulations using long‐term rainfall data from Detroit, Michigan and observations from a real case study in Portland, Oregon.

Select this Article		An Improved CN‐Based Long‐Term Hydrologic Simulation Model Manoj K. Jain, Dilip G. Durbude, and Surendra K. Mishra Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000592 Posted ahead of print 16 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Employing the advanced Soil Moisture Accounting (ASMA) procedure and the modified sub‐surface drainage flow concept, a Curve Number (CN) based model, named as Modified Long Term Hydrologic Simulation Advance Soil Moisture Accounting (MLTHS ASMA) model, is proposed to simulate daily flows. Its application to 17 watersheds falling in different agro‐climatic zones of India and comparison with the existing LTHS ASMA model reveal that the proposed model yields higher efficiency, lower SE and RE values for high runoff producing wet watersheds and lower efficiency for low runoff producing dry watersheds, indicating a very good model response to wet watersheds, and good to satisfactory to dry watersheds. On most watersheds, the proposed model performed better than the existing one. In addition, CN parameters for surface and sub‐surface flows were most sensitive followed by the parameters related with soil characteristics, and the significance of base flow was greater in wet watersheds than in dry watersheds.

Select this Article		Using Local Weather Radar Data for Sewer System Modelling: A Case Study in Flanders, Belgium Toon Goormans and Patrick Willems Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000589 Posted ahead of print 14 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Contemporary sewer system operation heavily relies on urban drainage model results. In a case study near Leuven, this research investigates the potential of a cost‐effective local weather radar (LAWR, DHI Water & Environment, DK) for providing rainfall input to sewer models. Before rainfall estimation is possible, the radar was calibrated using tipping bucket rain gauge measurements. Various calibration methods were investigated, and it was found that a nonlinearly regressed power law function taking range to the radar into account is most suitable in this case study. Rainfall estimations could be slightly improved by making the calibration dependent on radar output. 57 events were simulated using the modelling software InfoWorks CS (MWH Soft Ltd., UK), and the effect of radar input on model results was investigated. Large quantitative deviations exist, but the qualitative course of time series observed in conduits is reproduced well. Although certain events show a higher correspondence between measured and simulated time series when using radar driven input, generally the gauge driven input outperforms the former, in this case study and accompanying model.

Select this Article		Understanding Precipitation Fidelity in Hydrological Modeling John T. Mobley, Teresa B. Culver, and Robert W. Burgholzer Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000588 Posted ahead of print 14 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract The objective of this research is to develop and demonstrate a methodology to specifically assess the inter‐relationships between estimated precipitation, observed stream flow, and hydrologic model performance. To satisfy this objective, this work introduces a new concept called ‘precipitation fidelity,’ which is the correspondence of stream outflow to the estimated precipitation used as input into a hydrologic model. Simple annual and daily precipitation fidelity indices are defined. The use of the precipitation fidelity indices is then demonstrated for the Rivanna Watershed in central Virginia as modeled using an existing hydrologic model, the Chesapeake Bay Program Phase 5 watershed model, and the associated precipitation input data set. The precipitation fidelity results are used in conjunction with model output to identify the effect of precipitation estimation accuracy on model performance at both long time scale and short time scales. Based on the daily precipitation fidelity measure, in the headwater watersheds, about a quarter of the days lack fidelity between the precipitation input and the observed stream flows. Days when the estimated input precipitation has runoff‐generating rainfall, but the observed stream discharge does not increase, have the highest average relative daily modeling errors and high area‐weighted daily modeling errors. These results indicate that precipitation needs to be better represented in the headwater subwatersheds. Regression analysis using the Analysis of Covariance method was used to determine statistical similarity between annual estimated precipitation and observed and modeled stream flows. Regression results suggested that direct hydrology calibration of the subwatershed of interest leads to both a higher level of correspondence between estimated precipitation and modeled flows and an acceptable ‘goodness of fit’ between the modeled and observed data.

Select this Article		Two Semi‐Distributed ANN‐Based Models for Estimation of Suspended Sediment Load Vahid Nourani, Omid Kalantari, and Aida Hosseini Baghanam Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000587 Posted ahead of print 14 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract The sediment load transported in a river is the most complex hydrological phenomenon due to a large number of obscure parameters and existence of both spatial variability of the basin characteristics and temporal climatic patterns. In this paper two Artificial Neural Network (ANN) models were developed for semi‐distributed modeling of suspended sediment load process of the Eel River watershed located in California, USA. The first model was an integrated ANN model trained by the data of multiple stations inside the watershed. In the second model, as a geomorphology‐based ANN model, space depended geomorphologic parameters of the sub‐basins, extracted by GIS (Geographic Information System) tools, accompanied by time depended meteorological data were imposed to the network. In both models, three‐layer perceptron neural networks were trained considering various combinations of input and hidden layers’ neurons and the optimum architectures of the models were selected according to the computed evaluation criteria. Furthermore, the ability of the models for spatiotemporal modeling of the process was examined through the cross validation technique for a station. The obtained results demonstrate that although the predicted sediment load time series by both models are in satisfactory agreement with the observed data, the geomorphological ANN model produces better performance than integrated model because of employing spatially variable factors of the sub‐basins as the model's inputs. Therefore, the model can operate as a non‐linear time‐space regression tool rather than a fully lumped model.

Select this Article		Temporal Moments for Reactive Transport through Fractured Impermeable / Permeable Formations Pramod Kumar Sharma, M. Sekhar, Rajesh Srivastava, and C. S. P. Ojha Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000586 Posted ahead of print 12 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Transport of reactive solutes through fractured porous formations has been analyzed. The transport through the porous block is represented by a general multi‐process non‐equilibrium equation and that for the fracture is represented by an advection‐dispersion equation with linear equilibrium sorption and first order transformation. An implicit finite difference technique has been used to solve the two coupled equations. The transport characteristics have been analyzed in terms of zeroth, first, and second temporal moments of the solute in the fracture. We first compare the solute behavior for fractured impermeable and fractured permeable formations and analyze the effects of various fracture and matrix transport parameters. Subsequently, we analyze the transport through a fractured permeable formation to ascertain the effect of equilibrium sorption, rate limited sorption, and multi‐process non‐equilibrium transport process. It was found that the temporal moments were nearly identical for the fractured impermeable and permeable formations, when both the diffusion coefficient and the first order transformation coefficient were relatively large. The multi‐process non‐equilibrium model resulted in a smaller mass recovery in the fracture and higher dispersion compared to the equilibrium and rate‐limited sorption models.

Select this Article		Assessing Severe Drought and Wet Events over India in a Future Climate Using a Nested Bias Correction Approach Richa Ojha, D. Nagesh Kumar, A. Sharma, and R. Mehrotra Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000585 Posted ahead of print 12 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract General Circulation Models (GCMs) are routinely used to simulate climate conditions for the future. However, rainfall outputs from GCMs are highly uncertain in preserving temporal correlations, frequencies and intensity distributions thus limiting their direct application for downscaling and hydrological modeling studies. To address these limitations, raw outputs of GCMs or Regional Climate Models (RCMs) are often bias‐corrected utilizing past observations. In this paper, a methodology is presented for utilizing a Nested Bias Correction (NBC) approach to predict the frequencies and occurrences of severe droughts and wet conditions across India for a 48‐year period (2050–2099) centered at 2075. Specifically, monthly time series of rainfall from seventeen GCMs corresponding to the SRES A2 emission scenario are utilized to draw conclusions for extreme events. An increasing trend in frequencies of droughts and wet events is observed. The northern part of India and coastal regions show maximum increases in the frequency of wet events. Drought events are expected to increase in the West central, Peninsular and Central Northeast regions of India.

Select this Article		Regional Flood Frequency Analysis: How We Got Here and Where We Are Going David R. Dawdy, M. ASCE, F. AGU, Veronica W. Griffis, M. ASCE, and Vijay K. Gupta, F. AGU Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000584 Posted ahead of print 12 January 2012 Full Text: \| Download PDF
		Abstract Unavailable

Select this Article		Closed Form Theoretical Solution for Finite Depth Seepage below Flat Apron with Equal End Cutoffs and a Downstream Step Arun K. Jain and Lakshmi N. Reddi, M. ASCE Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000583 Posted ahead of print 12 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract The paper gives a closed form theoretical solution for the steady seepage below flat horizontal impervious apron of a hydraulic structure with equal end cutoffs, with a step at downstream end, and founded on pervious medium of finite depth. This is obtained by using Schwarz‐Christoffel transformation in two stages. The numerical solution of the resulting implicit equations involving elliptic integrals gives the uplift pressures at key points, seepage discharge factor and exit gradient factor in terms of non‐dimensional floor profile ratios. Design charts have been given for these seepage characteristics.

Select this Article		A Review of Advances in Hydrologic Science in China in the Last Decades: Impact Study of Climate Change and Human Activities Tao Yang, Qiang Zhang, Weiguang Wang, Zhongbo Yu, Yongqin David Chen, Guihua Lu, Zhenchun Hao, Alexander Baron, Chenyi Zhao, Xi Chen, and Quanxi Shao Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000582 Posted ahead of print 12 January 2012 Full Text: \| Download PDF
		Abstract Unavailable

Select this Article		Using Hydrologic Simulation to Explore the Impacts of Climate Change on Runoff in the Huaihe River Basin of China J. Y. Zhang, G. Q. Wang, Thomas C. Pagano, J. L. Jin, C. S. Liu, R. M. He, and Y. L. Liu Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000581 Posted ahead of print 11 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Climate change has become an environmental issue of utmost importance, and one which will challenge existing water resource management practices in many ways. The Huaihe River, which is one of China's major rivers, is frequently subject to flooding and drought and, for the purposes of assessing the implications of climate change on water resources in the Huaihe River basin, the Variable Infiltration Capacity (VIC) model with a resolution of 0.5°×0.5° was calibrated using data from 11 well gauged sub‐basins. The model parameters from the well gauged stations were then transferred to poorly gauged areas, according to similarities in climate conditions, soil texture etc. The calibrated VIC model was subsequently used to study the potential impacts of three climate change scenarios on basin runoff, taking projected runoff for 1961–1990 as the baseline. In general, the results showed that although the annual runoff will likely increase across the basin under the different scenarios, regional flooding and regional shortage in water resources will be exacerbated under the impacts of global warming.

Select this Article		The Influence of River Sinuosity on the Distribution of Conservative Pollutants Heqing Huang, Guang Chen, and Qian‐Feng Zhang Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000580 Posted ahead of print 11 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract The influence of river sinuosity on the distribution characteristics of pollutants in a wide river is investigated three‐dimensionally with a numerical model. It is found that for a meandering river the hydrodynamic force strongly controls the distribution of a conservative pollutant in the river. Due to the secondary flow at a channel bend, high sinuosity leads to a lighter‐than‐water pollutant concentrating more on the inner bend apex region at the surface, while at a deep near‐bed region on the contrary, it concentrates more on the outer bend apex. For a heavier‐than‐water pollutant, two unique features of gravity flows in sinuous channels: super‐elevation and multi‐cell cross‐sectional secondary flows with alternate circulation directions lead it to be distributed at the bottom more on the inner bend apex region while more on the outer bend apex region at a depth corresponding to the mixing region of the bottom two secondary flow cells of opposite circulation direction. These findings may assist field investigations in locating the best sampling points and for cost‐effective measures to be taken for accidental or planned waste‐discharge river pollution events.

Select this Article		Continuous Forecasting and Evaluation of Derived Z‐R Relationships in a Sparse Rain Gauge Network Using NEXRAD Samuel H. Rendon, Baxter E. Vieux, and Chandra S. Pathak Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000579 Posted ahead of print 11 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Distributed rainfall information is necessary for making operational hydrologic predictions and for retrospective studies. Rainfall measurements from radar require conversion of reflectivity into rainfall rates, but are known to contain systematic errors, or bias. Default Z‐R relationships commonly used are not adapted to particular radars and are known to vary by season. By deriving Z—R relationships, improved rainfall estimation may be obtained for a given season and radar installation. These derived Z‐R relationships are used before prospective storms cross over gauges within a network, i.e. before near real—time bias corrections are possible. This research focuses on the derivation of Z‐R relationships for rainfall estimation in the South Florida Water Management District. These relationships are derived through seasonal characterization of gauge and radar observations. The verification of the derived Z‐R relationships is evaluated using rain gauges withheld for cross validation. Methods used in forecasting include persistence, seasonal trends, autoregressive, and Kalman Filter methods. Results demonstrate that radar—specific Z—R relationships exhibit better efficiency than using standard Z‐R relationships, and that among the forecasting methods tested, all showed advantage over persistence with varying degrees of accuracy.

Select this Article		Hydrological Response of Sloping Farmlands with Different Rock Fragment Covers in the Purple Soil Area of China Xiaoyan Wang, Zhaoxiao Li, Chongfa Cai, Zhihua Shi, Qinxue Xu, Zhiyong Fu, and Zhonglu Guo Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000576 Posted ahead of print 11 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract In the mountainous area of China, the rock fragments in top soils are often removed by farmers because of their side effects on tillage. In order to understand hydrological processes and assess the risk of soil erosion in purple soil areas with sloping farmlands, we investigated the effects of rock fragment cover on surface runoff, infiltration, subsurface runoff and erosion under field conditions using a portable rainfall simulator. Experimental twin plots (two subplots with 1‐m wide by 2‐m long, 32% slope) with different rock fragment covers ranging from 0% to 42% were exposed to four rainfall intensities: 45.5±1.9 mm/h (I1), 60.3±3.6 mm/h (I2), 92.0±4.1 mm/h (I3) and 123.9±9.4 mm/h (I4). Surface runoff, subsurface runoff, soil moisture and sediment were measured. The results show that the hydrological response was influenced by the rock fragment cover and rainfall intensity. The rate of surface runoff in bare soils was affected by the rainfall intensity and increased with increasing rainfall intensity. The values of the surface runoff rates in bare soils were lower than 70 mm/h under the I1, I2 and I3 rainfall intensities. As the rock fragment cover increased, the surface runoff rate decreased, while the infiltration rate, the subsurface runoff rate and the deep percolation coefficient increased. On the other hand, when the surface runoff rates in the bare soils were higher than 70 mm/h (in rainfall of I4), there were no significant differences in these hydrological variables among soils with different rock fragment covers. The differences in hydrological variables among soils with varying rock fragment covers decreased with increasing rainfall intensity. The rock fragment cover determined the erosive response. As the rock fragment cover increased, the sediment concentration decreased. The presence of surface rock fragments reduces soil erosion significantly, and the relationship between the soil erosion rate and rock fragment cover can be expressed by an exponential function with a high degree of reliability for different rainfall intensities. However, the effectiveness of rock fragment cover in reducing soil erosion decreased with increasing rainfall intensity.

