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Select this Article		GoRoSo: A Feedforward Control Algorithm for Irrigation Canals Based on Sequential Quadratic Programming Joan Soler, José Rodellar, and Manuel Gómez Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000507 Posted ahead of print 16 May 2012 Full Text: \| Download PDF
	+ -	Show Abstract The feedforward control canal problem is stated as a nonlinear optimization problem with constraints on the gate movements. It is numerically solved with the use of the Sequential Quadratic Problem (SQP) method and the Active Set. The main objective of the resulting GoRoSo algorithm is the scheduling of the gate openings over a programmed operation scenario and their calculation relies on the use of the Saint‐Venant's complete model over a prediction horizon. A numerical and analytical procedure is developed to quantify the influence of any gate movement over the canal flow conditions for a prediction time horizon. All these influences are lumped together in a global matrix, which is referred to as the Hydraulic Influence Matrix. The GoRoSo algorithm is validated by means of a series of test developed by the ASCE Task Committee on Canal Automation Algorithms.

Select this Article		Effect of Stilling Basin Geometry on the Dissipative Process in Presence of Block Ramps Stefano Pagliara and Michele Palermo Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000505 Posted ahead of print 3 May 2012 Full Text: \| Download PDF
	+ -	Show Abstract The dissipative process occurring in the presence of a hydraulic structure is a major topic in river engineering. The energy dissipation has to be correctly evaluated in order to prevent structural stability risks and optimize the hydraulic performance of the structure itself. Moreover, the analysis of the dissipative process cannot be limited only to the dissipation occurring in correspondence with the structure, but it must also take into account the amount of energy dissipated in the stilling basin. The analysis was conducted considering a block ramp, which is a peculiar stream restoration structure. Experiments were performed in clear water conditions for a fixed ramp slope and different stilling basin geometries. The basin geometry was both symmetrically and asymmetrically enlarged and mobile bed conditions were also tested. It was shown that the global energy dissipation increases for enlarged stilling basins. A simple empirical relationship was derived to evaluate energy dissipation, for both prismatic and enlarged configurations. For asymmetrically enlarged configurations, the flow pattern was analyzed and two hydraulic jump typologies (the Repelled Asymmetric and the Repelled Asymmetric Oscillating) were distinguished and classified.

Select this Article		Soil Moisture Status in an Irrigated Pecan Field Yi Liu and Zhuping Sheng, P.E., M. ASCE Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000503 Posted ahead of print 3 May 2012 Full Text: \| Download PDF
	+ -	Show Abstract In this paper, we modified a traditional transpiration formula using a soil‐gas stress response function of the soil water content to appropriately depict the leave water head. This allows us to identify the soil waterlogging (gas deficit) stress status. We then analyzed the status of soil moisture in an irrigated pecan field in El Paso, Texas using a drainage equation and a modified transpiration formula. In the formula, four soil moisture statuses are identified: waterlogging stress (gas deficit), favorable water uptake, tolerable moisture deficit, and intolerable moisture deficit. Among these, the water uptake favorable status and the tolerable moisture deficit status are the two favorable statuses for healthy pecan growth and good production. Waterlogging (gas deficit) status and intolerable moisture deficit status are detrimental for pecan growth. The results also show that soil moisture status is significantly different during the four growing stages of irrigated pecan: budbreak, early shooting‐leafing, primary shooting‐leafing‐blooming, and fruiting. The results provide guidelines for precision irrigation for achieving water conservation as well as better production of pecans and other similar crops.

Select this Article		Forecasting Spatially Distributed Cotton Evapotranspiration by Assimilating Remotely Sensed and Ground‐Based Observations A. N. French, D. J. Hunsaker, and T. R. Clarke Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000501 Posted ahead of print 2 May 2012 Full Text: \| Download PDF
	+ -	Show Abstract Estimation of spatially distributed evapotranspiration (ET) with remote sensing could be especially valuable for developing water management tools in arid lands. For decision support over irrigated crops, these spatial ET estimates also depend upon good spatial resolution (<30 m) at timely intervals, which for practical operations means no less frequent than approximately five days. For a variety of reasons, current remote sensing platforms usually cannot meet these needs. Commonly overpass frequencies are no better than 16 days, and sometimes are much worse considering cloudy skies. One way to reduce this problem is to develop an ET estimation approach that utilizes both remotely sensed data and ground‐based observations. By combining episodic spatially distributed data with temporally continuous point observations, it could be feasible to provide continuous ET estimates that are better than can be achieved with either technique alone. Using data from a remote sensing irrigation scheduling experiment over cotton, conducted in 2003 at Maricopa, Arizona, an ET modeling approach was developed that used airborne images of vegetation indices (NDVI) and land surface temperatures (LST) along with ground‐based thermal infrared radiometry and meteorology. Fractional vegetative cover were forecast from NDVI at daily time steps using a linear Kalman filter consisting of prior data, cumulative heat units, and spatially oriented Beta distribution functions. LST were forecast hourly using a diurnal temperature model and a linear cover/LST estimator. ET accuracies derived from using these data as inputs to a surface energy balance model showed good agreement with independent ET estimates determined from 5‐day soil depletion observations. Increased ET due to increased crop water use and to irrigation applications were reflected in model outputs, and sometimes agreement was within 10% of independently observed soil moisture depletion data sets. These results indicated that combining remote sensing and ground‐based data sets could be a feasible way to estimate ET at field‐scales at daily time steps.

Select this Article		Performance of Rain Delay Features on a Signal‐Based Evapotranspiration Irrigation Controller D. C. Rutland and M. D. Dukes Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000499 Posted ahead of print 3 May 2012 Full Text: \| Download PDF
	+ -	Show Abstract Evapotranspiration‐based irrigation controllers, also known as weather‐based irrigation controllers, are a new water saving technology that use evapotranspiration (ET) estimates to schedule irrigation. Many ET controllers have the ability to incorporate rainfall events into irrigation scheduling using onsite sensors attached to the controller or weather updates via weather monitoring services. The Toro Intelli‐sense controller can use an onsite rain sensor (rain switch) that immediately interrupts irrigation or a weather service that causes the controller to enter a “rain pause” mode to incorporate rainfall into irrigation scheduling. Four treatments were created using the combination of rain delay features: TN ‐ no rain delay features; TRP — rain pause; TRS — rain switch; TRP‐RS — both rain delay features. A fixed time irrigation schedule with a rain switch and a fixed time irrigation schedule without a rain switch were created for comparison: T — timer with a rain switch; TWORS — timer without a rain switch. During relatively dry periods (72% below historical seasonal rainfall) neither rain pause nor the rain switch resulted in irrigation reduction. However, during periods of rainfall (84% of historical rainy days) both features resulted in significant irrigation savings. The combination of rain switch and rain pause reduced irrigation 41% compared to the use of no rain features, while the rain pause feature alone saved 25%. Due to the variability of rainfall in humid climates it is recommended that both a rain switch and the rain pause feature be used to delay irrigation on the Toro Intelli‐sense controller.

Select this Article		Head‐Discharge Equation for Sharp‐Crested Weir with Piecewise‐Linear Sides Ali R. Vatankhah Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000497 Posted ahead of print 28 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract This research presents a new weir section with n‐segment linear sides and a horizontal bottom. For large n, the section sides of the weir become smooth curves. However piecewise‐linear sides provide a weir shape simple enough for ease of construction. General head‐discharge equations are analytically derived for the flow discharge. The proposed weir with n‐segment linear sides can be applied in optimization procedure to produce a wide range of head‐discharge behavior. An elegant optimization model, that implements the general equations, is presented and applied in the design of the linear and quadratic weirs. This simple model is solved using the Solver toolbox of Microsoft Excel. The versatility of the proposed weir is demonstrated by optimizing the weir parameters, in order to obtain the maximum ranges of measurement under linear and quadratic characteristics. These weirs have least relative error due to their linear and quadratic head‐discharge relationships, and are very useful as a flow recorder in irrigation canals. Optimum design parameters for these weirs are presented in a simple dimensionless form suitable for water structure designers to adjust the weir dimensions to suit the field conditions. Application of the proposed weir section is not limited to these two weirs and proposed section can also be used to design other specific weirs.