Select this Article		Environmental Flow Components for Measuring Hydrologic Model Fit during Low Flow Events John T. Mobley, Teresa B. Culver, and Robert W. Burgholzer Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000575 Posted ahead of print 11 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract The Indicators of Hydrologic Alteration (IHA) is a statistical flow methodology for characterizing ecologically important stream flows. Typically, IHA has been used to identify the extent of human impacts on a stream's hydrology and to set management goals to restore the stream ecology. In this work, we extend the use of the seven “extreme low flow” statistics of IHA to the evaluation of the performance of a hydrologic simulation model under low flow conditions. Specifically, this work uses the IHA framework to evaluate the accuracy of the Chesapeake Bay Program Phase 5 (CBP5) watershed model during low flow events on a regional scale that is relevant to many water supply planners and managers. Because the CBP5 model's primary focus is predicting the Bay's water quality, the measures used to calibrate the CBP5 model focused primarily on the calibration of the entire hydrological record and had only secondary emphasis on specific flow regimes, such as low flows and very low flows, although these flows are important for both stream ecologies and water supply planners. To provide a comparative performance benchmark, the performance of the simple Drainage Area Ratio (DAR) method relative to the IHA low flow statistics is also determined. This paper demonstrates the use of IHA statistics for model evaluation in a case study, the Rivanna River watershed, a subcatchment within the Chesapeake Bay drainage. For rivers with a large proportion of unregulated flow contributions, we conclude that the computationally simple DAR model with appropriate surrogate watershed generally characterizes the extreme low flow conditions slightly more accurately than the CBP5 model. However, unlike the CBP5 model, the DAR model predicts future flows based solely on historical data, and thus the DAR model cannot predict flow impacts caused by hydrological alterations, thus limiting its use in water supply management. Nevertheless, our IHA analysis suggests that incorporation of a low‐flow‐specific metric into the CBP5 calibration could improve its utility for water supply management and planning at a regional scale.

Select this Article		Artificial Neural Network Based Drought Forecasting Using a Nonlinear Aggregated Drought Index S. Barua, Ph.D., Aff. M. ASCE, A. W. M. Ng, Ph.D., and B. J. C. Perera, Ph.D. Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000574 Posted ahead of print 11 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Drought forecasting plays an important role in planning and management of water resources systems, especially during dry climatic periods. In this study, a nonlinear aggregated drought index (NADI) was developed first to classify the drought condition of a catchment considering all significant hydro‐meteorological variables that have effects on droughts. An artificial neural network (ANN) based drought forecasting approach was then developed using the time series of NADI to forecast NADI values. In forecasting future drought conditions, the NADI produces the overall dryness within the system as compared to the traditional forecasting of rainfall deficiency, which considers only the meteorological droughts. Two ANN forecasting models namely, recursive multi‐step neural network (RMSNN) and direct multi‐step neural network (DMSNN) were developed in this study. Overall, these models were capable of forecasting drought conditions well up to 6 months ahead forecasts, which were statistically significant at 1% level. Moreover, it was found that both models showed the same performance for 1 month lead time forecasts. The RMSNN model had given slightly better forecasts than the DMSNN model for lead times of 2 to 3 months, and the DMSNN model had produced slightly better forecasts than the RMSNN model for forecast lead times of 4 to 6 months. Beyond the forecast lead time of 6 months, poor forecasts were observed. A comparative study was conducted to investigate the effectiveness of ANN based drought forecasting models over an Autoregressive Integrated Moving Average (ARIMA) model (which is a traditional linear stochastic model), and the results showed that both RMSNN and DMSNN models performed better than the ARIMA model.

Select this Article		Prediction of Rainfall‐Runoff in an Ungauged Basin: A Case Study in the Mountainous Region of Northern Thailand T. Piman and M. S. Babel Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000573 Posted ahead of print 11 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract The reduction of uncertainty in hydrologic predictions is important for water resources development and management, especially in ungauged basins. The objective of this study was to predict rainfall and runoff in an ungauged basin located in a mountainous region of Northern Thailand using a weather radar to estimate rainfall and a modeling approach to simulate rainfall‐runoff processes. The calibrated Z_e‐R relationship (Z_e = 18R^1.45) was used to estimate rainfall over a gauged basin and an assumed ungauged basin. The runoff simulations in the gauged and ungauged basins were carried out using the quasi‐distributed hydrological model, HEC‐HMS. The simulation results in the gauged basin, for both calibration and verification, were in agreement with the observed data. Model parameters in the assumed ungauged basin were estimated using the transposition and regionalization techniques. The predicted direct runoff hydrograph in the assumed ungauged basin using radar measured rainfall and the regionalization technique matches well with the measurements at the basin outlet. Based on the study results, it was concluded that the radar rainfall estimates and the regionalization of the hydrologic model parameters are promising alternatives for improved hydrologic predictions in ungauged basins.

Select this Article		Empirical Investigation of Curve Number Method Parameters in the Mediterranean Area Francesco D'Asaro and Giovanni Grillone Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000570 Posted ahead of print 6 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract The Curve Number (CN) method is widely used as technique for estimating surface runoff depth from rainstorms. This simply lumped method is based on the main parameter CN, which represents the lumped expression of basin absorption and on a parameter that represents the interception, the infiltration during the early part of a storm and the surface depression storage, called initial abstraction. In this paper CN is evaluated at basin scale from rainfall‐runoff multi‐daily events, in the observation period 1940–1997 (record length mean equal to 20 years), for 61 Sicilian basins with three different methods: NEH4 method, Asymptotic fitting method, Least Squares method. A first analysis of Sicilian watersheds behavior indicates a major occurrence of standard CN response (43 basins), rather than complacent response (10 basins) and a few cases of violent behavior (3 basins). For basins with complacent behavior a modified formula of runoff curve number equation is proposed. The original assumption of the Initial abstraction ratio (Ia/S or λ) equal to 0.20 is investigated for watersheds with standard and violent CN response, using “natural” and “ordered” rainfall‐runoff data. Results indicate a median λ value of 0 for natural data and 0.05 for ordered data, according to recently worldwide researches. CN seasonal preliminary analysis indicates higher curve numbers in the dormant season rather than in the growing season, while λ seasonal analysis indicates values close to 0 both in the dormant and in the growing season.

Select this Article		A Semi‐Distributed Hydrologic Model for Flood Risk Assessment in the Pejibaye River Basin (Costa Rica) Carlos de Gonzalo, José C. Robredo, and Juan Á. Mintegui Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000568 Posted ahead of print 6 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract A semi‐distributed hydrologic model, designed with the HEC‐Hydrologic Modelling System, and addressed to flood risk assessment, is presented. The model has been applied and calibrated, by means of a Multi‐step Calibration Scheme, to the Pejibaye River Basin, in a series of flash flood events that occurred between 2006 and 2009. The model consists of a rainfall‐runoff module (SCS‐CN method), a surface runoff routing module (Unit Hydrograph method), a baseflow module (linear reservoir method), and a channel routing module (Muskingum‐Cunge method). Two different unit hydrographs were contrasted (SCS and Clark) and two different approaches were used for average rainfall estimation: the Thiessen Polygons and the Inverse Distance Weighted method. Model parameters were initially estimated using classical formulation and documentation, and afterwards compared with calibrated parameters. Clark's Unit Hydrograph presented lower prediction errors, especially when combined with the Inverse Distance Weighted method. Rainfall‐runoff and baseflow methods showed a stable and reasonable behaviour. Rainfall input was highlighted as a major source of error. However, the Inverse Distance Weighted method was noted to slightly reduce timing errors, compared with the Thiessen Polygons method. Overall, the model reproduced reasonably the flash floods herein analysed, both in calibration and validation (R² between 0.81 and 0.87; Nash‐Sutcliffe between 0.70 and 0.80), and therefore could be also suitable for other watersheds with similar climatic and geomorphologic conditions.

Select this Article		Hydrologic Effects of Size and Location of Fields Converted from Drained Pine Forest to Agricultural Cropland Hyun Woo Kim, Devendra M. Amatya, George M. Chescheir, Wayne R. Skaggs, and Jami E. Nettles Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000566 Posted ahead of print 2 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Hydrological impacts of land use change are of great concern to ecohydrologists and watershed managers, especially in the Atlantic coastal plain of the southeastern US. The concern is due to rapid population growth and the resulting pressure to develop forested lands. Many researchers have studied these impacts in various scales, with varying results. The DRAINWAT model, calibrated with 1996–2000 data, was used to evaluate long‐term hydrologic effects of conversion to agriculture (corn‐wheat‐soybean cropland) of a 29.5 km² intensively managed pine‐forested watershed in Washington County in eastern North Carolina, USA. Fifty years of weather data (1951 to 2000) from a nearby weather station were used for simulating hydrology to evaluate effects on outflows, evapotranspiration, and water table depth compared to the baseline scenario. Other simulation scenarios were created for each of five different percentages (10%, 25%, 50%, 75%, and 100%) of land use conversion occurring at upstream and downstream locations in the pine forest watershed. Simulations revealed that increased mean annual outflow was significant (α = 0.05) only for 100% conversion from forest (261 mm) to agricultural crop (326 mm), primarily attributed to a reduction in evapotranspiration. While the high flow rates > 5 mm day⁻¹ increased from 2.3% to 2.6% (downstream) and 2.6% to 4.2% (upstream) for 25% to 50% conversion, the frequency was higher for the upstream location than the downstream. These results were attributed to a substantial decrease of soil hydraulic conductivity of one of the dominant soils in the upstream location that is expected after land use conversion to agriculture. As a result, predicted subsurface drainage decreased, and surface runoff increased as soil hydraulic conductivity decreased for the soil upstream. Our results indicate that soil hydraulic properties resulting from land use conversion have a greater influence on hydrologic components than the location of land use conversion.

Select this Article		Development of Jamuneswari Flood Forecasting System ‐ A Case Study in Bangladesh Md. Mizanur Rahman, N.K. Goel, and D.S. Arya Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000565 Posted ahead of print 23 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract A flood forecasting system has been developed using MIKE11 rainfall‐runoff (RR or NAM: Nedbor‐Afstromnings‐Model), hydrodynamic (HD) and flood forecasting (FF) modules in Jamuneswari river catchment of the northwestern part of Bangladesh. The 3‐arc second Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) version‐4 and the D8 method of ArcGIS9.3 have been used to delineate river network and catchment bounderies, which are required for MIKE11 model setup. European Centre for Medium‐Range Weather Forecast (ECMWF) model forecasted rainfall data have been used in MIKE11 NAM ‐ HD modules to increase the forecast lead‐time upto 72 hours. The errors of forecast results have been assessed by computing efficiency index, coefficient of correlation, volume error, peak error, and peak time error. Integration of MIKE11 HD module with MIKE NAM module has improved the result by 10.84 % of efficiency index, 20.7 % of volume error, 25.61% of peak error, and 95.83% of peak time error. MIKE11 FF module has been applied along with integrated MIKE11 NAM and HD modules to minimize the error in the forecasted result. The efficiency index, volume error, peak error, and peak time error of hindcast result, before updating by MIKE11 FF, have been calculated as 0.803, 0.505%, 2.58%, and 2 hours and after updating by MIKE11 FF module results have been calculated as 0.989, ‐0.005%, 0.158%, and 0.00 hours. Inputting the ECMWF forecasted rainfall, the updated forecasting system has determined the efficiency index, volume error, peak error, and peak time error as 0.92, 0.008 %, 0.87%, and 0.00% for 24 hours; 0.87, 0.231%, 0.507%, and 0.00 hours for 48 hours; and 0.84, 0.519%, and 0.000 hours for 72 hours. The steps of developing this flood forecasting system under this case study are generic and can be used in similar geographic condition in the world. In Bangladesh, the decision makers will get more duration to response the flood using the increased forecast lead time from this case study.

Select this Article		Uncertainty of the Assumptions Required for Estimating the Regulatory Flood: The Case of the Red River of the North Paul E. Todhunter Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000560 Posted ahead of print 14 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Federal guidelines specify the log‐Pearson type III (LPT3) distribution as the basis for the estimation of the 100‐year peak discharge that serves as the regulatory flood for floodplain management in the United States. The LPT3 distribution has been shown to provide a reasonable and flexible model of flood risk. Use of the LPT3 distribution involves a number of explicit assumptions about the annual maximum series that are often implicitly assumed in flood frequency analysis studies of individual stations, but not shown directly to be satisfied. In this case study I examine the validity of these assumptions for the Red River of the North‐Grand Forks gaging station. None of the four examined assumptions are satisfied completely. The stationarity assumption is not met, as the regional climate samples two separate climatic modes; the peak discharge time series is not a random and independent set of events; the precipitation‐runoff relationships are not uniform over time; and the flood peaks result from two flood‐causing mechanisms. It is recommended that the validity of the explicit assumptions of the LPT3 distribution be demonstrated directly as a standard step in flood frequency analyses, both as a means of advancing estimation of the regulatory flood, and as a way to better inform decisions by floodplain managers and decision‐makers.

Select this Article		Identifying Contributions of Climate Change and Human Activity to Changes in Runoff Using Epoch Detection and Hydrologic Simulation G. Q. Wang, J. Y. Zhang, T. C. Pagano, J. L. Jin, and C. S. Liu Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000559 Posted ahead of print 14 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Runoff in major rivers in China has been decreasing in recent decades. The attribution of hydrologic variability to human activity or climate change is a challenging problem and an active research area. In this study, a sequential cluster analysis method was used to detect undisturbed parts of the record for the Kuyehe River catchment in China. The Variable Infiltration Capacity (VIC) land surface model was calibrated and verified using observed hydrometeorological data from a period with relatively little human‐induced disturbance. The calibrated VIC model was then used to simulate natural runoff during the human‐regulated period. Results indicate that the recorded runoff at Wenjiachuan station had significant decline trend of −1.34mm/year. Time series of runoff was detected and divided into three epochs at two critical years of 1980 and 1998. The VIC model performed well in simulating monthly discharges in the catchment, both NSE critera in calibration (1955–1969) and verification (1970–1979) were above 70% while REs were less than 5%. Human activity was the main driver behind 68% of the runoff reduction that occurred for the period of 1980 to 2008.

Select this Article		Detention Storage over 2D Laboratory Watersheds at Concentration Time Arie Ben‐Zvi, F. ASCE Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000558 Posted ahead of print 14 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Water balances, for 2D laboratory experiments with long‐duration rainfalls over planar aluminum surfaces, indicate that at time of concentration the detention storage comprises about 70% of the accumulating inflow. Under the applied experimental conditions, its spatially averaged depth is 1 to 6 mm. This depth increases with rainfall intensity and decreases with main watershed slope. The time of concentration is defined here from rainfall commencement till the outflow begins a gradual approach towards the equilibrium state. It was shown, in an earlier paper, that the ratio of peak runoff discharge to rate of supply due to rainfall of a shorter duration is linearly related to the ratio of rainfall duration to time of concentration. Such a relation led to the formulation of the 120‐year old Rational Formula, commonly used for hydrologic design of populous districts. The similarity between laboratory and field results allows considering the detention depths in the laboratory as fairly representing the depths over outdoor impervious surfaces.

Select this Article		Use of Storms Life Cycle Information and Lightning Data in Radar‐Rainfall Estimation Emmanouil N. Anagnostou, Chandra S. Pathak, and Carlos A. Morales Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000557 Posted ahead of print 14 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Correcting real‐time radar rainfall estimates for mean‐field systematic errors (bias) is normally accomplished through gauge‐based adjustment procedures. In this study, we explore two auxiliary data sources derived from cloud‐to‐ground (CG) lightning measurements and a storm tracking applied on radar images in terms of providing microphysical information useful in improving the efficiency of gauge‐based bias adjustment techniques. The CG information is used to classify storms into thunderstorms (T‐storms) vs. showers (i.e. storms without lightning) and the tracking algorithm to classify storms according to their maturity stage (i.e. growing, mature and decay). Data for this study are based on high‐resolution radar rainfall estimates (2‐km spatial grid resolution at 15‐min intervals) available over the South Florida Water Management District for a period of eleven months along with corresponding rain gauge measurements from 120 gauges and CG occurrences from the National Lightning Detection Network. The radar error analysis for T‐storms vs. showers and for the different storm maturity stages indicate that storm tracking and CG contains significant microphysical information that can improve radar rainfall estimation. It is shown that radar rain estimates tend to underestimate convective rainfall, mainly associated with the growing stage of the storms or the occurrences of CG lightning; showers and storms at mature or decay stages is shown to be better represented by the standard Z‐R relationships used for convective and tropical storms in Florida. Results from this study indicate that storm maturity stage information derived from tracking radar images, and to a lesser significance CG observation, can be used to reduce variability in the Z‐R conversion, and consequently improve accuracy in real‐time radar rainfall estimation.

Select this Article		An Innovative Trend Analysis Methodology Zekâi Şen Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000556 Posted ahead of print 14 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Hydro‐meteorological time series include recent trends, especially over the past 30 years, as a result of climate change impact according to Intergovernmental Panel on Climate Change (IPCC). Although there are commonly used trend identification techniques such as Mann‐ Kendall (MK) and Spearman's Rho (SR) tests, their validity is possible under a set of restrictive assumptions such as independent structure of the time series, normality of the distribution and length of data. It is also not possible to calculate trend magnitude (slope) except through regression approach, which brings additional assumptions for the theoretical validation in practical applications. This paper presents a new methodology on the basis of sub‐section time series plots derived from a given time series on a Cartesian coordinate system. In such a plot trend free time series sub‐sections appear along the 45° straight‐line. Increasing (decreasing) trends occupy upper (lower) triangular areas of the square area defined by the variation domain of the variable concerned. The validity of this new approach is documented through a set of Monte Carlo simulations by taking into consideration independent and dependent processes. In the new approach, all the aforementioned assumptions in the MK and SR tests are avoided and additionally it is possible to calculate trend magnitude from square area plots. The application of this methodology is given for a set of precipitation and runoff time series from different parts of the world.

Select this Article		Influence of Solid Particle Parameters on the Sound Speed and Attenuation of Pulses in Acoustic Discharge Measurements (ADM) L. I. Costa, G. Storti, B. Lüscher, P. Gruber, and T. Staubli Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000555 Posted ahead of print 14 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Acoustic discharge measurement devices (ADM) based on transit time measurements are widely used to measure water flow rates in channels and closed conduits for hydropower applications. In addition to making velocity and discharge measurements, the ADM simultaneously records the speed of sound and the attenuation of the acoustic pulse through the water‐sediment mixture. This information can be used to estimate characteristics of the suspension such as the volume fraction of the sediment. Such information is crucial in hydropower plants because of the negative effects solid particles can have on the equipment. In this work, the Atkinson‐Kytömaa model for monodisperse particles is applied to analyze the effect of solid particles and other operating parameters on the sound speed and attenuation in water suspensions. This model has been selected because it is suitable for the interested range of applications. The model has been validated by measurements with different particle material (glass, quartz, calcium carbonate), size, size distribution, shape and concentration. Moreover, the sensitivity of the model to the particle parameters has been investigated and the critical parameters for monitoring applications have been identified.

Select this Article		One Dimensional Pollutant's Advective Diffusive Transport from a Varying Pulse ‐ Type Point Source through a Medium of Linear Heterogeneity Premlata Singh, Sanjay Kumar Yadav, and Naveen Kumar Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000553 Posted ahead of print 14 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Analytical solutions of one — dimensional advection — diffusion equation are obtained subject to initially pollutant free domain and varying pulse ‐ type input condition. The medium is considered heterogeneous and of semi‐infinite extent. The heterogeneity is defined by considering the velocity a spatially dependent linear non‐homogeneous increasing function. It is interpolated in a finite domain in which concentration values are to be evaluated. Unsteadiness of exponential form of velocity and dispersivity is also considered. The expression for velocity is written in degenerate form. Analytical solutions are obtained when dispersivity depends upon the velocity. Laplace Integral Transform technique has been used.

Select this Article		A Diffusive‐Wave Based Hydrologic‐Hydraulic Model with Sediment Transport I: Model Development D. López‐Barrera, P. García‐Navarro, P. Brufau, and J. Burguete Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000552 Posted ahead of print 7 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract In this paper, a distributed numerical model is proposed based on: (1) A hydrologic model for the water exchange laws. (2) A surface runoff model based on a hybrid two dimensional (2D) Diffusive/Kinematic Wave approximation able to calculate flow over all kinds of wet/dry ground surface slopes. (3) A groundwater flow model based on the 2D Darcy law for both saturated and partly saturated zones. (4) A 2D Hillslope Erosion Model for the sediment transport. (5) An explicit finite volume discretization with specific schemes according to the characteristics of the flow equations, upwind for the hyperbolic equations and centered for the parabolic equations. The resulting model offers a variable time step ensuring numerical stability with the time step size sensitive to the grid cell size in the Diffusive Wave case and an entropy correction of the upwind fluxes to ensure conservative solutions near local maxima in the slopes controlling the water movement. The validation and practical application of the model is presented in a companion paper in which the potential usefulness of the proposed model is demonstrated.

Select this Article		A Diffusive‐Wave Based Hydrologic‐Hydraulic Model with Sediment Transport II: Validation and Practical Application D. López‐Barrera, P. García‐Navarro, P. Brufau, and J. Burguete Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000551 Posted ahead of print 7 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract The development of a distributed two‐dimensional (2D) hydrologic‐hydraulic simulation model was presented in a companion paper. The simulation model combined overland flow (Kinematic/Diffusive Wave models), hillslope sediment transport, and groundwater flow apart from the water exchange mechanisms between zones. Particular attention was paid to the upwind discretization of the surface flow equations. In this paper, the proposed model is validated using 4 test cases with exact solutions, one academic test case, and two laboratory test cases. The model adequately reproduced front advance over dry beds of any slope and water table evolution in simple cases. As practical application of the model, the simulation of real events in two experimental basins also is presented. The work is focused on the influence of the choice of the empirical parameters on the model results concerning solid and liquid discharges. Also, due to the lack of information referring the boundary and initial conditions of the groundwater flow in real basins it is difficult to evaluate the accuracy of the complete model.

Select this Article		Case Study: Bayesian Uncertainty Analysis of the Distributed Hydrological Model HYDROTEL Médard Bouda, Alain N. Rousseau, Brou Konan, Patrick Gagnon, and Silvio J. Gumiere Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000550 Posted ahead of print 7 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract In this study, a Bayesian, inference‐based, Markov‐Chain‐Monte‐Carlo (MCMC) method coupled with an autoregressive moving average (ARMA) error model framework was used to assess the uncertainty of the process‐based, continuous, distributed hydrological model HYDROTEL when simulating daily stream flows. The uncertainty analysis was performed, as a case study, in two distinct watersheds (Montmorency, Quebec, Canada, and Sassandra, Ivory Coast, West Africa). The MCMC uncertainty analysis showed to be effective, primarily with respect to the fulfillment of the statistical assumptions of the error model. The results of the uncertainty analyses demonstrated that almost 95% of the observed daily outlet flows were bracketed by the 95%‐prediction uncertainty bands. This indicates that the parameter uncertainty associated with the ARMA error model could reach the prediction uncertainty. Also, it was possible to mimic the prediction uncertainty using only the most sensitive model parameters for the Montmorency and Sassandra watersheds. The uncertainty framework, as presented herein, may be applied to any distributed, continuous, hydrological model such as HYDROTEL. Given sufficient computational resources, such framework could become quite useful in providing uncertainty bands within the scope of predicting inflows to reservoirs for subsequent planning and management purposes.

Select this Article		Long‐Term Eddy Covariance Monitoring of Evapotranspiration and Its Environmental Factors in a Temperate Mixed Forest in Northeast China Xinjian Zhang, Changjie Jin, Dexin Guan, Anzhi Wang, Jiabing Wu, and Fenghui Yuan Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000549 Posted ahead of print 8 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract On the basis of eddy covariance measurements, we present the results of three years (2005–2007) of direct evapotranspiration (ET) measurements over a mixed temperate forest in Northeast China. The diurnal and seasonal variations in ET and its main driving factors were analyzed. Annual ET values for the forest were 437, 506, and 632 mm in 2005, 2006, and 2007, respectively. The contribution of ET during the dormant season was not negligible, ranging from 17% to 23% of the annual ET for the study years. On an annual course, the increase in ET is associated with the increasing air temperature (T_a) and plant growth in late April and early May, peaking in July or August with monthly mean rates of 2.9 mm day⁻¹ (July 2005), 3.4 mm day^‐1 (July 2006), and 3.8 mm day^‐1 (August 2007). Priestley‐Taylor parameter α also varied seasonally, with its minimum and maximum values occurring in the dormant and growth seasons, respectively. During the growth season, the values of α were generally between 0.6 and 0.9, indicating that the vapor pressure deficit was the main factor affecting ET. In addition, canopy conductance (g_c) also drove the ecosystem ET. Our results show that no significant soil water stress in the growth season was observed at the study site. On an annual basis, the ratio of ET to precipitation was 74.3%, indicating that ET was the main water loss component of water balance in the temperate forests of Northern China.

Select this Article		A Hybrid Optimization Rainfall‐Runoff Simulation Based on Xinanjiang Model and Artificial Neural Network Xiao‐meng Song, Fan‐zhe Kong, Che‐sheng Zhan, and Ji‐wei Han Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000548 Posted ahead of print 25 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract A hybrid rainfall‐runoff model that integrates artificial neural networks (ANNs) with Xinanjiang (XAJ) model was proposed in this study. We extracted the digital drainage network and sub‐catchments from DEM (digital elevation model) data considering the spatial distribution of rain‐gauge stations. And then the semi‐distributed XAJ model was established based on DEM. Considering the runoff routing cannot be calculated by the linear superposition of the route runoff from all sub‐catchments, artificial neural networks as effective tools in nonlinear mapping are employed to explore nonlinear transformations of the runoff generated from the individual sub‐catchments into the total runoff at the entire watershed outlet. The integrated approach has been demonstrated feasible and was applied successfully in the Yanduhe watershed, the upper tributary of Yangtze River Basin. And the results indicated that the approach of integrating BP ANN with semi‐distributed XAJ model may achieve the promising results with acceptable accuracy for flood events simulation and forecast.

Select this Article		The Link between Flow Regime and the Catchment Hypsometry: An Analysis of South Australian Basins Shermi P. Liyanagamage and Guna A. Hewa Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000547 Posted ahead of print 25 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract The quantitative analysis of the Hypsometric Integral (HI) and other statistical moments (e.g. kurtosis and skewness) of hypsometric curve conducted using a total of 195 main catchments and 223 sub‐catchments from South Australia, we reveal that most of the study catchments are at either young or mature stage of landscape development which indicates that they are at a high risk of future erosion if disturbed by anthropogenic activities. Results of this study indicated significant correlations among hypsometric attributes confirming the relationships proposed by previous studies between landscape features and hypsometry. No significant correlation between hypsometric characteristics (HI, Poly skew, etc.) and selected flow statistics (mean (μ), coefficient of variation (cv), lag‐one auto correlation coefficient (r₁) and Q50–Q10 range flow duration values) were found for South Australian catchments. In contrary to some of the previous study outcomes, no significant vertical and horizontal scale dependency of the HI was observed in this study. Some further study recommendations are provided under the conclusion.

Select this Article		Impact of Climate Change on Streamflow and Soil Moisture in the Vermilion Basin, Illinois, USA Mohsen Tavakoli and Florimond De Smedt Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000546 Posted ahead of print 17 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract Potential effects of climate change on streamflow and soil moisture in Vermilion basin, Illinois, USA, are investigated using a spatial distributed hydrological model (WetSpa). The model results show a good agreement between observed and simulated discharge at Leonore gauge station and soil moisture at Stelle soil moisture recording site. Climate scenarios are derived by statistical downscaling of regional climate predictor variables for two climate scenarios and four time periods. The downscaled local climate variables are used as inputs to the WetSpa model. The results of the hydrological simulations show that streamflow in the Vermilion basin may decrease substantially, especially in summer as a result of less precipitation but mainly due to increased evapotranspiration. Predictions also indicate that reduced precipitation in summer combined with a substantial increase in evaporative demand may lead to soil moisture deficits in the fall, which could have a negative impact on the natural vegetation and rainfed crop growth.

Select this Article		Quantitative Assessment of Climate Change Impacts on the Hydrology of the North Platte River Watershed, Wyoming Anil Acharya, Thomas C. Piechota, and Glenn Tootle Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000543 Posted ahead of print 17 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract The impact of climate change on water resources is a major issue for regions in the world. Climate parameters such as temperature and precipitation are expected to change in the future and could significantly impact available water resources. This paper assesses long term water availability over the North Platte River watershed, Wyoming, by utilizing the variable infiltration capacity (VIC) hydrologic model and developing streamflow projections under anthropogenic climate change conditions. Uncertainties in the scenarios of climate change and global climate models are assessed by utilizing ensemble multi‐models and multi‐scenarios from the World Climate Research Programme's database. The simulated streamflows are compared using an inter‐model inter‐scenario approach. Based on streamflow projections, there is a possibility of increased annual streamflow for this region through 2100, with maximum streamflow during 2085–2090. The simulated annual streamflows for future periods vary from ‐20% to 62% with respect to the baseline period (1971–2000). In the simulations, the wet months are getting wetter, while the summer months are found to become dryer. The streamflow projections and the range of streamflow can be utilized by decision makers in future water supply and demand management study.

Select this Article		Storm Centering Approach for Flood Predicions from Large Watersheds James C. Y. Guo Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000540 Posted ahead of print 2 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract Most stormwater numerical models assume that the entire watershed area is under the design storm and shall be considered as the tributary area to the design point. Care must be taken when simulating storm runoff generation from a large watershed because the rain storm may only cover a portion of the watershed. Since the area‐averaged rainfall depth decays with respect to the storm‐cover area, the experience of the larger the watershed, the h“igher the flood flow” is no longer true. In this study, a storm centering technique is developed to identify the conservative size of storm cell so that the design runoff rate and volume can be maximized among various locations of storm center. Without any stormwater detention in the watershed, the product of tributary area and area‐weighted rainfall depth serves as the indicator of runoff accumulation through the waterway. When taking detention basins into consideration, the effect of flow attenuation is converted into an equivalent tributary area that is used to maximize the runoff volume at the design point. This maximization procedure has been tested by the Lower Detention Basin designed and built in the City of Las Vegas, Nevada. The method is simple, but sensitive enough to identify the critical storm size for conservative designs.