Select this Article		Sprinkler Head Geometrical Parameters Effect on Hydraulic Performance of Fluidic Sprinkler Xingye Zhu, Shouqi Yuan, and Junping Liu Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000495 Posted ahead of print 28 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract A new prototype of fluidic sprinkler is proposed in this paper. To determine the discharge coefficient (A), pattern radius (B), sprinkler rotation speed (C), droplet diameter distribution (D) and the radial application pattern (E), several sprinkler heads were specially fabricated to carry out the experiments. After systematic experiments were conducted with the 10PXH fluidic sprinkler, the results showed that the inner contraction angle influenced A, B, C and E. The geometrical parameters of offset length and working area length influenced E. The operating pressure influenced B, C, D and E. The reductions in the radius exactly corresponded to the reduction of the discharge coefficient. As the inner contraction angle increased from 10° to 70°, the pattern radius at 250 kPa decreased from 10.7 m to 8.4 m and the discharge coefficient decreased from 0.9 to 0.67. The time per rotation and the droplet diameter distribution was analyzed, respectively. The radial application pattern at 250 kPa for all nozzles was established. For the square configurations, the smaller the lateral spacing was, the higher the uniformity was.

Select this Article		Evaluation and Regional Calibration of Solar Radiation Prediction Models in Southern Spain Javier Estévez, Francisco L. M. Padilla, and Pedro Gavilán Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000493 Posted ahead of print 25 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Solar radiation (R_s) is a very important variable in agricultural meteorology, but it is measured at a very limited number of weather stations. Also, low quality R_s data are frequent due to sensor failure or no‐calibration. R_s can be predicted from other meteorological measurements (e.g. air temperature), but the accuracy of these methods needs to be tested. In this work, the mechanistic model of Hargreaves‐Samani, three modified versions of this model, a modified Bristow‐Campbell equation and the Mahmood‐Hubbard model were evaluated at fifty six sites in the Andalusian region, southern Spain. All these methods use the daily temperature range of the air (ΔT=T_max⁻ T_min) to estimate R_s. The estimated values of R_s were compared to measurements of R_s to check their suitability. The accuracy of the methods was affected mainly by the magnitude of ΔT, with larger ΔT resulting in a greater accuracy. Finally, the parameter of the Hargreaves‐Samani equation (K_r) was adjusted to regional conditions using ΔT, improving the estimations of incoming solar radiation for a wide of ΔT range.

Select this Article		Using DRAINMOD‐Geostatistical Technology to Predict Nitrate Leaching: A Case Study of Mashtul Pilot Area, Egypt Alaa El‐Sadek, Gehan Sallam, and Mohamed Embaby Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000491 Posted ahead of print 25 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract In Egypt, the Government has initiated large scale projects to reuse drainage water to face the great challenges due to its limited water resources. Taking into consideration the environmental aspects of drainage water reuse, diffuse pollution of water resources from agricultural sources (fertilizers) is a major environmental issue. High percentage of the applied fertilizers is lost due to poor management, which leads to nutrients leaching through different crop rotations. Therefore, there is a need for an integrated precise tool to predict the nitrate leaching to adopt management policies for water quality problems and establish the limits for sustainable drainage water reuse. In order to quantify and analyze the subsurface nitrate leaching, a combination modelling of the system was made in DRAINMOD‐N software.. The study was applied to the Mashtul Pilot Area, Egypt as a case study. Furthermore, the model calculates the future nitrate leaching in the year 2020 for the area. The modeling system combination was applied to the study site to model the nitrate leaching predictions after ten years. The system combination consists of DRAINMOD‐N and Geostatistical Analyst. The study reveals that the modeling system performs well and is reliable and accurate for predicting nitrate leaching. Therefore, this system can help in developing guidelines for drainage design and water management to control the nitrate pollution. The system can potentially be used by policymakers in long‐term strategic management of large scale irrigation development projects.

Select this Article		Machine Learning Approaches for Error Correction of Hydraulic Simulation Models for Canal Flow Schemes Alfonso F. Torres‐Rua, Andres M. Ticlavilca, Wynn R. Walker, and Mac McKee Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000489 Posted ahead of print 25 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Modernization of today's irrigation systems pursues to improve system efficiency and management effectiveness at every component of the system e.g. reservoirs, canals and gates using automation technologies, along with hydraulic simulation models. The resulting canal flow control from the combination of automation and simulation models has proven to be an excellent irrigation water management instrument around the world. Nevertheless, the harsh environment of irrigation systems can induce uncertainties or errors in the components of the canal flow control that can worsen in time misleading or confusing both human and computer controllers. These errors can be attributed to parameter, measurement, and conceptual sources with the complicatedness of locating their individual origin. In this paper a framework is presented to minimize the collective or aggregate error within an irrigation canal flow control scheme that uses a learning machine algorithm (Multilayer Perceptron and Relevance Vector Machine) imbedded into a hydraulic simulation model fed by canal automation system. This framework is evaluated using actual data from an irrigation conveyance canal located at the Lower Sevier River Basin in Utah. The results obtained proved the adequacy of the proposed framework to minimize the aggregate error that affect the simulation results of the automation system (up to 91% in bias, 83% maximum absolute error) over the original values in the verification period. The temporal correlation of the aggregate error was also significantly reduced, thus resulting in reduced local biases and structures in the model prediction error.

Select this Article		Expanding‐Disk Rain Sensor Dry‐Out and Potential Irrigation Savings Leah Meeks, Michael D. Dukes, P.E., Kati White Migliaccio, P.E., and Bernard Cardenas‐Lailhacar Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000487 Posted ahead of print 18 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Rain sensors are devices that connect to automatic irrigation systems to interrupt scheduled irrigation events as a result of rainfall. The objectives of this study were to evaluate the dry‐out time of expanding‐disk rain sensors and determine potential irrigation savings under several virtual irrigation schedules. Five rain sensor model/rainfall set point combinations were evaluated at a research site in north central Florida. The five configurations that were compared were Mini‐Clik® rain sensors with set points of 3, 6, and 13 mm (3MC, 6MC, and 13MC), the Wireless Rain‐Clik (WL) rain sensor, and Toro rain sensor at 6 mm setting (6T). The evaluation period ranged from 1,150 days to 1,182 days across the various devices. For each configuration, data for each time a rain sensor switched between allow to interrupt irrigation modes was collected and compared to how long each stayed in interrupt mode and how much irrigation water a rain sensor could save. Changing the dry‐out vents from fully open to fully closed increased the dry‐out time 14% (3 hours) but had no influence on irrigation savings. The hygroscopic disks significantly dry out 2 or 3 hours after decreasing relative humidity and increasing temperature and solar radiation. Frequent irrigations such as 3 d/wk or higher schedules had more potential savings than less frequent schedules. Savings for the WL, 3MC, 6MC, 13MC, 6T treatments were 9%, 11%, 5%, 8%, and 5%, respectively, compared to a schedule without a rain sensor. Lower set points trended toward higher percent irrigation reduction. Six irrigation schedules were included in the analysis with irrigation depth following University of Florida Institute of Agricultural and Food Sciences net irrigation requirement recommendations: 1, 2, 3, and 7 d/wk with changing irrigation depth based on recommendations, homeowner (HO, 2 d/wk irrigation year round at annual peak ET), and without rain sensor (WORS, 2 d/wk). Comparing schedules to WORS, the average percent water savings for 1 d/wk, 2 d/wk, 3 d/wk, 7 d/wk, and HO was 6%, 8%, 10%, 28, and ‐28%, respectively.

Select this Article		Ultrasonic Flow Measurement for Pipe Installations with Non‐Ideal Conditions Devin M. Stoker, Steven L. Barfuss, and Michael C. Johnson Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000486 Posted ahead of print 13 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract In the arid west, water is among the most valuable of resources. Typically, in order to successfully and accurately measure a flow rate using most types of flow meters, it is recommended that a straight section of pipe be installed immediately upstream from the flow meter to avoid distorted flow patterns and extreme turbulence at the metering location. In many field piping situations, however, such flow conditions are impossible to achieve. The portable ultrasonic flow meter (USFM) is a commonly used flow meter for field flow measurements in closed conduits, which emits two ultrasonic signals across the cross‐section of the pipe. One signal travels with the direction of the flow and the other travels against the flow. The difference in signal travel time is then used along with the known geometry of the pipe to calculate the average flow velocity of the fluid. The performance of an USFM in non‐ideal piping scenarios was studied using laboratory experiments and numerical Computational Fluid Dynamics (CFD) models. A transit‐time USFM was used downstream of a single 12‐inch long‐radius elbow and the error in flow measurement resulting from the flow disturbance was measured. Physical model tests were performed at four locations downstream of the elbow, at three orientations on the circumference of the pipe, and for three flow rates with Reynolds numbers ranging from 250,000 to 750,000. Numerical models were also utilized and the resulting velocity profiles were used to integrate the velocity of the flow across the ultrasonic signal path. The velocity profiles were compared to similar profiles for fully developed flow to determine the error in flow measurement. The USFM measurement errors downstream of the elbow were always negative, and were found to be as great as ‐16%. A correction curve was applied to the results, which provided a method to correct the ultrasonic flow measurement. By applying the correction equation to the USFM measurements downstream of the elbow, the measurement error was reduced by nearly 90%. CFD appears to be a viable tool for making appropriate corrections to ultrasonic flow measurements in pipes with upstream flow disturbances.