Select this Article		Estimation of Daily Actual Evapotranspiration from ETM+ and MODIS Data over the Head Water of West Liaohe Basin in the Semi‐Arid Regions of China Xiaoli Yang, Liliang Ren, Donglai Jiao, Bin Yong, Shanhu Jiang, and Shaohua Song Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000537 Posted ahead of print 2 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract Evapotranspiration (ET) is an important but unmeasurable component of the hydrological cycle in semi‐arid regions. Traditionally, actual ET is computed as residual in water balance equations. It is derived from estimates of potential ET or, indirectly, from field measurements at meteorological stations. Recently, researchers have begun using scintillometers, remote sensing data, and hydrological models to estimate areal actual ET. In this study, the Surface Energy Balance Algorithm for Land (SEBAL) was used to derive ET maps from Moderate Resolution Imaging Spectroradiometer (MODIS) images over the Laohahe basin and Shalamulun River basin. Impact of ground parameters on ET of the study area was quantified using the spatial analysis techniques of ArcGIS. At the end, ET estimated from Landsat 7 Enhanced Thematic Mapper Plus (ETM+) was compared with that from MODIS data over Shalamulun River basin. SEBAL is a suitable algorithm for mapping evaporation over semi‐arid areas, using MODIS and Landsat images with few or no ground measurement. The ET of the study changes from 0 to 6.57 mm/day. The land use types, elevation, Land Surface Temperature (LST), and terrain all have a direct effect on the spatial distribution of ET. ET simulated from both MODIS and Landsat data give reasonable values with results from Landsat ETM+ is better compare to that of MODIS due to different spatial resolution, which Landsat data has a higher spatial resolution than MODIS.

Select this Article		Role of Climate Variability in Modulating the Surface Water and Groundwater Interaction over the Southeast United States Naser Almanaseer and A. Sankarasubramanian Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000536 Posted ahead of print 2 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract We investigate the role of climatic variability on interannual groundwater and streamflow variability in the Southeast U.S. For this purpose, streamflow and associated groundwater levels are analyzed for 20 basins that are minimally affected by reservoirs and groundwater pumping. Using the spatially‐averaged monthly precipitation time series obtained from the Precipitation Regressions on Independent Slope Model (PRISM), we identify the recharge and discharge periods that influence the groundwater levels during the winter (January‐February‐March, JFM) and summer (July‐August‐September, JAS) seasons. Recharge‐discharge dependency analyses indicate that precipitation during the previous three months influences the groundwater level in a given month. Streamflow in any given month depends on the groundwater level during the previous three months. Principal component analysis (PCA) on the precipitation, temperature, streamflow and groundwater data indicate that groundwater levels and streamflow are the two dominant variables influencing the basin hydroclimatology. Further, relating the percentage variance explained from the PCA to baseflow index (BFI) clearly shows that basins with high BFI have higher eigenvalues, indicating that groundwater is a spatial integrator of hydroclimatic processes. Relating the groundwater levels with El Nino Southern Oscillation (ENSO) index, Nino3.4, shows that interannual variability in JFM groundwater levels could be partially explained by the ENSO conditions, but the relation between JAS groundwater levels and JAS Nino3.4 is not statistically significant. Precipitation forecasts from ECHAM4.5 General Circulation Model indicate that it is possible to quantify groundwater availability during the winter season based on the forecasted precipitation and ENSO conditions.

Select this Article		Estimation of Daily Suspended Sediment Load by Using Wavelet Conjunction Models Jalal Shiri and Özgur Kişi Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000535 Posted ahead of print 29 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract Accurate estimation of sediment loads is important for management and construction of water resources projects. In the first part of the study, the convenient Gene Expression Programming (GEP), neuro‐fuzzy (NF) and artificial neural network (ANN) techniques were applied to estimate suspended sediment loads by using recorded daily river discharge and sediment load data. These models were compared with each other in terms of the coefficient of determination, root mean square error, mean absolute error, variance accounted for and Nash‐Sutcliffe statistic criteria. It was found that the GEP model performed better than the NF and ANN models. In the second part of the study, the discrete wavelet conjunction models with convenient GEP, NF and ANN techniques were constructed and compared with each other. Comparison results indicated that the wavelet conjunction models significantly increased accuracy of single GEP, NF and ANN models in suspended sediment estimation. The wavelet‐GEP model performed better than the wavelet‐NF and wavelet‐ANN models.

Select this Article		The Impact of Stormwater Recharge Practices on Boston Groundwater Elevations Brian F. Thomas, S. M. ASCE and Richard M. Vogel, M. ASCE Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000534 Posted ahead of print 29 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract Over the past century, the City of Boston, Massachusetts, has periodically experienced a decline in groundwater elevations and the associated deterioration of untreated wood piles which support building foundations. To combat declining water tables, Boston enacted a groundwater conservation overlay district enforced by City zoning boards to require stormwater recharge practices for any activity that triggers the zoning bylaw. In Boston, recharge to the water table results from the infiltration of rainfall and snowmelt, leakage from water mains, and recharge from man‐made systems. Increased mitigation activities to reduce unaccounted‐for water have reduced leakage from water mains in the city. Given the high percentage of impervious cover in Boston, the remaining sources of recharge are primarily man‐made systems, including pump and infiltrate systems and stormwater recharge BMPs. The primary objective of this research was to exploit existing information on groundwater elevations and recharge practices to quantify the impact of the required recharge best management practices (BMPs) on the behavior of groundwater elevations in the Back Bay region of Boston. Regional multivariate regression models were developed to determine the potential effects of recharge BMPs on observed groundwater elevations. Our literature review revealed several analogous multivariate linear regression studies, but none which focused on behavior of stormwater BMPs. Our model reveals that the installation of recharge BMPs has a small but highly statistically significant positive impact on groundwater elevations in the Back Bay with the effect being proportional to their capacity and inversely proportional to their distance from the location of interest. The resulting model can be used to predict the impact on average groundwater elevations at a particular location resulting from the installation of a recharge BMP (or a set of such BMPs) of a particular capacity at a particular distance from the location of interest.

Select this Article		Use of Gene Expression Programing for Multi‐Model Combination of Rainfall‐Runoff Models Achela K. Fernando, Asaad Y. Shamseldin, and Robert J. Abrahart Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000533 Posted ahead of print 29 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract This paper deals with the application of an innovative method for combining estimated outputs from a number of rainfall‐runoff models using Gene Expression Programming (GEP) to perform symbolic regression. The GEP multi‐model combination method uses the synchronous simulated river flows from four conventional rainfall‐runoff models to produce a set of combined river flow estimates for four different catchments. The four selected models for the multi‐model combinations are the Linear Perturbation Model (LPM), the Linearly Varying Gain Factor Model (LVGFM), the Soil Moisture Accounting and Routing (SMAR) Model, and the Probability‐Distributed Interacting Storage Capacity (PDISC) model. The first two of these models are ‘black‐box’ models, the LPM exploiting seasonality and the LVGFM employing a storage‐based coefficient of runoff. The remaining two are conceptual models. The data of four catchments with different geographical location, hydrological and climatic conditions, are used to test the performance of the GEP combination method. The results of the model using GEP method are compared against original forecasts obtained from the individual models that contributed to the development of the combined model by means of a few global statistics. The findings show that a GEP approach can successfully used as a multi‐model combination method. In addition, the GEP combination method also has benefit over other hitherto tested approaches such as an artificial neural network combination method in that its formulation is transparent, can be expressed as a simple mathematical function, and therefore is useable by people who are unfamiliar with such advanced techniques. The GEP combination method is able to combine model outcomes from less accurate individual models and produce a superior river flow forecast.

Select this Article		Drought Analysis under Climate Change Using Copula Shahrbanou Madadgar and Hamid Moradkhani Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000532 Posted ahead of print 29 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract The joint behavior of drought characteristics under climate change is evaluated using copula method which has recently attained popularity in analysis of complex hydrologic systems with correlated variables. Trivariate copulas are applied, in this study, to analyze the major drought variables, including duration, severity, and intensity, in Oregon's Upper Klamath River basin. Results show that, among the variables, duration‐severity exhibits the strongest correlation whereas duration‐intensity exhibits the least correlation. The impact of climate change on future droughts is evaluated using five General Circulation Models (GCMs) under one emission scenario. Despite more intense extreme events are expected to occur in most parts of the globe in the future, the results of this study show that the Upper Klamath River basin in the Pacific Northwest will experience less intense droughts affected by climate change. Compared to historical events, an overall decrease in drought duration and severity is estimated for this study area in the time period of 2020 to 2090 with maximum drought duration shown to decline from 8 months to 5 months. Among the five GCMs employed in this study, GFDL‐CM2.1 and CSIRO‐MK3.0 are identified as the wettest and driest projections, respectively. High uncertainty associated with GCM products is demonstrated in the analysis of return period by means of bivariate copulas. However, all projections result in larger return periods (i.e., less frequent droughts) compared to historical droughts during the reference period.

Select this Article		The Vegetated Roof Water Balance Model: Experimental and Model Results James A. Sherrard, Jr. and Jennifer M. Jacobs Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000531 Posted ahead of print 24 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract A five parameter, daily vegetated roof water balance model (VR‐WBM) was developed, calibrated, and validated using experiment vegetated roof data from the Seacoast New Hampshire region. The lysimeter experiment on a sedum canopy characterized water storage with a 0.051 mm resolution. Overall, the results show that the average stormwater runoff reduction was 32% for the study period and an average reduction per storm of 57%. Average daily ET rates were 1.24 mm/day during the warmest month and 0.52 mm/day during the coolest month. For well‐watered conditions, the ET losses were well modeled using a grass reference ET value with a crop coefficient of 0.53 for the study's sedum canopy where the onset of stomatal closure occurs when the soil moisture is 0.11 m³/m³. When soil moisture content values are lower than 0.11 m³/m³, evapotranspiration rates decrease linearly with declining soil wetness. The VR‐WBM does an excellent job predicting runoff (R² = 0.98) and storage (R² = 0.94). While ET had a lower R² value (R² = 0.59), the average ET values were within 3% of the observed values and they do not appear to impact storage and runoff predictions. Additionally, the model demonstrated an ability to accurately quantify antecedent soil moisture and its impact on runoff generation.

Select this Article		The Hydrologic Response of Solar Farms Lauren M. Cook and Richard H. McCuen Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000530 Posted ahead of print 24 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract Because of the benefits of solar energy, the number of solar farms is increasing; however, their hydrologic impacts have not been studied. The goal here was to determine the hydrologic effects of solar farms and examine whether or not stormwater management is needed to control runoff volumes and rates. A model of a solar farm was used to simulate runoff for two conditions: the pre‐ and post‐paneled conditions. Using sensitivity analyses, modeling showed that the solar panels themselves did not have a significant effect on the runoff volumes, peaks, or times to peak. However, if the ground cover under the panels is gravel or bare ground, due to design decisions or lack of maintenance, the peak discharge may increase significantly, with stormwater management needed. In addition, the kinetic energy of the flow that drains from the panels was found to be greater than that of the rainfall, which could cause erosion at the base of the panels. Thus, it is recommended that the grass beneath the panels be well maintained or that a buffer strip be placed after the most down gradient row of panels. This study, along with design recommendations, can be used as a guide for the future design of solar farms.

Select this Article		Evolution of the SCS Runoff Curve Number Method and Its Application to Continuous Runoff Simulation J. R. Williams, N. Kannan, C. Santhi, X. Wang, and J. G. Arnold Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000529 Posted ahead of print 24 October 2011 Full Text: \| Download PDF See Also: Erratum
	+ -	Show Abstract The Natural Resources Conservation Service (NRCS) (previously Soil Conservation Service (SCS)) developed the SCS runoff curve number (CN) method (Mockus, 1949) (U.S. Department of Agriculture, Soil Conservation Service 1972) for estimating direct runoff from storm rainfall. The NRCS uses the CN method for designing structures and for evaluating their effectiveness. Structural design is usually based on a single event of a certain probability of occurrence. During the years when many flood water retarding watershed projects were planned and constructed (1950–1980) the CN equation was used in a continuous mode to evaluate the projects. To operate CN in a continuous mode runoff was estimated from a daily rainfall record of about 30 years. For each day of recorded rainfall the five day antecedent rainfall was used to assign a CN₁ (dry condition), CN₂ (average condition), or a CN₃ (wet condition) and runoff was estimated with the appropriate CN. With the development of continuous hydrologic simulation models CN was related directly to soil water content or estimated using rainfall and potential evapotranspiration (PET) to drive an index. Several methods were attempted and used with different degrees of success over a period of many years. The purpose here is to describe the evolution of the continuous CN method and recent developments. Test results based on the direct link soil moisture approach and the revised soil moisture index method are presented for demonstration purposes. Results indicate that the revised soil moisture index method is robust and produces realistic runoff estimates over a wide range in soil properties.

Select this Article		Prediction of Sediment Concentration in Rivers by Recursive Least Squares and Linear Minimum Variance Estimators Kazumasa Mizumura Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000528 Posted ahead of print 24 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract Peaks of suspended sediment concentration in rivers appear before peak discharge appears. The observation of discharge is usually done in many rivers for river management, but the suspended sediment concentration is not always observed. The suspended sediment concentration is expressed by a sediment‐rating curve over a long period of time. But coefficients in the sediment‐rating curve are time‐varying. The time variation of the suspended sediment concentration is predicted by the sediment‐rating curve with the recursive least squares and the linear minimum variance estimators. Since the sediment‐rating curve is linearized by the logarithmic transformation, we can apply the simple linear models such as recursive least squares and linear minimum variance estimators for the prediction of the suspended sediment concentration. These methods indicate that the coefficients in the sediment‐rating curve are time‐varying. These methods can estimate sediment discharge by identifying the coefficients in the sediment‐rating curve. Nash‐Sutcliffe model efficiency coefficients indicate that the three‐day ahead prediction is possible with accuracy. The recursive linear minimum variance estimator is compared with the recursive least squares estimator. As a result, the recursive linear minimum variance estimator is not always better than the recursive least squares estimator, although the former is theoretically superior to the latter as long as the assumption of the linear minimum variance estimator holds. The application of these methods to the prediction of the suspended sediment concentration is found to be possible, because discharges are assumed to be observed in many rivers everyday.

Select this Article		The Study of the Xinanjiang Model Parameter Calibration Li Zhijia, Xin Penglei, and Tang Jiahui Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000527 Posted ahead of print 24 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract The Xinanjiang model parameter calibration is an optimization problem which aims to determine the values of model parameters that provide the best fit between observed and estimated flows. Many researchers have used the Shuffled Complex Evolution (SCE‐UA) algorithm in the Xinanjiang model parameter calibration and have found some problems in its application. Identifying methods in choosing an objective function, the amount of calibration data to be used, and the best calibration steps in searching for the best parameters are just some of the application problems that must be solved. The goal of the present study is to resolve the aforementioned problems. This work calibrates the Xinanjiang model for the Yuetan Basin based on the SCE‐UA method. In the objective function study, six objective functions are commonly used. Results demonstrate that the Water Quantity Balance Error function is the best choice in both daily and hourly Xinanjiang model calibrations. During the experiment, 20 sets of observed data with length differences of 1–20 years are used. Results reveal that data amounting to a period of 16 years are needed to obtain a relatively stable parameter set. Meanwhile, the objective optimization method is introduced in the calibration steps study. This method combines the coupling of the objective optimization method with the SCE‐UA algorithm. Parameter calibration results reveal that the combined method can increase the calibration speed and reduce the influence of the calibration data period on the results.