Select this Article		Estimating Water Requirements of an Irrigated Mediterranean Vineyard Using a Satellite‐Based Approach S. Consoli and S. Barbagallo Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000484 Posted ahead of print 27 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Quantification of evapotranspiration (ET) is a key factor to design management strategies for improving water use efficiency of irrigated viticulture. In the study, an integrated approach of crop coefficients derived from satellite‐based NDVI, and a daily soil water balance approach was proposed to accurately estimate evapotranspiration fluxes (ET) and crop coefficient values of grapevine plants. The modelled values of K_c and ET were compared with field estimates of crop ET using an energy‐balance Surface Renewal flux tower and adjusted for calibration using the eddy covariance method. The correlation of the measured and modelled K_c exhibits a linear tendency with high coefficient of determination. The study of the soil water balance suggests the importance of soil water storage in grapes. Results of the study validate the use of remote sensing as a tool for accurate estimation of evapotranspiration rates of irrigated grapevine stands.

Select this Article		A New Solution Method for Water Surface Profile along a Side Weir in a Circular Channel Ali R. Vatankhah Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000483 Posted ahead of print 24 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Side weirs are essentially installed along the sides of the open channels. Computation of water surface depth over the side weirs is essential to determine the discharge of the side weir. Analytical solutions for water surface profile along a rectangular side weir are available only for triangular, rectangular and trapezoidal main channels on the basis of a constant specific energy. A circular channel possesses an important application in sewer systems. This research presents an elegant semi‐analytical solution for establishing the water surface profile along a rectangular side weir located in a circular channel which involves the use of incomplete elliptic integrals. The solution is a useful computational tool for evaluation and design of rectangular side weirs in open circular channels.

Select this Article		GIS‐Based Decision Support System for Improved Operations and Efficiency Conservation in Large‐Scale Irrigation Systems Enrique Triana, M. ASCE and John W. Labadie, M. ASCE Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000481 Posted ahead of print 22 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract The long‐term sustainability of irrigated agriculture is contingent on application of cost‐effective water conservation measures and improved management in the face of intense competition for limited freshwater resources from municipal, industrial, and environmental/ecological interests. A GIS‐based decision support system (GeoDSS) is presented for maximizing water savings from efficiency improvements and conservation measures through integrated management of large‐scale irrigation systems. The GeoDSS incorporates the GeoMODSIM network flow optimization model as implemented within ArcGIS™ Desktop (ESRI, Inc.), and is applied to the large‐scale, complex Imperial Irrigation District (IID) water delivery system in California USA in support of the IID/San Diego County Water Authority Water Transfer Agreement. IID GeoDSS automatically constructs a GeoMODSIM flow network within an ESRI geodatabase comprised of feature classes for IID canals, drains, reservoirs, farm gates, interceptors, and pumpback locations. Following calibration of the baseline network, GeoMODSIM simulations predict substantial water savings from mixtures of strategies of varying cost for improved water management, increased delivery system efficiency and on‐farm water conservation, and without the need for fallowing or retirement of IID irrigated lands.

Select this Article		A “Case Study” for the Estimation of Daily Solar Radiation from Measured Air Temperature Extremes in the Mid‐Mediterranean Area G. Grillone, C. Agnese, and F. D'Asaro Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000480 Posted ahead of print 22 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Daily solar radiation R_s at ground level is a necessary input variable required for the evaluation of evapotranspiration and crop growth, development and yield simulation models. Nevertheless, it is measured in a few weather stations and at many locations it is not observed; besides, available R_s temporal series are generally no longer than a few years. A valid surrogate of R_s measurement is the diurnal air temperature range (ΔT); indeed, ΔT is inversely proportional to the cloudiness and therefore could be a good indicator of atmospheric transmittance. As opposed to R_s, daily maximum and minimum air temperatures are measured at many locations and their observations in developed countries began since the 19^th century. For this reason, several models, which permit R_s indirect evaluation from air temperature data, have been suggested in the literature. The most famous models are the simple Hargreaves‐Samani (HS) formula (1982), many times re‐calibrated by the authors (Hargreaves 1994; Samani 2000), and the Bristow‐Campbell model (1984), recently improved by Donatelli and Campbell (1998) and Donatelli and Bellocchi (2001). In this paper, the suitability of each proposed model is tested by comparing R_s real data, recorded in 33 Sicilian agro‐meteorological stations in the period 2003–2008, typically representing the Mid‐Mediterranean area, with R_s estimates obtained by the models from ΔT data. In addition, a regional relationship is obtained for the scale coefficient K(T) of the Hargreaves‐Samani formula: the relationship found improves R_s data prediction with respect to the original HS formulation.

Select this Article		Quadrangle Downscaling of Global Climate Models and Application to Riyadh Zekâi Şen, A. Al Alsheikh, A.S., A. M. Alamoud, A. A. Al‐Hamid, A. S. El‐Sebaay, and A. W. Abu‐Risheh Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000478 Posted ahead of print 16 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Climate change impact reports by Intergovernmental Panel on Climate Change (IPCC) are well established throughout the world. By now many local, regional and central authorities are aware of these impacts and they try to take necessary precautions according to their environmental circumstances. Preliminary decisions cannot be taken unless there is a model for future climate change impacts especially for rainfall occurrence, amount and frequency estimations. The main purpose is to combine the General Circulation (Climate) Model (GCM) outputs with the local meteorology station records by a suitable downscaling procedure. In this paper, a statistical quadrangle downscaling model (QDM) is developed for rainfall estimations up to 2100. This model helps to downscale the nearby four scenario rainfall amounts at GCM grids to desired point. Two main steps in the model structural are the use of regional dependence function (RDF) for transferring the GCM output data from four nearest grid points to the location. The second step is to adjust the downscaled scenario monthly rainfalls with the local rainfall records. The GCM monthly rainfall outputs are downloaded from the National Center for Atmospheric Research (NCAR) with special report emission scenario A2. The application of the methodology is presented for Riyadh City, Kingdom of Saudi Arabia (KSA). The RDF is obtained from the most reliable meteorology records at 27 locations that are irregularly scattered all over the country. The RDF and then it is used for scenario data transfer from the regular grid points. The adjustment is based on the average statistical properties of concurrent monthly rainfall amounts between 1985 and 1996. The trend component in the GCM remains intact. It has been observed that there is a major increasing trend in the monthly rainfalls after 2050. In the meantime each decade starting from 2011 gives estimates that indicates steadily rainfall increases up to 2050. The QDM indicates 40% increase in the annual total rainfall amounts with 15% standard deviation increase.

Select this Article		Standardization of Reference Evapotranspiration Models for a Sub‐Humid Valley Rangeland of Eastern Himalayas Bhabagrahi Sahoo, Imtisenla Walling, Bidyut C. Deka, and Bhagwati P. Bhatt Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000476 Posted ahead of print 7 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract For efficient irrigation water management and hydro‐meteorological studies at both the field and catchment scales, there is a need to evaluate the existing evapotranspiration (ET) estimation methods under varied physiographical and data availability conditions. In this study, using the ASCE‐FAO‐56 Penman‐Monteith model as the benchmark model, a total of 16 various ET estimation methods (viz. FAO‐24 Radiation, Hargreaves Radiation, Hargreaves Temperature, Priestley—Taylor, Jones—Ritchie, Makkink, Turc, Modified Jensen—Haise, Snyder et al. pan, FAO‐24 pan, Cuenca pan, Allen‐Pruitt pan, Snyder pan, Pereira et al. pan, Orang pan, and Raghuwanshi—Wallender pan evaporation) were evaluated using both the continuous daily timeseries and average timeseries weather data of a sub‐humid valley cultivated rangeland of eastern Indian Himalayas. The results revealed that the Priestley—Taylor, Turc, Snyder et al. pan, FAO‐24 pan, Snyder pan, and Pereira et al. pan evaporation models have restricted performances. Consequently, for an improved performance, all these models were standardized using a Genetic Algorithm based linear corrector transformation model. Almost all the models perform reasonably well while using the average daily timeseries data. Further, the trend analysis of reference ET showed that there is an increasing trend during the months of February to July including October, and decreasing trend during August to January except October, with an annual decreasing rate of 0.42 mm/year.