Select this Article		Estimation Procedures for the General Extreme Value Distribution for the Maxima: An Alternate PWM Method Jose A. Raynal‐Villasenor Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000525 Posted ahead of print 24 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract The moments (MOM1 and MOM2), maximum likelihood (ML), sextiles (SEX1 and SEX2) and probability weighted moments (PWM1 and PWM2) methods for estimating the parameters and quantiles of the general extreme value (GEV) distribution for the maxima were analyzed and compared by using data generation techniques of the type of distribution sampling experiments. Considering variance, bias, and mean square error criteria of estimates of parameters and quantiles, it is concluded that in general for the sample sizes analyzed 9 ≤ N ≤ 99 and non‐exceedance probabilities in the range 0.90 ≤ F ≤ 0.99, the ML method is superior to the other six. However, the simpler methods may be as good depending on the sample size. The PWM2 is a good option to estimate the location and shape parameter, while MOM1 and MOM2 are an alternative when estimating the shape parameter. Thus, for estimating quantiles for N ≤ 19 the MOM1, MOM2 and PWM2 method compares quite well with the ML method, while for N >19 the PWM2 shows a better performance. When compared with ML, the PWM2 method showed an overall better performance in estimating the quantiles for large negative values of the shape parameter and for small sample sizes.

Select this Article		Parameter Estimation and Vulnerability Assessment of Coastal Unconfined Aquifer to Saltwater Intrusion: A Case Study A. Mahesha, K. Vyshali, U. A. Lathashri, and H. Ramesh Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000524 Posted ahead of print 24 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract The focus of the present work is to characterize a tropical, coastal aquifer and to carry out it's vulnerability to saltwater intrusion using hydro‐geological parameters. The characterization of the aquifer involves pumping tests, vertical electrical sounding and water quality analysis carried out at 41 monitoring wells. The area under investigation lies between two tropical, seasonal, tidal rivers ie. Pavanje and Gurpur rivers, joining the Arabian sea in the west coast of India. The aquifer is predominantly a shallow, unconfined aquifer having moderate to good groundwater potential with transimissivity and specific yield ranging from 49.2m²/day to 461.4m²/day and 0.00058 to 0.2805 respectively. The electrical resistivity tests indicated that the thickness of the aquifer ranges from 18m to 30m. The study also investigates on the saltwater affected areas in the region from the vertical electrical sounding and water quality analysis. The resistivity results revealed several probable isolated saltwater intruded pockets in the region with resistivity less than 70 ohm‐m. From the salinity analysis of water, the locations which are affected only during February to May (summer) and throughout the year are identified. The wells which are located very close to the coast (<350m) and at lower elevations (well bottom < +1m) were found to be saline throughout the year. Also, wells along the banks of the river show considerable salinity (>200ppm) during the summer period due to tidal inflow along the rivers. The water samples were also analyzed for chloride to bicarbonate ratios during December to May at all the monitoring wells and were found to be exceeding the allowable limit at several locations. The saltwater vulnerability maps are derived for the area by the GALDIT method using the hydro‐geological parameters. The method was found to be quite effective while comparing with the field observations. The results from GALDIT analysis indicate that the aquifer is medium to highly vulnerable to saltwater intrusion at majority of the locations. The impact of projected sea level rise by 0.25m and 0.50m due to the climate change is also assessed on the vulnerability of the region to saltwater intrusion.

Select this Article		Identification of Aquifer Parameters from Pumping Test Data with Regard for Uncertainty Nicholas Dudley Ward and Colin Fox Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000521 Posted ahead of print 6 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract When fitting hydraulic models of groundwater flow to pumping test data, Bayesian inference provides a framework for quantifying the posterior uncertainty of aquifer parameters estimated from data, and the most likely range of parameters that are consistent with the data. In this study we assume that we measure noise‐perturbed drawdown data. For clarity, we consider groundwater models with few parameters and use Markov Chain Monte Carlo to quantify uncertainty of transmissivity, storativity and leakage parameters. These models exhibit many of the features typically encountered in much higher dimensional computational groundwater models like multi‐modality, failure of least squares algorithms, and poorly determined parameters. For comparison we contrast Bayesian inference with least squares model fitting.

Select this Article		Numerical Simulation of Groundwater Table Falling In Horizontal and Sloping Aquifers by Differential Quadrature Method (DQM) A. Ghaheri and S.H. Meraji Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000516 Posted ahead of print 6 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract Since a nonlinear partial differential equation was developed by Boussinesq on the basis of Darcy's law and Dupuit‐Forchheimer assumption, it has played an essential role in the development of simulation models for solution of various flow problems in porous media. To solve Boussinesq equation, both analytical and numerical solutions such as Finite Difference (FD) or Finite Element (FE) have been sought. Differential Quadrature Method (DQM) is a new numerical method frequently used by researchers to solve partial differential equations. In this paper, DQM have been coupled with explicit, implicit and Crank‐Nicholson FD and applied to solve Boussinesq equation for a drainage problem. This case has been solved previously both analytically and numerically including DQM by other researchers. Those who had employed DQM, had linearized Boussinesq equation first and solved the linearized form implicitly. In this work, nonlinear form of Boussinesq equation has been solved using three models based on DQM for solving dimensionless form and one approach for dimensional form of Boussinesq equation. The obtained results and their degree of accuracy are compared with available experimental and numerical data found in the literature and on that basis, it is concluded that DQM generates accurate results, is very easy to formulate and operate, does not need large mesh size, and is very time efficient.

Select this Article		Spatial Mapping of Runoff from a Watershed Using SCS ‐ CN Method, Remote Sensing and GIS N. Nagarajan and S. Poongothai Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000520 Posted ahead of print 30 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract This study aims to simulate the runoff depth using SCS‐CN method with Remote Sensing and Geographical Information System. In this study, SCS Curve Number technique adapted for Indian condition has been used for generation of CN for an ungauged watershed. The USDA SCS‐CN method is used for estimating the runoff depth in Manimuktha sub‐watershed. Monthly and Annual runoff values have been obtained from the daily runoff values of the watershed. Base map, Soil map and Land use map of the study area have been prepared using Remote Sensing data and Survey of India (SOI) toposheets. The vector layers have been generated in Arc/Info GIS 9.1 software. The SCS model is then applied to estimate the daily runoff from the watershed and validated comparing it with the observed runoff of few selected events of monsoon periods of 1980 – 2009. The statistical analysis indicates that the SCS — CN method can be applied to predict runoff depths of ungagued watershed. The present study reveals that Remote Sensing and GIS based SCS‐CN model can be used effectively to estimate the runoff from the ungauged Indian watersheds of similar geo‐hydrological characteristics.

Select this Article		Long‐Term Water Level Forecasting and Real‐Time Correction Models in the Tidal Reach of the Yangtze River Guofang Li, Xinyi Xiang, Jie Wu, and Ya Tan Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000519 Posted ahead of print 28 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract In this research, considering the importance and complexity of the water level forecast in tidal reach, case study was done in the tidal reach of the Yangtze River. Through the analysis of the characteristics of water level variations, tidal harmonic analysis was introduced into tidal reach, which was commonly applied in oceanic water‐level forecast. Automatic partial tide selection and optimization pattern was used to calibrate harmonic constants, long‐term water level forecast models were developed for Yanglin, Xuliujing, Tianshenggang and Jiangyin stage stations. And then the long‐term forecast models were used to hindcast historical water level events at the abovementioned stations. It was found that most of the results were with high accuracy. There were also some occasional significant errors, which could be attributed to the effects of upstream runoff and downstream storm surge. Based on these findings, response functions of water‐level forecast error to the variation of upstream runoff and the variation of storm surge were developed, which were used in the real‐time correction of the simulation results obtained from long‐term forecast model. The forecast accuracy was improved evidently. These models have already been used in water level forecast in the tidal reach of the Yangtze River for the construction of two large bridges, which also has the potential to contribute to water level forecast in similar tidal reaches of other rivers.

Select this Article		Steady Subsurface Drainage of Ponded Surface by an Array of Parallel Ditches Bhagu R. Chahar and Ghanshyam P. Vadodaria Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000518 Posted ahead of print 28 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract An array of ditches method of subsurface drainage is advantageous for various playgrounds, golf courses, parks and also for orchard plantation where there is little farming operations. A comprehensive analytical solution for the problem of subsurface drainage of a ponded surface by an array of parallel ditches has been obtained by conformal mapping. The symmetry about the vertical axis has been considered in obtaining the solution for half of the drainage domain. The presented solution is applicable for the two dimensional steady drainage from a horizontal ponded surface of finite depth to an array of parallel ditches in homogeneous and isotropic porous medium having an impervious layer lying at finite depth or at infinite depth. The solution includes equations for the quantity of drainage from the seepage face part as well as the water depth part of the ditch. The solution also comprises expressions for the variation in seepage velocity at various locations along the porous medium. Further, particular solutions (e.g. single ditch, empty ditch, ditch of negligible width, impervious layer at infinite depth or at the bottom of ditch) have been deduced from the proposed generalised solution. The single ditch solutions have been verified with the existing results of Youngs.

Select this Article		Analyzing Indiana Reservoirs Inflow Trend Using Self‐Organizing Map Alfie Ningyu Song, V Chandramouli, and Nimisha Gupta Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000517 Posted ahead of print 28 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract Inflows to reservoir systems are affected by climatic changes. In the past, regional inflow trend analyses were conducted using statistical approaches. This research made use of an artificial intelligence technique called Self Organizing Map (SOM) to perform trend and cluster analysis for the inflows into the flood control reservoirs of Indiana. Along with SOM, this research also used the Mann‐Kendall test and a revised Mann‐Kendall test for regional analysis. Results indicate an increasing trend in the clusters which represent days with high inflows to the northern reservoirs of Indiana when inflows to the central and southern reservoirs were low or medium. A 7% increase was noticed in the annual daily counts belonging to this cluster during the past 20 years. Similar trends were observed concerning high inflow days to the central reservoirs of Indiana. However, they are not statistically significant at a 95% confidence level. This study concludes that SOM is a useful tool for studying the trends at a regional level.

Select this Article		Forecast Modeling of Monthly Runoff with Adaptive Neural Fuzzy Inference System and Wavelet Analysis Li Ren, Xin‐Yi Xiang, and Jian‐Jun Ni Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000514 Posted ahead of print 28 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract There is no real periodicity in the change of hydrological system. Changes in hydrological system take place with different periodic variations from time to time. In this paper, a new prediction method for monthly runoff with wavelet analysis technique was utilized. Taking advantage of localized characteristics of wavelet transform and approximation function of Adaptive Neural Fuzzy Inference System (ANFIS), the combined approach of wavelet transform and ANFIS model was used for monthly runoff prediction. The ANFIS forecast model for monthly runoff based on wavelet analysis was established. To solve the problems related with large amplitude of intra‐and inter‐annual variation of monthly runoffs, resolving and reconstructing technique of wavelet was utilized to decompose runoff series into different information subspace, by which decomposition signals with different frequencies were obtained. Based on the evaluation of simulated values and measured values in Yichang station, it was found the percent of pass of relative error was 100% and the effect of prediction was acceptable. The certainty factor d_y was 0.91 and the prediction level was A. By comparing the measured values and predicted values, it was found that with this model, the trend of originals could be forecasted, but improvements were still needed. Because the new model is sensitive to the sudden changes of rainfall, together with the irregular monthly runoff variation, it is difficult to forecast the runoff with this model, which should be improved in the future.

Select this Article		Assessing Climate Change Impacts on Precipitation and Flood Damage in Wisconsin Zachary T. Schuster, Kenneth W. Potter, and David S. Liebl Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000513 Posted ahead of print 28 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract Studies on the impacts of anthropogenic climate change have found that the magnitude and frequency of intense precipitation events are expected to increase over the next century for the Midwestern United States. The goal of this study was to use statistically‐downscaled and de‐biased precipitation projections for the state of Wisconsin derived from 14 General Circulation Models (GCMs) to assess the projected precipitation changes for the mid‐21^st century in a way that is relevant to water resource decision‐making. We analyzed metrics that are relevant to stormwater design such as the 100‐year, 24‐hour quantile, and we also evaluated the changes in a risk assessment context using idealized damage functions that translate precipitation depths into economic damages. The results of our design‐metric analysis shows that the 100‐year, 24‐hour quantiles for Wisconsin are projected to have significant but modest increases of about 11% over the next 50 years. Our risk assessment shows that the largest percent changes in risk for Wisconsin are projected to be in the northeast portion of the state. Both of these analyses will be used as part of the Wisconsin Initiative on Climate Change Impacts (WICCI) to develop climate change adaptation strategies for communities throughout the state.

Select this Article		Field Test on Conversion of Natural Watershed into Kinematic Wave Rectangular Plane James C. Y. Guo, Jeff C. Y. Cheng, and Len Wright Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000512 Posted ahead of print 28 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract Conversion of a natural watershed into its equivalent kinematic wave rectangular plane has long been a concern in the practice of stormwater numerical simulations. Based on the principles of mass and energy, the actual watershed and its virtual kinematic wave plane can be related by the watershed shape factor that involves the waterway length and slope, and watershed area. In this study, two dimensionless watershed shape functions are derived to use parabolic function and trigonometric Sine curve for watershed conversion. These two watershed shape functions produce good agreements with the maximum overland flow length method for hypothetical square watersheds. Also, these two watershed shape functions are able to re‐produce similar kinematic wave plane widths as reported in a calibrated model. Furthermore, in this study, these two watershed shape functions are tested by nine observed rainfall events and three levels of modeling details. These 54 case studies reveal that the parabolic shape function consistently produces better agreements with the observed runoff hydrographs. Also, it is concluded that a model with more drainage details results in higher peak flows. On the contrary, a model with a low resolution tends to decrease the peak flow because of the significant surface detention volume spread in the overland flow.

Select this Article		Analytical Solution of Nonlinear Diffusion Wave Model Kazumasa Mizumura Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000511 Posted ahead of print 21 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract The governing equations of the open channel flow are the Saint Venant equations when a flood propagates. To obtain an analytical solution of the Saint Venant equations, they are approximately transformed to a nonlinear diffusion equation. The numerical result of the analytical solution of the nonlinear diffusion equation explains the nonlinearity of the open channel flow and the overland flow and the resulting asymmetry of the water surface profile. When we numerically apply the Saint Venant equations for flood routing in a finite region and finite time, a downstream boundary condition is necessary. The analytical solution of the appropriate nonlinear diffusion equation does not require the downstream boundary condition. The numerical result of the analytical solution of the approximate nonlinear diffusion equation is found to be suitable to simulate the original nonlinear differential equation and the Saint Venant equations. The linearized diffusion model is found to be restricted in practical applications and it cannot express the nonlinearity. The attenuation of flood peak is also approximately derived and compared with numerical computation for the analytical solution of the approximate nonlinear diffusion equation, the nonlinear diffusion equation, the Saint Venant equations, and the linearized diffusion equation.

Select this Article		Differential Quadrature Method in Open Channel Flows: Aksu River, Turkey Birol Kaya, Aslı Ulke, and Cevza Melek Kazezyılmaz‐Alhan Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000509 Posted ahead of print 15 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract Diffusion wave equation, which is derived from the Saint‐Venant equations for one‐dimensional, gradually varied, unsteady open‐channel flow, describes the wave propagation in open channels. Therefore, it is important to solve the diffusion wave equation accurately and efficiently. In this paper, a numerical solution for diffusion wave equation is developed by using the Differential Quadrature Method (DQM). The performance of DQM is tested against two other numerical solution methods which are the finite difference method (FDM) and finite volume method (FVM). In order to demonstrate the applicability of DQM, first a hypothetical example is solved with both DQM and two other numerical methods. Then, the DQM is applied to a real flooding event occurred in Aksu River, Sutculer Basin located in Mediterranean Region, Turkey. The measured flow rates are routed through the Aksu River by diffusion wave equation and the outflow is obtained by DQM. Finally, this flood event is also solved by explicit and implicit approximations of FDM and FVM and the results are compared to the solution obtained by using DQM. Based on the comparison of the results, it is concluded that DQM provides close results to FDM and FVM but with higher computational speed, less nodes and memory usage.