Select this Article		Optimal Allocation of Resources for the Maximization of Net Agricultural Return Ajay Singh Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000474 Posted ahead of print 5 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Good quality soil and water resources are often limited in arid and semi‐arid regions; however, poor quality groundwater can be used conjunctively with good quality canal water to fulfill crop water demand in these areas. In the present study, a linear programming model was developed for the optimal land and water resources allocation in order to maximize net annual returns from a command area located in Jhajjar district of Haryana, India. The water production functions were developed and incorporated in the model to estimate the crop yield under different qualities of irrigation water. A groundwater balance constraint was imposed on the model, which mitigate the waterlogging problems, while making optimal allocation of land and water resources. The model results show a reduction in rice and mustard areas against an increase in cotton, sugarcane and wheat under optimal conditions. Under the optimal land and water allocation the groundwater use is increased, which in turn mitigated the waterlogging and salinity problems of the command area. The net annual return from the command area has increased by more than 20% under optimal allocations. The sensitivity analysis of the model parameters show that better price of crops is most sensitive parameters followed by the crop area and cost of cultivation. State agencies and farmers involved in the actual agricultural production process are advised to practice conjunctive use of canal water and groundwater to maximize their farm income. This strategy could also mitigate further rise in the watertable in the command area without installing expensive drainage systems, which is also not feasible because the groundwater quality is poor and drainage water may pose a serious disposal problem.

Select this Article		Study on the Accelerated Life Test for Durability of Irrigation Micro‐Sprayer Hua Zhao and Di Xu Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000475 Posted ahead of print 5 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract The test time, the time the failure occurred, and the service life of micro sprayers of accelerated life tests are analyzed and compared with those of normal life tests based on the life distribution and parameters determined by the test date. The feasibility of adopting an accelerated life test to improve the efficiency and durability of micro sprayers is investigated accordingly. The testing time in the normal life test can be shortened by about 50% using the accelerated life test; the relative error in the service life estimation between the two tests is 1%–11%; and the relative error of the average service life estimation is 5% at different confidence levels. The estimation of the service life of a micro sprayer obtained from the accelerated life test can substitute the result of the normal life test for reducing the test time under the condition of the error tolerance of the distribution parameters.

Select this Article		An Appraisal on the Use of Urban Weather Data to Estimate Reference Evapotranspiration for Rural Irrigation Management Yufeng Luo, Yunlu Jiang, Shizhang Peng, Shahbaz Khan, Xueliang Cai, Weiguang Wang, and Xiyun Jiao Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000470 Posted ahead of print 3 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Weather data measured in urban areas are generally more easily available than those in rural areas. If the urban weather data are used to calculate the reference crop evapotranspiration (ET₀) for rural irrigation management or spatial and temporal trend analysis, the results may be biased due to the differences in weather variables. We collected daily data for mean, maximum and minimum temperatures, relative humidity, average wind speed and sunshine duration from two stations: Kaifeng Station in the City of Kaifeng and Huibei Station in the nearby irrigation scheme for 1984–2009. ET₀ for both stations were calculated using the FAO‐56 Penman‐Monteith method and compared. The results indicated that the difference in daily ET₀ was remarkable (with relative error of 52.6%), the difference between monthly average ET₀ increased gradually during the last three decades and the temporal trends in annual average daily ET₀ were opposite. There were significant differences in ET_c (with RE of 31.1%) and irrigation requirements (with RE of 24.3%) between the two stations. Even thhe distance between the two stations is only 20 km, the urban weather cannot be used to estimate ET₀ for rural irrigation management.

Select this Article		A Model for Nonlinear Root Water Uptake Parameter Vijay Shankar, K. S. Hari Prasad, C. S. P. Ojha, M. ASCE, and Rao S. Govindaraju Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000469 Posted ahead of print 3 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract An empirical relationship is developed for the nonlinear root water uptake parameter in the O‐R moisture uptake model from easily measurable plant physiological parameters such as maximum daily transpiration, maximum root depth, and time to attain the maximum transpiration. A non‐dimensional parameter, termed specific transpiration, involving the plant physiological parameters is used in this empirical relationship. Data for determining this relationship are obtained my minimizing the deviations between the field observed moisture depletions of 28 crops reported in literature and the Richards equation‐based numerically simulated soil moisture depletions combined with the moisture uptake model accounting for root water uptake. Apart from a cross‐validation, field experiments on three Indian crops ‐ maize, Indian mustard and wheat are conducted to further validate the proposed empirical relationship. Comparisons of model predictions with field observations of soil moisture profiles and moisture depletions in different layers of the root zone show good agreement during different stages of crop growth. The results highlight the utility of the developed equation for modeling root water uptake over a wide range of crops

Select this Article		Vipmet: A New Real‐Time Data Filtering Based Automatic Agricultural Weather Station J. M. Molina‐Martinez, P. J. Navarro, M. Jimenez, F. Soto, A. Ruiz‐Canales, and D. G. Fernandez‐Pacheco Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000468 Posted ahead of print 3 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Agricultural weather stations are normally utilized to register weather variables (e.g. temperature, relative air humidity, solar radiation and wind speed). These data can be used to estimate daily and hourly reference crop evapotranspiration (ETo), which can provide important information for water resources optimization in irrigation scheduling. However, data captured by actual agricultural weather stations are not filtered, what may lead to a bad estimation of the parameters and consequently to a deficient water management, endangering the horticultural crops. This paper presents a new automatic agricultural weather station that is endowed with a real‐time data filtering process to ensure the validation of the acquired data. In addition, the station can be remotely controlled for automatic data collection and management tasks by means of a 3G mobile router. A comparison between data registered by the station and data supplied by the nearest Murcian Agricultural Information Service (Spain) was carried out for evaluation purposes.

Select this Article		The Effect of the Capillary Fringe on Steady‐State Water Tables in Drained Lands E. G. Youngs Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000467 Posted ahead of print 3 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract When the flow in the capillary fringe above the water table is taken into account in land‐drainage theory, water‐table heights are lower than those predicted when incident rainfall on the surface is assumed to travel vertically through the vadose zone. An analytical solution is given here to the steady‐state drainage problem of the flow of surface‐incident rainfall to cylindrical drain channels for the situation of a completely tension‐saturated soil above the water table. This gives the maximum effect that the unsaturated soil region above the water table can have on the water‐table height for the given drainage system. Calculated results show that the water‐table height above drain level is smaller for deeper drains below the soil surface and for larger drain radii than is the case when the effect of the capillary fringe is ignored. It follows that drainage design based on customary land‐drainage theory ignoring the effect of a capillary fringe, gives an over‐estimate for the drain spacing.

Select this Article		Labyrinth Weirs: Nappe Interference and Local Submergence B. M. Crookston, A. M. ASCE and B. P. Tullis, M. ASCE Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000466 Posted ahead of print 13 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract The interaction of nappes from adjacent weir walls near an upstream apex can cause local submergence, which reduces labyrinth weir discharge efficiency. Local submergence effects can cause the head‐discharge relationships for labyrinth weirs of equivalent length but different cycle number to differ. Empirical labyrinth weir discharge coefficients implicitly account for apex effects and local submergence; however, the uncertainty associated with applying hydraulic design data developed from specific weir geometries to comparable but different labyrinth weir geometries is not well understood. This study investigated the concept of labyrinth weir nappe interference and identified labyrinth weir flow characteristics that decrease discharge efficiency, including local submergence. Parametric methods for quantifying nappe interference region size as a function of weir geometry (e.g., sidewall angle, crest shape) and flow conditions (e.g., headwater, nappe aeration) are presented. A comparison between empirical methods found in the literature for determining the size of the nappe interference region and laboratory‐scale experimental data showed limited correlation. The data presented in this study are recommended as a more accurate alternative to predict the extent of the nappe interference region.