Select this Article		A Dynamic Sub‐Timing Based Implicit Non‐Oscillating Scheme for Contaminant Transport Modeling Chaitali Misra, S. T. Manikandan, S. Murty Bhallamudi, and Sorab Panday Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000507 Posted ahead of print 15 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract A dynamic sub‐time stepping method is described for solving contaminant transport problems that utilize higher order implicit time marching procedures with higher accuracy non‐oscillating spatial discretization methods to resolve sharp plume fronts in advection dominated systems. Non‐oscillating spatial discretization methods for the advective term prevent unphysical oscillations and minimize numerical diffusion. Second order temporal accuracy is achieved by using the Crank‐Nicholson implicit scheme, however non‐oscillating properties may be violated for Courant Numbers larger than one, leading to spurious oscillations. The proposed sub‐timing method allows use of small time‐step sizes in critical portions of a domain, with larger time‐step sizes in other locations. This locally limits the Courant number where required and still keeps the general solution free of time‐step size restrictions. This technique makes it possible to apply higher‐order non‐oscillating schemes with higher‐order temporal weighting for advection dominated flows, even when the Courant number is much greater than one. Feasibility and applicability of the dynamic implicit sub‐timing method are demonstrated through three proof‐of‐the‐concept example problems.

Select this Article		A Hybrid Wavelet—Genetic Programming Approach to Optimize ANN Modelling of Rainfall—Runoff Process Vahid Nourani, Mehdi Komasi, and Mohammad Taghi Alami Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000506 Posted ahead of print 15 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract In this paper, the wavelet analysis was linked to the genetic programming (GP) concept for constructing a hybrid model to detect the seasonality patterns in the rainfall—runoff time process. This approach was used to determine the dominant input variables of artificial neural network (ANN) rainfall—runoff model via a sensitivity analysis. In this way, the main time series of two variables, rainfall and runoff, were decomposed into some multi—frequently time series by the wavelet transform. Then, these decomposed time series were imposed as input data to the GP to optimize the input structure of ANN model. This methodology was utilized in daily and monthly time scales modeling for two watersheds with distinct climatologic regimes. The obtained results were compared favorably to ANN and GP models. The obtained results showed that the proposed model can monitor both short and long term patterns due to the use of multi—scale time series of rainfall and runoff data as the GP inputs. Moreover, using the proposed sensitivity analysis, the number of input variables in the ANN modeling was decreased.

Select this Article		A Soft Computing Based Workable Flood Forecasting Model for Ayeyarwady River Basin of Myanmar Anil Kumar Kar, Lai Lai Winn, A. K. Lohani, and N. K. Goel Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000505 Posted ahead of print 15 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract It is a challenging task for working hydrologists of the Myanmar to get information from all gauge and discharge sites during flood in order to model the forecast properly. In such a case the concept of this work is very useful for the real time flood forecasting particularly when the data of all the gauge sites are not available regularly or timely. In that context one has to rely upon some accessible sites to get a workable forecast. Besides that a best combination of the available data can be selected for making the flood forecast. The study is done for establishment of a flood forecasting model with maximum efficiency using very less information. Three upstream sites named as Sagaing, Monywa and Chauk of Ayeyarwady river are selected as the base station and the downstream Pyay as the forecasting station in this study. The Artificial Neural Network (ANN) multi layered feed forward (MLFF) network along with Takagi‐Sugeno (TS) fuzzy inference model are applied here. The developed model is used to forecast the stage from 1 to 4 days in advance. The values of three performance evaluation criteria namely, the efficiency, the root‐mean‐square error (RMSE) and the coefficient of correlation, were found to be very good and consistent. The results of ANN and fuzzy models are remaining at par but fuzzy model remain somewhat better than ANN model. It is determined that for stage forecasting at Pyay, preferably the stage at Sagaing‐Monywa‐Chauk, Sagaing‐Monywa or Sagaing‐Chauk is necessary on priority basis. Regarding influence of base stations on forecasting, Chauk remains best, then Sagaing and Monywa. The Fuzzy model is performing better than ANN model when the case of peak modeling comes. The study provides a best combination of available data for workable flood forecasting with sufficient lead time for planning and operating the relief measures.

Select this Article		Flood Coincidence Risk Analysis Using Multivariate Copula Functions Lu Chen, Vijay P. Singh, F. ASCE, Guo Shenglian, Zhenchao Hao, and Tianyuan Li Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000504 Posted ahead of print 15 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract The coincidence of flood flows of the mainstream and its tributaries may determine flood peaks. This study analyzed the risk of flooding due to such flood coincidences by considering flood magnitudes and time (dates) of occurrence. The Pearson Type III distribution and Log Pearson Type III were selected as the marginal distribution of flood magnitude for annual maximum flood series and the mixed von Mises distribution as the marginal distribution of flood occurrence dates. Two four‐dimensional copula functions were developed for the joint distribution of flood magnitudes and occurrence dates. The upper Yangtze River in China and Colorado River in U.S. were selected to evaluate the method of computing risk. The coincidence probabilities of flood magnitudes and dates were calculated, and the conditional probabilities for the Three Gorges Reservoir (TGR) were analyzed. Results show that the von Mises distribution can fit the observed flood dates data well. The X‐Gumbel copula was selected for risk analysis. Based on the proposed model, the coincidence and conditional probabilities for any return period were obtained.

Select this Article		The Precipitation Recycling in Tarim River Basin He Hai and Lu Guihua Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000503 Posted ahead of print 15 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract Precipitation recycling plays a key role in hydrological cycle process. The precipitation recycling ratio is a diagnostic measure for interactions between land surface hydrology and regional climate. In order to demonstrate the influence of hydrological cycle on the climate of arid area in north‐west China, we have studied precipitation recycling ratio and the characteristics of hydrological cycle in Tarim River Basin which includes characteristics of water vapor transportation flux divergence and convergence, evaporation and its spatial distribution, and the spatial distribution of precipitation recycling ratio. The results suggest that there is about 14 percent of annual precipitation coming from the evaporation of Tarim River Basin, and 86 percent of advected precipitation coming from the surrounding external areas to the region. It is lower than other world famous river basin such as Amazon, Mississippi, the Yellow River and Yangtze River Basins. The recycling is active over the region during the months from April to July, and extremely inactive during the months from October to next January. The recycling ratio is relatively high in the north‐west and north area where human beings live and open up large tracts of wasteland for cultivation, and then change the land surface which acts as a significant source of moisture to the atmosphere during certain seasons. Analysis of the recycling ratios spatial distribution suggests that the basin's unique topography and land surface use change (through evapotranspiration) act on the precipitation and its recycling over the basin.

Select this Article		Stormwater Runoff and Deep Groundwater Drainage in Two Closed Basins M. Nachabe, F. ASCE, V. Martysevich, and J. Su Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000502 Posted ahead of print 15 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract Closed basins dotting the landscape of South and Central Florida aroused the interest of numerous hydrologists in the past. Lacking surface water drainage features such as creeks and natural streams, closed basins drain internally through the subsurface during storm events. Little is known, however, about the magnitude and role of subsurface drainage fluxes in recharging deep groundwater aquifers. In this study, we deploy instruments to monitor the surficial and deep aquifer heads at groundwater discharge points in two urbanized closed basins. The purpose of the study was to develop and apply field methods to estimate rapid subsurface runoff following rainfall events and to evaluate the effectiveness of internal drainage in urban drainage planning. The two sites were in Hillsborough County Florida, and one location was a 6 meters ‐ deep sinkhole that receives urban runoff from the rest of the basin. The data captured rapid subsurface drainage exceeding 25 cm/day at these discharge locations following rainfall. The two locations collected subsurface runoff rapidly, and released the runoff gradually into the deep aquifer system. Results have practical implications in urban drainage for closed basins.

Select this Article		Estimation of Spatio‐Temporally Variable Groundwater Recharge Using a Rainfall‐Runoff Model M. A. Moreno and B. E. Vieux Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000501 Posted ahead of print 24 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract This paper describes radar‐based estimation of groundwater recharge by means of distributed hydrologic modeling used to estimate components of the hydrologic water balance. Conventional management of water resources has focused on groundwater as a separate constituent of surface water in the hydrologic systems, but factors such as precipitation, surface runoff, baseflow, evapotranspiration, and water demands determine the change in storage in a stream‐aquifer system that varies in both time and space. We have estimated the temporal and spatial variability of groundwater recharge in the eastern outcrop of the Arbuckle‐Simpson aquifer, located in Oklahoma. Distributed maps of precipitation from radar were corrected for bias using rain gauges, and used as input to a distributed hydrologic model. Distributed grids of infiltration were combined with evapotranspiration to extend groundwater recharge estimates from three years, when streamflow records existed, to 13 years using archival radar. The results show that better characterization of precipitation and runoff, achieved with bias‐corrected radar, produces more reliable estimates of runoff and groundwater recharge than those derived from the use of rain gauge data alone.

Select this Article		Simulating Turbidity Removal at a River Bank Filtration Site in India Using SCS‐CN Approach C. S. P. Ojha, M. ASCE Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000498 Posted ahead of print 3 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract Use of SCS‐CN approach is very popular among hydrologists. Despite this, its applications in water quality modeling have been very limited. For the first time, the present work explores the potential of SCS‐CN approach in water quality modeling of River Bank Filtration (RBF) process using a theoretical framework. The approach relates Curve Number with the filtration/kinetic coefficient and the input applied to the system. The approach is tested for its effectiveness using the field data collected at River Bank Filtration site at Haridwar in India. CN is found dependent on travel time between source water and abstraction well in addition to the influent concentration. For very low or very high values of influent concentration, curve number exhibits an asymptotic variation approaching to hundred and zero, respectively. Using the data on source water quality and the travel time, it is possible to compute curve number and subsequently, the filtrate quality at an abstraction well.

Select this Article		Model Performance Sensitivity to Objective Function during Automated Calibrations Misgana K. Muleta, Ph. D., P.E. Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000497 Posted ahead of print 3 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract Previous studies have reported limitations of the efficiency criteria commonly used in hydrology to describe goodness of model simulations. This study examined sensitivity of model performance to the objective function used during automated calibrations. Nine widely used efficiency criteria were evaluated for their effectiveness as objective function, and goodness of the model predictions were examined using thirteen criteria. Two cases (Case I: using observed streamflow data and Case II: using simulated streamflow) were considered to accomplish objectives of the study using a widely used watershed model (SWAT) and good‐quality field data from a well‐monitored experimental watershed. Major findings of the study include: (1) Automated calibration results are sensitive to the objective function group, group that work based on minimization of the absolute deviations (Group I), group that work based on minimization of square of the residuals (Group II) and groups that use log of the observed and simulated streamflow values (Group III), but not to objective functions within the group. 2) Efficiency criteria that belong to Group I were the most effective when used as objective function for accurate simulation of both low flows and high flows. (3) Group I and Group II objective functions complement each other's performance. (4) With regard to the capability to describe goodness of model simulations, efficiency criteria that belong to Group I showed superior robustness. 5) For the study watershed, use of the long‐term inter‐annual calendar day mean as baseline model did not improve capability of an efficiency criterion to describe model performance. (6) Even for ideal conditions where uncertainty in input data and model structure are fully accounted for, identifying the so‐called “global” parameters values through calibration could be daunting as parameter values that were significantly divergent from predetermined values produced model simulations that can be considered near perfect even when judged using multiple efficiency criteria.

Select this Article		Synthesis of Rainfall Characteristics for Predicting the Erosivity Pattern of Wakavali Region in Maharashtra, India Sachin Nandgude, Vipul Shinde, and Dilip Mahale Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000496 Posted ahead of print 18 August 2011 Full Text: \| Download PDF
	+ -	Show Abstract Wakavali region of Maharashtra state in India is characterized by high intensity rainfall over short duration. Precipitation in Wakavali occurs mainly during May to October. Raingauge charts of self recording raingauge stations were used for rainfall characteristics analysis. Intensity of storm was recorded along with depth of individual storm. It was found that the variation in magnitude of total kinetic energy was more due to unit increase in magnitude of rainfall depth than unit increase in rainfall intensity by keeping other variables constant. Values of 30‐min maximum rainfall intensity (I₃₀) were found to be very high reaching up to 140mm/hr. Most of higher value of I₃₀ occurred in June and early July. Rainfall intensity of 8mm/hr was treated as threshold rainfall intensity for Wakavali region above which erosion process begins. There was significant correlation between erosivity indices and rainfall parameters viz. I₃₀ and daily precipitation for the threshold rainfall intensity of 8 mm/hr out of four sets of rainfall intensity. Annual average erosivity index for threshold rainfall intensity 8mm/hr set was found as 13460MJ‐mm/ha‐hr. Probability analysis of Annual and Monthly (one day maximum) rainfall at Wakavali reveals that July has maximum precipitation in single day followed by June, August, September and October. From Precipitation Concentration Index it was found that relative distribution of rainfall was highly influencing parameter.

Select this Article		Application of Bayesian Model Averaging Approach to Multi‐Model Ensemble Hydrologic Forecasting Zhongmin Liang, Dong Wang, Yan Guo, Yu Zhang, and Rong Dai Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000493 Posted ahead of print 18 August 2011 Full Text: \| Download PDF
	+ -	Show Abstract Bayesian Model Averaging (BMA) is a statistical method which can synthesize the advantages of different models or methods. The objective of this research is to explore the use of BMA for forecast combination among several hydrological models. BMA is a statistical scheme that infers posterior distribution of forecasting variables by weighing individual posterior distribution based on their probabilistic likelihood measures, with the better performing predictions receiving higher weights than the worse ones. TOPKAPI model and Xin'anjiang (XAJ) model were applied to the Dongwan basin, Yellow River, China for flood simulating. Observed and simulated discharge time series were transformed into normally distributed variables through the Normal Quantile Transform (NQT). The Gaussian Mixture Model was constructed by weighing the posterior distribution of individual hydrological model in the transformed space. The posterior probability measuring samples belong to each specific hydrological model was treated as the weight. The parameters of Gaussian Mixture Model and weight of each hydrological model were estimated by the Expectation Maximization (EM) Algorithm. Thus, the forecast combination from the two hydrological models was obtained in the catchment. The results provide, for flood forecasting, not only the mean discharge values, but also the quantitative evaluation on forecasting uncertainties (e.g. standard deviation and confidence interval), as the BMA approach could calculate the estimation of the probability distribution of forecasted variables.

Select this Article		Development of an Integrated Adaptive Resonance Theory Mapping Classification System for Supporting Watershed Hydrological Modelling Bing Chen, M. ASCE, Pu Li, S. M. ASCE, and Tahir Husain Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000492 Posted ahead of print 18 August 2011 Full Text: \| Download PDF
	+ -	Show Abstract As it is a critical process of watershed management, classification always faces challenges of inefficiency in handling complexity and uncertainty. This study attempts to fill this gap by developing an integrated adaptive resonance theory mapping system consisting of a two‐stage adaptive resonance theory mapping (TSAM) approach and an integrated rule‐based fuzzy adaptive resonance theory mapping (IRFAM) approach. In order to demonstrate their feasibility and efficiency, TSAM and IRFAM were compared with conventional adaptive resonance theory mapping (ARTMap) in two case studies in the Deer River watershed in Manitoba, Canada, which were classifications of watershed sub‐basins and types of land cover to support hydrological modelling. Among the three approaches, IRFAM performed best in effectively processing the classification for input patterns with a high level of uncertainty and a wide range of variations, although it required pre‐defined criteria. TSAM performed reasonably well by generating criteria for supervised classification based on the internal relationship of the original data, indicating its advantage in handling an insufficient data situation with a low demand for subjective judgment. Consequently, the two developed approaches could be complementary and improve classification efficiency and robustness in dealing with systematic complexity and uncertainty and supporting watershed hydrological modelling.

Select this Article		A Hydrologically‐Enhanced Distributed Urban Drainage Model and Its Application to Beijing City Anjun Pan, Aizhong Hou, Fuqiang Tian, Guangheng Ni, and Heping Hu Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000491 Posted ahead of print 18 August 2011 Full Text: \| Download PDF
	+ -	Show Abstract Heavy rainfall induced inundation is becoming more serious in urban areas which makes it necessary to urgently appraise and redesign the infrastructure system to drain the storm water more efficiently. For the complex urban drainage systems that include street, sewer and ditch/river networks, a sophisticated urban drainage model is required to facilitate optimal planning and management. While most existing models simulate runoff generation process in a simpler manner and treat the drainage connections between runoff generation cells and the corresponding drainage links in a rigid/static manner, this study proposes a new hydrologically‐enhanced distributed urban drainage model. In the new model, the urban area is discretized into four‐layer network, i.e., two dimensional (2D) grid network, 1D street network, 1D sewer network and 1D ditch/river network. Physically based equations are utilized to describe water movement along the four networks, i.e., the 1D Richards equation is used to simulate the infiltration process along the vertical direction in the grid network, the 2D Saint‐Venant equation is used to simulate the overland flow process along the planar direction in the grid network, and the 1D Saint‐Venant equation is used to simulate the street, sewer and river flows in the remaining networks. The new model incorporates the state‐of‐the‐art physical descriptions about hydraulic as well as hydrological processes during urban storm inundation period, which allows more realistic depiction of runoff generation processes, automatic alteration of overland flow routing path, direct and easier usage of gridded radar rainfall data readily available recently, and real‐time hydrodynamic flux exchanges between surface and sewer pipes. The model is validated in a hypothetical application by comparing with the published literature results. Also, a real urban watershed application shows the capacity of the model to provide reasonable predictions of the outlet hydrograph, which indicates its potential for planning and real‐time management of urban drainage systems.

Select this Article		Investigation into the Impacts of Land‐Use Change on Runoff Generation Characteristics in the Upper Huaihe River Basin, China Qiongfang Li, Tao Cai, Meixiu Yu, Guobin Lu, Wei Xie, and Xue Bai Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000489 Posted ahead of print 8 August 2011 Full Text: \| Download PDF
	+ -	Show Abstract Land‐use change has significant impacts on hydrologic processes at the watershed level, thus, quantitative assessment on the impacts of land‐use change is vital for basin environment protection and water resources sustainable development. Owing largely to computer and GIS technology improvements, the distributed hydrological models, which allow describing the temporal variability and spatial distribution of water balance components, offer an effective approach to quantify the land‐use change effects on watershed water quantity. In this study, Soil and Water Assessment Tool (SWAT) model was used to simulate land‐use change effects on water quantity in the upper Huaihe river basin above the Xixian hydrological controlling station with a catchment area of 10,190 km² by the use of three‐phase (1980s, 1990s, 2000s) land‐use maps, soil type map (1:200000), 1980 to 2008 daily time series of rainfall from the upper Huaihe river basin. Within the model, potential evapotranspiration was computed by Penman‐Monteith method coupling with EPIC model (simplified plant growth model). On the basis of the simulated time series of daily runoff, land‐use change effects on spatio‐temporal change patterns of runoff coefficients and runoff modules, and rainfall‐runoff relationship, the sensitivity of rainfall‐runoff relationship to rainfall for different types of land use, and impact of land‐use patterns on rainfall‐runoff relationships were investigated. The results revealed that under the same condition of soil texture and terrain slope the advantage for runoff generation and the sensitivity of rainfall‐runoff relationship to rainfall descended by farmland, paddy field, woodland. With the same rainfall, the advantage for runoff generation ascended by 1990's, 2000's and 1980's land‐use patterns. The outputs could provide important references for soil and water conservation and river health protection in the upper stream of Huaihe river.

Select this Article		Risk Assessment of Regional Water Resources and Forewarning Model at Different Time Scales Jun Zhao, Zhenping Huang, Juliang Jin, Baohong Lu, Xiaomin Zhang, and Yaqian Chen Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000490 Posted ahead of print 8 August 2011 Full Text: \| Download PDF
	+ -	Show Abstract Aiming at making full use of water resources, a risk assessment of regional water resources and forewarning model was studied in this paper. The model is built upon risk indices in the system, proceeding from the whole structure and its component parts at different time scales. In this paper, on the one hand, it mainly takes the long‐term forewarning way to establish the long‐term forewarning model of regional water resources with three levels of prediction, assessment and forewarning. Hydrological model is employed to simulate the further value of an index. Set pair analysis method is adopted to calculate the connection degree of index risk and systematic risk through multivariate connection number, while the weight of single index is determined on the different influences and their respective connection degrees are updated. The comprehensive assessment is made by assessment matrix with connection degree of comprehensive index. The comparison judging method is used to compartmentalize warning degree of water resources on risk assessment comprehensive index with forewarning standards, and then the long‐term local conditions for proposing the planning scheme of water resources. On the other hand, it mainly takes the real‐time forewarning way to establish the real‐time forewarning model of regional water resources which introduces the real‐time correction technique of Kalman Filter based on the long‐term forewarning model, and then the real‐time local conditions for proposing the emergency plan of water resources. The application results show that the proposed model has strong logic superiority and regional adaptability with strict theoretical system, flexible methods, correct and reasonable results and simple implementation, providing a new way for researching on the risk assessment and forewarning of regional water resources.

Select this Article		Impacts of Land‐Use and Climate Changes on Hydrologic Processes in the Qingyi River Watershed, China Yangyang Liu, Xingnan Zhang, Dazhong Xia, Jinsheng You, Yanshu Rong, and Mohamad Bakir Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000485 Posted ahead of print 5 August 2011 Full Text: \| Download PDF
	+ -	Show Abstract The impacts of human‐induced land‐use and climate changes on hydrologic processes have become a great challenge and attracted widespread attention of many researchers. Dramatic changes in land‐use and climate have occurred in the mountainous Qingyi River watershed in southwest China in the last three decades. Variable Infiltration Capacity (VIC), a large‐scale hydrologic model, was used in this study to assess the impacts of land‐use and climate changes on surface runoff, baseflow, streamflow and evapotranspiration (ET) of this watershed. The analysis for this study includes (1) investigation of change in historical land‐use patterns, (2) detection of climate change (precipitation and mean temperature), and (3) simulation and assessment of hydrologic responses to these changes. The Mann—Kendall test was used to identify the long‐term monotonic trends in precipitation and temperature for the period of 1980–2005. The results suggest no significant change in annual precipitation and a significant increase in annual temperature, particularly in February, April, July and September. The analysis to three land‐use maps reveals that the conversions between forest and shrubland/grassland were the predominant land‐use change over the past three decades. Hydrologic simulations show that the influence of climate change on hydrologic processes was stronger than those of land‐use change. Monthly variation of the river flow was mainly attributed to seasonal variation in precipitation. However, ET responded significantly to the land‐use change in several sub‐watersheds where single land‐cover conversion occurred dominantly. The decrease in surface runoff and baseflow caused by climate change was enhanced by changes in land‐use, whereas the reduction in ET was offset by reforestation over the study period. Furthermore, the impact of deforestation or reforestation on hydrologic processes was more significant in the dry season than other seasons. The results from this study can be a useful reference for decision making in land‐use planning and water resource managements in this region.

Select this Article		Validation of SCS Method for Runoff Estimation Bofu Yu Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000484 Posted ahead of print 5 August 2011 Full Text: \| Download PDF
	+ -	Show Abstract The Soil Conservation Service (SCS) method is widely used to estimate runoff from small to medium‐sized watersheds. The most critical assumption of the SCS method is that the ratio of the actual retention to the potential retention is the same as the ratio of actual runoff to potential runoff, but this assumption has not been empirically validated. The paper develops a framework to test this proportionality assumption that underpins the SCS method. Using data on rainfall intensity and storm runoff amount from 210 site‐events from Australia and southeast Asian countries, this paper shows that there is a strong relationship between the maximum retention based on the SCS equation and the product of the effective storm duration and the spatially averaged maximum infiltration rate, and there is empirical support for the proportionality assumption for runoff estimation. Relating the maximum retention to the effective storm duration and maximum infiltration rate provides additional avenues for prediction of storm runoff amount and peak runoff rate, which are the key design parameters for stormwater control and management.

Select this Article		Morphology Evolution of Cuadai Estuary, Mekong River, Southern Vietnam Thanh Letrung, Qiongfang Li, Yu Li, Trung Vukien, and Quyet Nguyenthai Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000483 Posted ahead of print 30 July 2011 Full Text: \| Download PDF
	+ -	Show Abstract Morphology evolution of estuarine systems is a complex phenomenon. The main processes, involving waves, currents, sediment transport and their interaction with the topography changes, are not fully understood yet at different spatial and temporal scales no matter under natural situations or intensified human interventions. The Mekong river delta, one of the most social‐economic important deltas in Vietnam, is enduring a dramatic morphological change with natural and human interventions. For example, the Cuadai estuary, one of the biggest Mekong's estuaries, is undergoing an intricate change of river shore. The highly dynamic variation of the estuary significantly influences the local economy. Basically, there are four classified methods in the research morphology evolution, including theoretical analysis, field investigation, physical modeling and numerical modeling. Each method has its advantages and disadvantages. Previous studies analyzed survey data or employed remote sensing techniques. However, no sufficient and scrupulous investigation has been conducted for the effects of different factors. In this research, an attempt is made to determine the key factors by setting up a numerical model to simulate the morphological change of this estuary with MIKE 21. After calibration with the measured data in 2002 and 2003, it is applied to analyze the erosion/ deposition pattern of this estuary. The key factors are identified, and the influences of the key factors on the morphological evolution are analyzed.

Select this Article		EMD‐KNN Model for Annual Average Rainfall Forecasting Jian Hu, Jun Liu, Yong Liu, and Cheng Gao Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000481 Posted ahead of print 30 July 2011 Full Text: \| Download PDF
	+ -	Show Abstract The prediction of rainfall is the premise of responding to water resources management and flood defense. Hydrological system is complex, rainfall time series as a member of it has characteristics of nonlinear and non‐stationary, so accurate rainfall prediction still a much difficult job at present. The paper proposes a conjunction model named EMD‐KNN for forecasting annual average rainfall. The model is improved by combining two methods, empirical mode decomposition (EMD) and K‐nearest neighbor bootstrap regressive model (K‐NN). It is applied to case studies of forecasting annual average rainfall for Nanjing city and Dahuofang reservoir basin, where Nanjing city is water‐rich area in East China, Dahuofang reservoir basin is water‐deficient area in Northeast China. Three performance evaluation measures results revealed that the EMD‐KNN model reduce the prediction mean absolute error (MAE), mean relative error (MRA) and root‐mean square error (RMSE) with respect to the single K‐NN model by almost 50% respectively, so the suggested model can effectively improve the forecast accuracy of single K‐NN in forecasting the annual average rainfall.

Select this Article		Copula‐Based Flood Frequency Analysis at Ungaged Basin Confluences: A Case Study for Nashville, TN Shih‐Chieh Kao and Ni‐Bin Chang Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000477 Posted ahead of print 20 July 2011 Full Text: \| Download PDF
	+ -	Show Abstract Many cities are located at or near the confluence of streams where availability of water resources may be enhanced to sustain user needs while also posing an increased flooding risk from multiple tributaries. An accurate flood frequency estimator that models the joint flood potential at a basin confluence is needed. Given that long‐term flow observations are often unavailable, estimating flood frequency at ungaged basin confluences proves challenging. Through the use of copulas, this case study demonstrates how an improved flood frequency analysis can be performed for stream confluences at Nashville, TN. The approach involves four major steps including initial data quality control, fitting of marginal distributions of tributary peak flows, construction of a suitable copula dependence structure, and identification of flood frequency at the confluence point based on synthesized peak flows. This case study may help researchers and practitioners develop a better understanding of joint flood frequency with consideration of upstream dam regulation among several contributing watersheds.

Select this Article		Physically‐Based Hydrological Modeling of the 2002 Floods in San Antonio, Texas Hatim O. Sharif, Singaiah Chintalapudi, Almoutaz A. Hassan, Hongjie Xie, and Jon Zeitler Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000475 Posted ahead of print 16 July 2011 Full Text: \| Download PDF
	+ -	Show Abstract The July 2002 floods in South Texas resulted from excessive precipitation caused by a slow moving tropical wave accompanied by an abundance of tropical moisture, which resulted in 12 deaths and nearly $1 billion in damage. South Central Texas is particularly vulnerable to floods due to: (1) proximity to a moist air source (the Gulf of Mexico); (2) the Balcones Escarpment, which concentrates rainfall runoff; (3) a tendency for synoptic scale features to become cut off and stall over the area; and (4) decaying tropical cyclones stalling over the area. This paper examines the hydrology of the July 2002 floods in three urbanized watersheds in the City of San Antonio and Bexar County, TX. The physically‐based, distributed‐parameter Gridded Surface Subsurface Hydrologic Analysis (GSSHA) hydrologic model was used to simulate the flood over the three watersheds. Various flood control features were included in the simulations. The hydrologic model, driven by the Next Generation Radar (NEXRAD) Multi‐sensor Precipitation Estimator (MPE), was able to reasonably simulate runoff in the three watersheds. Differences in the response of the three watersheds were highlighted together with the role of flood‐control hydraulic structures.

Select this Article		A Coupled Hydraulic and Kalman Filter Model for Real Time Correction of Flood Forecast in the Three Gorges Interzone of Yangtze River, China Xiao‐Ling Wu, Xiang Xiao‐Hua, Wang Chuan‐Hai, Chen Xi, Xu Chong‐Yu, and Yu Zhongbo Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000473 Posted ahead of print 1 July 2011 Full Text: \| Download PDF
	+ -	Show Abstract The Three Gorges Project (TGP) along the Yangtze River in China, as one of the biggest hydropower‐complex projects in the world, plays a significant role in the economic development of the area even of the whole nation. An accurate and reliable flood forecast modeling system is of significant importance for flood control, flood warning, and operation of larger reservoirs. Kalman filter coupling with hydrological models or hydraulic models is one of the efficient methods to adjust real‐time flood series for reducing errors from model structure, input data and calibrated parameters. However, the coupling model is time consuming in computation because the state vectors in this kind of Kalman filter including both water stage and discharge are solved simultaneously. In this study, an alternative coupling method was developed, which separates system state equations and measurement equations allowing the water stage and discharge to be computed alternately. The new method was applied for real‐time flood forecasting in the Three Gorges interzone of Yangtze River. The hydraulic model is calibrated and verified against the observed flood stage and discharge before and during Three Gorges Dam construction periods. Study results demonstrate that the new model is efficient in real‐time flood forecasting. A comparative study shows that the newly developed approach outperforms the conventional methods in terms of modeling efficiency, root mean square error, as well as the forecasting errors in the maximum water stage and peak flow.