Select this Article		Piano Key Weir: Reservoir vs. Channel Application R. M. Anderson and B. P. Tullis, M. ASCE Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000464 Posted ahead of print 9 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract The piano key or PK weir is a relatively new non‐linear weir geometry that can be used to increase spillway discharge capacity over linear weir geometries, particularly when the weir footprint is restricted (e.g., spillways on the crest of a concrete dam). The majority of the published PK weir research (e.g., head‐discharge curves) has been based on channelized applications (sectional PK weir models in laboratory flumes). The head‐discharge characteristics of crest‐of‐dam PK weir applications are influenced by the approach flow conditions. Using a laboratory‐scale physical model, the hydraulic efficiency of a PK weir design was tested with varying approach flow depths, upstream apron slopes, and abutment details. In general, discharge efficiency increased with increasing approach flow depth, steeper approach aprons, and improved abutment geometries that reduced the effects of flow separation.

Select this Article		Characterization of Pumps for Irrigation in Central California: Potential Energy Savings Luis Pérez Urrestarazu and Charles M. Burt, M. ASCE Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000463 Posted ahead of print 9 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract Many pumps are used for irrigation in Central California but a great number of them are operating inefficiently. In this paper, the information recovered from over 15,000 electric irrigation pump tests in Central California is analyzed. The objectives of this study are to define the common characteristics attributed to pumps with best and worst performance and to identify the possible target groups that might benefit from improvements, obtaining potential energy savings. The results showed that pumps with lower reported Total Dynamic Head (TDH) and flow rate (Q) usually have poorer overall pumping plant efficiency (OPPE) values but high flow rates and input power are typically associated with better OPPE values. According to this analysis, energy savings of more than 100,000 MWh/year could be achieved for well pumps, with a per‐pump average of 50 MWh/year. For non‐well pumps, the total potential savings are 16,500 MWh/year and the average per pump is 34 MWh/year.

Select this Article		Errors in Infiltration Calculations in Volume Balance Models E. Bautista, A. M. ASCE, T. S. Strelkoff, M. ASCE, and A. J. Clemmens, M. ASCE Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000462 Posted ahead of print 9 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract Volume balance models of surface irrigation calculate the infiltrated volume at a given time as a product of the stream length, upstream infiltration, and shape factors. The best known expression of this type was derived by combining the Lewis‐Milne equation with empirical power‐law expressions for infiltration and advance as functions of time. This expression results in systematic errors that are not well understood by users of volume balance methods. This article examines those errors in furrow irrigation by comparison with infiltrated volumes computed with zero‐inertia simulation. The potential for errors is greatest with light soils and where the bottom slope is large enough to produce kinematic flow conditions. An example is presented to show how these errors in a parameter estimation problem based on a volume balance can be corrected iteratively with the help of zero‐inertia simulation.

Select this Article		Improved Surface Volume Estimates for Surface Irrigation Volume Balance Calculations E. Bautista, A. M. ASCE, T. S. Strelkoff, M. ASCE, and A. J. Clemmens, M. ASCE Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000461 Posted ahead of print 9 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract This article reviews procedures for estimating surface storage in surface irrigation volume balance calculations. Those procedures are based on the assumption of a power law relationship for flow depth as a function of distance along the stream. The analysis uses zero‐inertia simulation and a system of dimensionless variables to examine how the depth profile varies as a function of hydraulic conditions when infiltration is given by the empirical Extended Kostiakov equation. Alternatives for approximating the exponent of the depth profile power law (β) are suggested. The magnitude of the resulting errors relative to zero‐inertia model predictions is quantified. Results show that the range of variation for the parameter β increases with field slope, with increasing advance length relative to the maximum advance distance, and when infiltration rates are relatively constant with time during the irrigation event. Estimating β as a function of advance distance is most challenging under these conditions. Potentially large errors in the determination of β do not undermine the proposed procedures when the surface volume represents only a small fraction of the applied volume. Users of volume balance procedures need to be aware of conditions where uncertain surface volume calculations can lead to potentially large volume balance errors and, thus, where results need to be interpreted carefully.

Select this Article		Impacts of Hay Mulch on Soil Properties and Potato Tuber Yield under Irrigation and Non‐Irrigation in New Brunswick, Canada Zisheng Xing, Pat Toner, Lien Chow, Herb W. Rees, Sheng Li, and Fanrui Meng Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000459 Posted ahead of print 9 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract Organic mulching and irrigation have been considered important soil conservation and agricultural practices. However, the effectiveness of these practices on soil properties and potato production in the relatively cool, moist maritime region of Canada has not yet been well studied. In the growing seasons of 2000–2003, a field experiment was conducted at the Potato Research Centre, Agriculture and Agri‐Food Canada, Fredericton, New Brunswick, to assess the benefits of hay mulching on a loamy sand soil under potato production. Treatments consisted of four levels of hay mulching: 0, 2.25, 4.5, and 9.0 Mg ha⁻¹ with four replicates under irrigation or non‐irrigation. Results showed that hay mulching could help to conserve soil moisture in non‐irrigation treatments with an increase of mean soil moisture content by 5.7 to 9.5% under 2.25 to 9.0 Mg ha⁻¹ of hay mulch compared with control. The greatest conservation effect on soil water in our region would be achieved with a mulch rate of 5.6 Mg ha⁻¹. Under irrigation, mulching slightly increased soil temperature. Without irrigation, soil temperature was affected both positively and negatively by mulching, depending on time of day, and amount of mulch applied. During periods of warmer weather, mulching reduced maximum soil temperature during daytime but increased minimum soil temperature during nighttime. While the magnitude of soil temperature change was slight it varied linearly with amount of mulch. During periods of cold weather, mulching generally increased soil temperature. The soil organic carbon content in the year following mulching increased proportionally with the amount of mulch applied in the non‐irrigated treatments. Thus, thicker mulching treatments resulted in a greater increase in soil organic matter accumulation. Irrigation was found to potentially induce organic matter loss for the lower mulching treatment (2.25 Mg ha⁻¹) and control. We did not find any significant impacts of hay mulching on total potato tuber yield under irrigation, but tuber yield under non‐irrigation increased linearly with the amount of mulch applied.

Select this Article		An Optimization Model for BMPs Placement in a Reservoir Watershed Shih‐Kai Ciou, Jan‐Tai Kuo, Pin‐Hui Hsieh, and Gwo‐Hsing Yu Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000458 Posted ahead of print 9 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract The purpose of this study was to develop an optimization model for the optimal placement of structural BMPs (Best Management Practices) at the watershed scale for a reservoir. In this research, three types of structural BMPs were considered, i.e. a wet detention pond, grass swale and infiltration trench. The complete model consists of three interacting sub‐models: a watershed water quality simulation model, Hydrologic Simulation Program‐Fortran (HSPF), a reservoir water quality model (CE‐QUAL‐W2 model) and an optimization model based on GAlib, a well‐developed Genetic Algorithm (GA) software. This research used Feitsui Reservoir and its watershed in northern Taiwan as the area of application. For the optimization model, the objective function was to minimize the total annual cost of BMPs, within the constraints of achieving minimum water quality standards for the concentrations of phosphorus, ammonium, nitrate‐nitrite and total suspended solids in the reservoir. The study first simulated the discharge and pollutant loads for the watershed in 2002–2003 using HSPF. The reservoir model CE‐QUAL‐W2 was then used to simulate variations in pollutant concentrations in the reservoir based on the input discharge and pollutant loads from HSPF. The optimization model was finally used to search for the near optimal selection and placement of BMPs in the watershed. The results obtained from the completed model effectively demonstrate its viability in improving water quality in the reservoir by adopting optimal BMPs placement strategies.

Select this Article		Roughened Channels with Cross Beams Flow Features Rita Fernandes de Carvalho and Manuel Lorena Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000457 Posted ahead of print 6 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract The implementation of roughened channels with cross beams (RCCB) in drainage systems reduces the negative effects of high kinetic energy on flood flows, such as the increased erosion of infrastructures or of the ground. Through an adequate placement of cross sills or beams, the flow produces successive hydraulic jumps (tumbling flow) characterised by excessive air entrainment and turbulence. This paper aims to highlight the importance of using RCCB in drainage systems and to contribute to a better knowledge of flow characteristics in roughened channels with cross beams (RCCB). The performance of RCCB was studied under diverse conditions through the use of a physical model, where several cross beams were installed with different thickness, longitudinal spacing between them and at different heights. Results of free surface profile, pressure head and velocity measurements for different arrangements of slopes, cross‐beam dimensions and spacing were compared with the scarce data available in literature and put together to form equations, which revealed important features of flow estimate. This paper proposes empirical relations to predict flow characteristics in the engineering practice dealing with RCCB design, such as discharge limit, maximum flow, water depth and friction factor. In particular, it shows that energy dissipation in roughened channels with cross beams increases about 30% in relation to channels where cross beams are not used.

Select this Article		Comparison of Multilevel Calibration and Volume Balance Method for Estimating Furrow Infiltration B. Moravejalahkami, B. Mostafazadeh‐Fard, M. Heidarpour, and F. Abbasi Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000456 Posted ahead of print 1 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract Furrow irrigation is one of the oldest methods of irrigation in which the soil surface is used to convey and infiltrate water. The most important problem in the path of improving furrow irrigation performance is the difficulty of estimating the infiltration function. In this study multilevel calibration method and volume balance approach were used for estimating the Kostiakov‐Lewis infiltration equation parameters and roughness coefficient for the constant and cutback inflow hydrograph shapes for furrow irrigation using field data. The multilevel calibration method predicts the total volume of runoff and infiltration with less relative error than the volume balance approach. The results of this study indicated that the simple volume balance approach and the multilevel calibration method predicted infiltration equation parameters and roughness coefficient with nearly the same accuracy but the volume balance approach involved shorter execution times as it required less iteration through the simulation algorithms than the multilevel calibration method.

Select this Article		Hydraulic Performance of Asymmetric Labyrinth Side Weirs Located on a Straight Channel A. Parvaneh, S. M. Borghei, and M. R. Jalili Ghazizadeh Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000455 Posted ahead of print 1 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract This paper details a new design for labyrinth side weirs, which has been tested and analyzed. The proposed geometry for this labyrinth side weir differs from a triangular labyrinth side weir, in that it is asymmetric in plan. The hydraulic behavior of the present labyrinth side weir, with a constant opening length, different weir heights and asymmetric labyrinth side weir included angles has been experimentally investigated in the subcritical situation. Based on the analysis of more than 180 experimental data, an equation for discharge coefficient of the asymmetric triangular labyrinth side weir has been presented. The results show that the discharge coefficient of the asymmetric labyrinth side weir is up to 1.6 and 2.35 times more efficient than a symmetric labyrinth and rectangular side respectively.

Select this Article		A Semi‐Quantitative Analysis of Water Approapriations and Allocations in the Upper Rio Grande Basin, Colorado Ken Mix, Vicente L. Lopes, and Walter Rast Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000436 Posted ahead of print 6 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract A semi‐quantitative analysis was used to assess the impacts of water rights appropriations and allocations in the Upper Rio Grande (URG) Basin, in Colorado, USA. The study also explores the causes and effects of the changes on collateral elements in the URG agriculture system, namely the San Luis Valley (SLV). Population increases, after the acquisition of the territory from 1854 to 1900, were the major cause of increased acquisitions of surface water rights. By 1912 surface waters were nearly 100% appropriated. The population continued to increase until 1930 after which it remained stable. Water users began making large increases in the number of appropriations of groundwater around 1925, with the majority of increases starting around 1935. As a result, moratoriums were placed on well development in the 1970s and 80s. Individual ‘spikes’ in water rights acquisitions of surface and groundwater were associated with periodic droughts and high crop prices. Change point time series analysis identified three major periods of acquisition of waters rights: 1881–1911 for surface water, 1935–1981 for the unconfined aquifer, and 1945–1967 for the confined aquifer. Collateral effects on stream flows and agricultural acreage also were evident. The annual stream outflows from the SLV declined by 400 hm³ after 1924, being attributed to surface water extractions. An additional reduction in outflow of 60 hm³ from 1925 to 1963 was attributed to groundwater extraction. An increase in agricultural acreage by 80,000 ha during the period 1948–1978 fostered increases in groundwater rights acquisition from 1935–1981.

Select this Article		Modified Hargreaves‐Samani Equation for the Assessment of Reference Evapotranspiration in Alpine River Basins Giovanni Ravazzani, Chiara Corbari, Stefano Morella, Paride Gianoli, and Marco Mancini Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000453 Posted ahead of print 20 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Deriving accurate estimates of reference evapotranspiration is required for water resources management, irrigation water requirement computations and successfully hydrological modelling. The Food and Agriculture Organization of the United Nations (FAO) recommended the Penman‐Monteith equation as the standard for estimating reference evapotranspiration. Alternative method for application at sites where only air temperature measurements are available is the Hargreaves‐Samani equation. The main objective of this study is to investigate the possibility for application of Hargreaves‐Samani equation in Alpine area for computing daily reference evapotranspiration. An evaluation of the Hargreaves‐Samani equation and its modifications proposed in literature is made by comparing daily estimates with Penman‐Monteith results at 51 meteorological stations in the upper Po river basin (Italy) and the Rhone river basin (Switzerland). Significant error was encountered in all methods based on Hargreaves‐Samani equation. A relationship for adjusting Hargreaves‐Samani coefficient based on local elevation is proposed, calibrated and validated. The resulting modified Hargreaves‐Samani equation showed a significant reduction of error for estimating daily reference evapotranspiration. The proposed equation is not intended for replacement of Penman‐Monteith method but to be used for application in Alpine river when only air temperature data are available.

Select this Article		Rasgeminec Model for Sectoring Optimization in Pressurized Irrigation Networks Using Simulated Annealing Approach Alberto García Prats, Santiago Guillem Picó, Fernando Martínez Alzamora, Miguel Ángel, and Jiménez Bello Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000452 Posted ahead of print 19 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract A pressurized irrigation network may operate in two ways, namely: on‐demand and organized under operating sectors. In the first case, the user decides when to irrigate, and the pumping station has to meet the discharge and pressure head requirements of the group of users that is demanding water at any time. In the second case, the operating hydrants at a given moment are previously established, which permits identification of scenarios related to lesser energy consumption. In this work, a new model was developed that identifies such scenarios. The optimization process is carried out by means of Simulated Annealing (SA). The model was applied to an example and the result obtained was compared with the same network operating on demand and sectorized using the criterion of hydrant elevation with respect to the pumping station. The scenario adopted for SA allows for saved 11.8 % and 15.5 % in energy consumption compared to the two other scenarios, and decreased the installed power requirement with 38.3 % and 21.6 % respectively.

Select this Article		Discharge Efficiency of Reservoir‐Application‐Specific Labyrinth Weirs B. M. Crookston and B. P. Tullis, M. ASCE Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000451 Posted ahead of print 19 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Published labyrinth weir designs, which have primarily been developed based on labyrinth weir test data from laboratory flumes, are specific to in‐channel labyrinth weir applications where the approach flow is oriented normal to the weir axis. Consequently, some uncertainty exists regarding the hydraulic performance of labyrinth weir configurations that are specific to reservoir applications (i.e., Projecting, Flush, Rounded Inlet, and Arced labyrinth weirs). The discharge efficiency, as characterized by the weir discharge coefficient, of laboratory‐scale Projecting, Flush, Rounded Inlet, and Arced labyrinth weirs with 12° sidewall angles, were evaluated as a function of H_T/P and compared with in‐channel labyrinth weir discharge efficiencies. The Arced labyrinth weir configuration had a higher discharge efficiency (∼5 − 11% higher) than an In‐Channel labyrinth weir orientation. In general, the Projecting, Flush, and Rounded Inlet orientations were less efficient than the In‐Channel labyrinth weir configuration.