Select this Article		Runoff Modeling in an Agro‐Forested Watershed Using Remote Sensing and GIS P. K. Gupta, S. Punalekar, S. Panigrahy, A. Sonakia, and J. S. Parihar Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000466 Posted ahead of print 15 June 2011 Full Text: \| Download PDF
	+ -	Show Abstract A hybrid technique was used for the runoff production and its routing in an agro‐forested watershed located within the Kanha National Park in Central India with the use of remote sensing and GIS data. In this technique, modified Soil Conservation Service Curve Number (SCS‐CN) method and a 2D overland flow model were combined. Modified SCS‐CN method estimated daily net rainfall fractions were used as an input to the overland flow model along with other remote sensing derived inputs such as DEM, rainfall, roughness factor etc. for routing of the produced runoff. Model works on cell basis and routs produced runoff from one cell to next following the maximum down slope directions. Flow model uses the diffusive wave approximations of the St. Venant equations for routing surface water. Model was tested by calibrating the Strickler coefficient ‘K’ which is inversely proportional to resistance to flow, and comparing observed and simulated daily change in the water levels for two gauging sites. Calibrated average values of ‘K’ for different sub‐catchments were of 15.7, 21.7, 23.4 and 28.4 for Kurkuti, Sijhora, Between gauging site and Downstream catchments, respectively. Model was tested for some statistical parameters like Nash Sutcliffe coefficient, RMSE, criteria using residuals between observed and simulated data and found to be within the acceptable limits. The results show that hybrid technique works well to extend the application of curve number to address the routing phase of runoff.

Select this Article		Hydrologic Analyses of the 17–18 July 1996 Flood in Chicago and the Role of Urbanization Gabriele Villarini, James A. Smith, Mary Lynn Baeck, Brianne K. Smith, and Paula Sturdevant‐Rees Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000462 Posted ahead of print 14 June 2011 Full Text: \| Download PDF
	+ -	Show Abstract On 17–18 July 1996, two mesoscale convective systems passed through northeastern Illinois causing a record 440‐mm total storm rainfall within a 24‐hr period at Aurora, with values exceeding 200 mm throughout a broad area of the region. The storm caused flooding with a return period larger than 100 years at different USGS regional stream gaging locations. The Davenport WSR‐88D radar coverage allows high quality characterization of the storm at fine spatial and temporal scales. Of particular interest is the inter‐ and intra‐variability in watershed response to the two pulses of intense rainfall. Spatial distribution of rainfall, combined with the degree of urbanization of the individual basins are the dominant factors determining the magnitude of runoff response. These properties are highly dependent on the extent and history of urbanization. Examination of the annual maximum instantaneous peak discharge and the peaks‐over‐threshold time series at three stream gaging stations (Blackberry Creek, Du Page River, and Sawmill Creek) over the past 50 years points to the large impact of urbanization on the flood peak distribution in the greater Chicago metropolitan area.

Select this Article		Simulating Groundwater Inflow in the Underground Tunnel with a Coupled Fracture‐Matrix Model Yong Huang, Zhongbo Yu, and Zhifang Zhou Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000455 Posted ahead of print 10 June 2011 Full Text: \| Download PDF
	+ -	Show Abstract Groundwater inflow during tunnel excavation is one of common problems in practice. How to accurately predict it during the construction is still a challenging problem for tunnel designers. A numerical method, based on the coupled model involved in artery fractures described by discrete fractured network model and ramification fractures and rock matrix described by equivalent continuum medium model, is developed to calculate the groundwater inflow of underground tunnel. The model is calibrated with the observed groundwater levels in the study domain. The results in the model calibration show that calculated and measured groundwater inflows agree well. Sensitivity analysis indicates that groundwater inflow increases with the increase of precipitation rate, hydraulic conductivity of rock matrix and fracture aperture. But the effect of fracture aperture on groundwater inflow is predominated owing to the occurring of many artery fractures around the tunnel, which leads to much groundwater flowing to the tunnel through these fractures.

Select this Article		Curve Number Determination Methods and Uncertainty in Hydrologic Soil Groups from Semi‐Arid Watershed Data Dave Stewart, A. M. ASCE, Evan Canfield, Ph.D., P.E., M. ASCE, and Richard Hawkins, Ph.D., P.E., Life Member, ASCE Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000452 Posted ahead of print 10 June 2011 Full Text: \| Download PDF
	+ -	Show Abstract Four Curve Number (CN) determination methods are evaluated from 16 watersheds in the southwestern U.S. with a total of 1284 events that satisfied a rainfall and runoff criteria. The evaluation found that the use of ordered pairs versus natural pairs of rainfall and runoff data has a larger effect on the CN while the difference in the use of a partial duration series versus an annual series was not significant. The NRCS method of selecting the median CN from the natural pairs of a flood‐peak annual series was found to produce significantly higher CNs than the use of a stable CN value approached with increasing rainfall (CN_∞). The best‐available USDA soil series data were obtained for 20 Arizona watersheds (including the above 16) and 10 groups of New Mexico natural runoff plots. The Hydrologic Soil Groups (HSG) were determined from either direct USDA assignment, or textural properties. These were compared to the HSGs required by the CNs found from above and the cover condition. This study showed a standard error of about 1 HSG, resulting in an error in CN of about 7 units when using the best available data. Compared to the USDA Handbook table values, the CNs found from rainfall and runoff data were higher for 21 of the 30 semi‐arid watersheds.

Select this Article		Curve Numbers for Nine Mountainous Eastern U.S. Watersheds: Seasonal Variation and Forest Cutting Negussie H. Tedela, Steven C. McCutcheon, P.E., M. ASCE, John L. Campbell, Wayne T. Swank, Mary Beth Adams, and Todd C. Rasmussen Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000437 Posted ahead of print 30 May 2011 Full Text: \| Download PDF
	+ -	Show Abstract Many engineers and hydrologists use the curve number method to estimate runoff from ungaged watersheds; however, the method does not explicitly account for the influence of season or forest cutting on runoff. This study of observed rainfall and runoff for small forested watersheds at four sites that span the Appalachian Mountains of the eastern U.S. showed that curve numbers calibrated for the growing season tended to be smaller than for the dormant season. Forest cutting tended to increase curve numbers. However, the increase in water yield following cutting on these Eastern U.S. watersheds only lasted 1 year to 11 years, thereby limiting the precision of the curve numbers estimated for these brief hydrologic effect periods. This study highlights the need to account for seasonality and tree cutting when estimating runoff from some forested watersheds.

Select this Article		The Effect of a Gravel‐Sand Mulch on Soil Water and Temperature in the Semiarid Loess Region of Northwest China Haishen Lü, Zhongbo Yu, Robert Horton, Yonghua Zhu, Jianyun Zhang, Yangwen Jia, and Chuanguo Yang Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000449 Posted ahead of print 28 May 2011 Full Text: \| Download PDF
	+ -	Show Abstract In the semiarid loess region of northwest China, the use of gravel and sand as surface mulching material has been an indigenous farming technique for crop production for over 300 years. A field and modeling study was carried out to quantify the effect of a gravel‐sand mulch on soil water and soil temperature in the semi‐arid loess region of northwest China. The field experiment (April 4, 2001–July 12, 2001) consisted of two treatments, no surface mulching as a control and gravel‐sand surface mulching. HYDRUS‐1D was the numerical model used in the study. The results showed that compared to the non‐mulched condition, the gravel‐sand mulched field had a more favorable soil water and temperature environment for plant growth. In the initial stage of watermelon growth, there was larger soil water storage (3.8 vs 1.9 cm) and soil temperature (10.8 vs 6.2 °C) in the 0–20 cm soil layer with the gravel‐sand mulch. The mulch provided very beneficial water and temperature conditions for the germination of watermelon. The gravel‐sand mulch improved soil water conditions, because it was effective in reducing evaporation and enhancing transpiration. The gravel‐sand mulch also improved infiltration of rainwater. For the 0–20 cm soil layers the average temperature in the gravel‐sand mulch field was 1.0–5.3 °C larger than that in the no‐mulch field. In the 20–40 cm soil layer, the average temperature in the gravel‐sand mulch was 0.3–3.7 °C larger than that in the no‐mulch field. In the early stages of plant growth, plant roots mainly centralized in the 0–40 cm soil layer, and the temperatures under the mulch were conducive to plant growth and development. The field results and the model results consistently showed the value of a gravel‐sand mulch to provide warm, moist conditions for watermelon production in the semiarid loess region of northwest China.

Select this Article		Effects of Vegetation Cover on Hydrological Processes in a Large Region: The Huaihe River Basin, China Chuanguo Yang, Zhongbo Yu, P.E., Zhenchun Hao, Zhaohui Lin, and Huimin Wang Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000440 Posted ahead of print 23 May 2011 Full Text: \| Download PDF
	+ -	Show Abstract Vegetation plays an important role in water and energy cycles on land surface. Nevertheless, vegetation physical effects are not explicitly considered in many hydrologic modelling works. In this study, a coupled land surface — hydrologic model was used to investigate the vegetation effects on hydrologic processes from the year 1980 to 1987 in the Huaihe River Basin, China. Vegetation covers of the basin were assessed by the International Satellite Land Surface Climatology Project (ISLSCP) Initiative II historic and potential land cover dataset. Farmland was declared as the dominant vegetation type of the basin in 1970 by the historic land cover scenario; while potential vegetation cover is mixed forest. Firstly, the coupled model was calibrated by observed streamflow at Bengbu station. Correlation coefficient and Nash‐Sutcliffe coefficient of efficiency of multi‐annually daily series were 0.987 and 0.968, respectively, which indicates a good capability of the coupled model system. And then, typical hydrologic physical processes, including evapotranspiration (ET), soil moisture, surface runoff, and groundwater etc, were simulated and analyzed for the two vegetation scenarios with same meteorological data, initial conditions and model parameters. Results indicate that mixed forest has larger ET than farmland for most rainfall events, and higher soil moisture exists in top layer for mixed forest while lower soil moisture in deep layers due to more transpiration. Surface runoff with mixed forest decreases significantly compared to the simulated values with farmland; and groundwater also reduces because of less drainage and more transpiration with mixed forest. Accordingly streamflow at Bengbu station decreases by about 11% with the potential mixed forest. This study indicates that forestation has an effective influence of reducing peaks of floods.

Select this Article		Runoff Curve Numbers for Ten, Small Forested Watersheds in the Mountains of the Eastern U.S. Negussie H. Tedela, Steven C. McCutcheon, P.E., M. ASCE, Todd C. Rasmussen, Richard H. Hawkins, P.E., M. ASCE, Wayne T. Swank, John L. Campbell, Mary Beth Adams, C. Rhett Jackson, and Ernest W. Tollner, P.E. Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000436 Posted ahead of print 21 May 2011 Full Text: \| Download PDF
	+ -	Show Abstract Engineers and hydrologists use the curve number method to estimate runoff from rainfall for different land use and soil conditions; however, large uncertainties occur for estimates from forested watersheds. This investigation evaluates the accuracy and consistency of the method using rainfall‐runoff series from ten small, forested‐mountainous watersheds in the eastern U.S., eight annual maximum series from New Hampshire, West Virginia, and North Carolina, and two partial duration series from Georgia. These series are the basis to compare tabulated curve numbers with values estimated using five methods. For nine of ten watersheds, tabulated curve numbers do not accurately estimate runoff. One source of the large uncertainty is a consistent decrease in runoff with increasing rainfall when deriving a constant curve number for a watershed. A calibrated constant curve number is suitable for only two of ten watersheds; the others require a variable watershed curve number associated with different magnitude rainfalls or probabilities of occurrence. Paired watersheds provide consistent curve numbers, indicating that regional values for forested‐mountainous watersheds (locally calibrated and adjusted for storm frequency) may be feasible.

Select this Article		An Improved SCS‐CN‐Inspired Model P. Suresh Babu and S. K. Mishra Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000435 Posted ahead of print 21 May 2011 Full Text: \| Download PDF
	+ -	Show Abstract The present study enhances the Soil Conservation Service‐Curve Number (SCS‐CN) predictions by improving the model structure considering the following issues of concern: implementation of antecedent moisture condition procedure, fixation of initial abstraction ratio (λ) at 0.2, usage of the potential maximum retention parameter, and incorporation of storm intensity or duration in runoff estimation. A five‐parameter M3 model is proposed with storm duration and a new parameter, S_abs (potential maximum retention) to overcome most of the above limitations prevailing in the SCS‐CN model. For simplicity and practical applications obviating storm duration data, a four‐parameter M4 model is also proposed. The performance of the suggested and the available models has been evaluated on the data of 82 small watersheds of the United States of America. As demonstrated, M3 model performs the best whereas the conventional SCS‐CN model the poorest among all the models studied.

Select this Article		Fundamental Observation to Clarify the Mechanism of Urban Heat Environment and the Heavy Rainfall in Urban Areas Takuma Kato, Masato Okabe, and Tadashi Yamada Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000192 Posted ahead of print 6 May 2011 Full Text: \| Download PDF
	+ -	Show Abstract The growing need for knowledge about the dynamic behavior of sudden localized heavy rains, however, it is very difficult to observe and predict the behavior of such extreme events. We have been researching to find the reason of the growth and development of locally heavy rains to improve the weather forecast accuracy. This paper covers the following results of researches: Monitoring, experimentation and numerical simulation, this paper presents: an analysis of guerilla rainfalls cases observed with X‐band Doppler radar.

Select this Article		Evaluation of Runoff Responses to Land Use/Cover Changes in the Upper Huaihe River Basin, China Simin Qu, Weimin Bao, Peng Shi, Zhongbo Yu, Peng Li, Bo Zhang, and Peng Jiang Journal of Hydrologic Engineering doi:http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000397 Posted ahead of print 12 March 2011 Full Text: \| Download PDF
	+ -	Show Abstract Runoff changes in response to land use/cover changes in the Huaihe River were drastic in the last few decades and are poorly understood as results from those studies are often equivocal. Hitherto, the methodology to quantify the effects of land use/cover changes on the runoff response has been mainly the paired catchment approach which is a black‐box; and usually restricted to small headwater basins where a control can be established. A model‐based change‐detection approach is developed in this study as an alternative to paired catchment methods. This approach is particularly suited to evaluating effects of land use/cover changes on the hydrologic response in large,to mesoscale watersheds where suitable control is not possible. The Xinanjiang model was used to evaluate the newly implemented approach in the Dapoling watershed (with an area of 1640 km²) in the upper Huaihe river basin. Three schemes were used to examine changes in the data series: 1) Calibration for a period before (or after) changes and simulations of runoff that would have been observed without land use/cover changes (reconstruction of runoff series), 2) Comparison of calibrated parameter values for periods before and after the land use/cover change, and 3) Comparison of runoffs simulated with parameter sets calibrated for periods before and after the land‐cover change. The results show that, since 1976, the medium‐ and high‐coverage natural forest area has decreased, and the corresponding runoff has declined by nearly 25% from 1976 to 2005 due to the continuous expansion of tea gardens and human development. Model parameters, for example, the evapotranspiration coefficient KC, varied considerably from 0.64 to 0.94 due to the land use/land cover change within the watershed. This study demonstrates that the modeling approach may be a useful alternative to the paired watershed approach for examining land use‐land cover changes and their impact on the runoff.