Select this Article		Estimating Daily Surface Soil Moisture Using a Daily Diagnostic Soil Moisture Equation Feifei Pan Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000450 Posted ahead of print 19 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract There is one common problem associated with water balance calculation methods for determining soil moisture for scheduling irrigation, i.e., the errors in the estimated soil moisture are cumulative and a regular recalibration is needed. A simple and robust approach to estimate daily soil moisture using a daily diagnostic soil moisture equation is suggested and studied. The estimated soil moisture is a function of the time‐weighted summation of the ratio of historical precipitation rate to the soil moisture loss coefficient. To capture the seasonal variation of soil moisture loss coefficient, a sinusoidal wave function of the Day of Year (DOY) is used to represent the seasonal variation of the loss coefficient. A three‐year continuous dataset of daily soil moisture and daily precipitation collected at each of four Soil Climate Analysis Network (SCAN) sites, i.e., AR2091 in Arkansas, GA2013 in Georgia, NM2107 in New Mexico, and PR2052 in Puerto Rico, is applied to test the proposed method. The land cover and land use of these four sites are agricultural/crop fields, grasslands, or desert. The root mean square errors of the estimated volumetric soil moisture are less than 5%(V/V) and the correlation coefficients R² are all greater than 0.78. The results indicate that there are three advantages associated with the suggested approach: 1) non‐cumulative errors in the estimated soil moisture, and thus 2) no regular recalibration requirement, and 3) no numerical iteration and initial moisture information needed.

Select this Article		Performance Analysis and Calibration of a New Low‐Cost Capacitance Soil Moisture Sensor George Kargas and Konstantinos X. Soulis Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000449 Posted ahead of print 19 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Several newly developed sensors based on capacitance and frequency techniques have simplified real‐time determination of soil water content (θ). The 10HS sensor (Decagon Devices Inc., Pullman, WA, USA) is one of the most recent developments in capacitance sensors. However, up to now, little is known about the accuracy of this sensor, and the dependency of its measurements on soil type and environmental factors. In this study, the performance of 10HS sensor was investigated through experiments using liquids with known dielectric properties and experiments in a set of porous media exhibiting a wide range of properties. The response of the 10HS sensor in bi‐layered systems was also investigated. The experimental results suggested that there is a distinct instrument sensitivity to soil type, indicating the need for individual soil calibration. A set of specific calibration equations for the various porous materials studied were proposed. It was shown that the 10HS sensor is able to provide reasonably accurate relative permittivity (ϵ_r) measurements, but the manufacturer's ϵ_r calibration equation, to some extent, overestimates ϵ_r in the full range of the measured values in liquids. The sensor to sensor variability was also found to be relatively small. It was shown that the manufacturer's calibration equation for measuring θ “version 1” underestimates θ, while “version 3” overestimates θ, in all porous materials examined. The most accurate results were provided by the proposed soil specific calibration equations obtained using the multi‐point calibration equations. However, the two‐point calibration equations reasonably represent θ in all porous media tested. Underestimation of soil moisture with increasing temperature in coarse porous media and overestimation in fine porous media were observed. The temperature dependence was more important in the fine porous media. The effect of electrical conductivities in sand was also examined and it was found to be negligible. Finally, the sensors' response in bi‐layered systems generally follows the refractive averaging scheme at lower ϵ_r values, and the arithmetic averaging scheme at higher ϵ_r values.

Select this Article		Evaporation Studies of Canopy Covered On‐Farm Reservoir Bharat C. Sahoo, Sudhindra N. Panda, M. ASCE, and Pravin Patil Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000448 Posted ahead of print 17 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract In the present study, fifteen existing evaporation models based on flux gradient, energy balance and mass transfer approaches are used to estimate the rate of evaporation from regular sized open on‐farm reservoir (OFR). Statistical analysis has been carried out for screening of the models. Root mean square errors (RMSE), per cent deviation, coefficients of determination (R²) and scatter plot analysis reveal that three out of fifteen models, namely, Bowen ratio energy budget (BREB), Priestley‐Taylor and deBruin‐Keijman are predicting the evaporation rate from open on‐farm reservoir in proximity with the actual evaporation recorded by class A pan evaporimeter. Further, these selected models are used to predict the evaporation rate from the canopy covered on‐farm reservoir taking into consideration the weather parameters in their micro environment. The depletion of water level in the OFR recorded daily by a graduated staff gauge and the change in water spread area are taken together to compute the actual evaporation rate from the water bodies. As observed, average evaporation rate from the canopy covered OFR was about 1.18 mm less than that of a similar open OFR per day. Reduction in evaporation loss due to canopy cover over the OFR in comparison to an open one to the tune of 35% during winter season (October to February) indicates the efficacy of the biological measure in mitigating the loss of scarce natural resource (rainwater) in rainfed areas.

Select this Article		Design and Validation of a Test Rig to Simulate High Rainfall Events for Infiltration Studies of Permeable Pavement Systems Ernest O. Nnadi, Ph.D., Alan P. Newman, MSc. LLM, Les Duckers, Ph.D., Stephen J. Coupe, Ph.D., and Susanne Charlesworth, Ph.D. Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000446 Posted ahead of print 4 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract This paper reports the design and validation of a relatively cost‐effective test rig to simulate high rainfall events which offers a great opportunity for conducting studies (e.g high infiltration studies) that requires high intensity of rainfall on pervious pavements and other permeable systems. The calibration of the test rig which produced over 600mm/hr rainfall intensity was successful. A simple method of using digital photography to capture raindrops and determine raindrop diameter was developed and used successfully to determine the drop size of simulated rainfall by the test rig. Results obtained by this method indicated that the raindrop diameter varied from 0.69 – 8.97mm and consistent with the high rainfall intensity generated by test rig. Categorization of rain drop size according to Wilson Bentley's Classification showed 1.84%, 6.42%, 33.95%, 26.61% and 31.19% for very small, small, medium, large and very large drops respectively, which was considered consistent with the relatively high rainfall intensity generated by the test rig.

Select this Article		Design and Testing of a Flow Measurement System for an Urban Sewage Drain S. K. Gupta, Vijay P. Singh, F. ASCE, and V. B. Mishra Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000445 Posted ahead of print 4 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract A flow measuring system was developed to measure the flow rate of a river called Assi, a tributary to River Ganges in the city of Varanasi, India. The Assi River carries a huge quantity of sewage water, and thus serves as large sewerage drain for the city. A sewage treatment plant that is under consideration to treat the waste water discharge into the Ganges needed empirical flow data to establish its design capacity. This gave rise to the installation of a flow measuring system. The distinctive features of the measuring system, which has potential for application to other areas around the world, are discussed.

Select this Article		A Real‐Time Model for Optimal Water Allocation in Irrigation Systems during Droughts M. Delavar, M. Moghadasi, and S. Morid Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000440 Posted ahead of print 2 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract The agricultural sector is the main victim of drought and efficient water planning and management is the best strategy to reduce drought pressures on this sector. One operational approach is the application of real‐time models to help water managers decide on mitigation measures such as deficient irrigation or reducing cropped areas using the new incoming information (e.g. recorded inflows, precipitation, etc). The present paper introduces a real‐time modeling approach for optimal water allocation during drought. The model includes two main components: forecasting and optimization modules. The forecasting module uses a recurrent neural network technique to forecast annual inflows that is updated as the monthly climate and hydrological data are introduced to the model. The optimization module allocates water among the irrigation units and their crops by considering growing stage, sensitivity to water stress at different stages, available/forecasted water and previous decisions about water release. The model was tested for the 1999 drought of Zayandeh Rud irrigation system. It was shown that traditional operating procedures produced 42% loss while the proposed method would have reduced loss to 12%.

Select this Article		A Water Budget Calculator Created for Residential Urban Landscapes in Albuquerque, New Mexico Salman D. Al‐Kofahi, Dawn M. VanLeeuwen, Zohrab A. Samani, and Rolston St. Hilaire Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000439 Posted ahead of print 1 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract The current methods used to calculate urban landscape water budgets are limited because they lack site specificity. The objective of this study was to create a landscape water budget web interface based on ground‐proofed information such as plant coefficients (K_s), vegetation components, and reference evapotranspiration (ET_o). Using Albuquerque, New Mexico as the base city, mixed landscape and monthly turf grass coefficients for each zip code in Albuquerque were developed. The spatial variability of zip code ET_o and ET_o weather anomalies was assessed because of their potential impact on water budgets. Evapotranspiration varied among zip codes, months, and El Niño Southern Oscillation (ENSO) phases. To improve the water budget estimate, the interface accounts for spatial and temporal variability of the monthly, historical (monthly and yearly), and the ENSO phases ET_o. Because non‐turf landscape plant K_s's were unavailable for Albuquerque, we developed a Region Match Analysis to transfer non‐turf plant K_s's from the most similar California climate region to Albuquerque. The interface allows users to input an address and view its image. Users can digitize a site image and calculate the water budget based on either total vegetated areas, areas of trees, shrubs, and grass, or areas of specific plant species. The water budget calculation based on the developed approaches showed a reduction in the estimated water budget compared with the common water budget approach. The web interface can be utilized as a planning tool to estimate water budgets for new developments, irrigation scheduling, and planning for ordinances and policies. The web interface uses improved methods to calculate water budgets and possesses an enhanced potential to provide accurate water budgets.

Select this Article		Characteristics of Flow over Rectangular Sharp‐Crested Side Weirs Sara Bagheri and Manouchehr Heidarpour Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000433 Posted ahead of print 16 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract In this study, water flow over rectangular sharp‐crested side weirs of various heights and widths was investigated. The distribution of the three‐dimensional velocity over the crest and in the vicinity of the side weir was obtained using an acoustic Doppler velocity meter (ADV). The structure of each component of velocity was examined separately. The velocity distributions showed that longitudinal velocity peaks near the beginning of the side weir, while velocity in the direction of spill flow is highest at the end of the weir. The observed values of vertical velocity showed that the direction of flow near the crest is upward, but at the highest depths, the flow direction is reversed and a downward flow is generated near the water surface. Analysis of the velocity profiles indicated that the local discharge increased along the crest of the weir; local discharge also increased as the relative width of the weir decreased. Since the angle of the spilling jet (ϕ) plays a large role in shaping the hydraulic characteristics of the side structure, variation in this angle was investigated and an expression for estimating of ϕ was developed.

Select this Article		A Cost Comparison of Conventional Gray Combined Sewer Overflow Control Infrastructure versus a Green/Gray Combination Jeffrey P. Cohen, Richard Field, Anthony N. Tafuri, and Michael A. Ports Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000432 Posted ahead of print 11 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract This paper outlines a life‐cycle cost analysis comparing a green (rain gardens) and gray (tunnels) infrastructure combination to a gray‐only option to control combined sewer overflow in the Turkey Creek Combined Sewer Overflow Basin, in Kansas City, MO. The area of this Basin is 2,248 ha (5,554 acres). A set of spreadsheets was developed upon which this life‐cycle cost analysis is based. The spreadsheets allow the user to vary the length and/or the diameter of the tunnels. The spreadsheets calculate the additional number of rain gardens that would be needed to handle a given amount of stormwater when the tunnel sizes are reduced. The difference in life‐cycle costs between the green/gray and gray‐only alternatives is calculated. For a range of options for the number of rain gardens, the green/gray combined alternative is more cost effective than the gray‐only option. The potential present worth of the cost savings for the 50 year expected lifespan of both the gray and green infrastructure could reach as much as $35 million for the Turkey Creek Basin.

Select this Article		Effect of Topographic Data Accuracy on Water Storage Environmental Service and Associated Hydrological Attributes in South Florida Alphonce C. Guzha and Sanjay Shukla Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000430 Posted ahead of print 10 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract The effects of digital elevation model (DEM) accuracy on terrain attributes and water storage were evaluated by comparing a standard 10m USGS DEM and a 10m DEM derived from Light Detection and Ranging (LIDAR) data, on a ranchland that is participating in a water storage environmental services program in South Florida. Elevation differences between the two DEMs ranged from ‐0.73 m to 1.6 m with a low (31%) correlation. Frequency analysis showed that 64% of the grids in study area had elevation differences of 0.8 m or greater. Spatial distribution of wetlands and ditches were better represented by the LIDAR than the USGS DEM. Surface water storage in the study area and an isolated wetland was 49% and 21% more, respectively, for the USGS DEM than LIDAR DEM in wet seasons. In dry seasons, the LIDAR DEM resulted in 28% higher storage than the USGS DEM. Annually, the USGS DEM resulted in an average 44% more storage than LIDAR DEM. For a major rainstorm in 2008, the USGS showed 92% inundation of the study area and 44% for the LIDAR DEM. In a selected wetland, the USGS DEM resulted in an average 23% higher annual water storage than LIDAR DEM. In two sub watersheds in the study area, USGS DEM resulted in an average 40% more pasture inundation than LIDAR DEM. Results show the importance of topographic data accuracy in quantified water storage and design of water control structures in water storage environmental services programs.

Select this Article		Irrigation Patterns and Scheduling of a Telecontrolled Irrigation District in North‐Eastern Spain T. Stambouli, N. Zapata, and J. M. Faci Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000429 Posted ahead of print 10 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract Over the last ten years, telecontrol systems have been incorporated into the majority of modern collective pressurized irrigation networks in Spain. This type of infrastructure provides many opportunities for irrigation management but actually, in Spain, is only used for standardized network operations. The Candasnos irrigation district (CID), located in northeastern Spain, is equipped with this system, and contains a variety of different pressurized systems. Telecontrol data and crop water requirements were used to analyze the evolution of irrigation performance (SIPI) of maize, alfalfa and stone fruits. Irrigation guidelines for stone fruit were analyzed and compared to those of standard and regulated deficit irrigation (RDI) irrigation strategies. Ten solid set irrigation systems were monitored to determine on‐farm irrigation patterns. The average SIPI of maize, alfalfa and peach was 83%, 107% and 123%, respectively. The average SIPI showed a high irrigation performance, but the spatial and temporal variability of SIPI showed possibilities for improvement. Deficit irrigation practices were conducted on peach trees, but not adjusted to the recommended RDI strategy. The results of plot monitoring showed crop differences on irrigation time per event (1–1.5 h in maize and 2–3 h in alfalfa) and on time interval between irrigation (larger in alfalfa than in maize). The short and frequent irrigation timing for corn crop could be a disadvantageous practice since it yielded high evaporation losses from crop intercepted water. Two irrigation patterns were established at the CID: the first was characterized by structured irrigation schedules and the second was characterized by weekly changes in the irrigation schedule. The second pattern was more commonly employed in solid set systems than in those with pivots. The analysis of telecontrol data following this methodology could be easily implemented in the daily routines of the district office to improve irrigation management at the plot level. Further, telecontrol data can be an important tool for promoting and facilitating regulated deficit irrigation strategies in stone fruits.

Select this Article		Testing of Micro‐Hydropower Generation from a Sprinkler Irrigation System Tamer Bagatur, Ph.D. Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000428 Posted ahead of print 9 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract Sprinkler irrigation is one of the advanced water‐saving irrigation technology. It has a huge effect for the development of agriculture. Sprinklers are designed to rotate in a circle. In practice, sprinklers can be also used to generate electric power by attaching a generator (dynamo) to its rotating head. Thus, the sprinklers are to be converted into a turbine. Hydropower generation from a sprinkler system is theoretically discussed in text books on fluid mechanics. Therefore, the aim of this paper is to evaluate theoretical considerations and experimental results of hydropower generation from a sprinkler system. In this study, hydropower generation from a sprinkler system is simply tested with the practical application. In result of test, sprinkler irrigation device is capable for hydropower generation. Electrical energy can be produced using sprinkler devices. Hence, generated energy can be used for energy requirements (e.q., remote‐controlled electric sprinkler, lighting and other uses). If sprinkler devices are technological redesigned for both irrigation and power generation, they will generate low‐cost electricity for energy requirements. Also, hydropower can be produced from sprinkler head series in centre pivot sprinkler irrigation type.

Select this Article		Estimation of Border Strip Soil Hydraulic Parameters Shobha Ram, K. S. Hari Prasad, Ajai Gairola, M. K. Jose, and M. K. Trivedi Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000398 Posted ahead of print 11 July 2011 Full Text: \| Download PDF
	+ -	Show Abstract The inverse problem of determining soil hydraulic parameters (Saturated hydraulic conductivity and water retention parameters) of border strip irrigation from irrigation event data is analyzed. The inverse problem is solved using Sequential Unconstrained Minimization Technique. The forward problem involves the solution of coupled Saint Venant's equation governing overland flow and Richards equation governing subsurface flow. Saint Venant's equations are solved using MacCormack scheme based finite difference method while the Richards equation is solved using a mass conservative fully implicit finite difference method. Field experiments are conducted on two border strips to obtain surface and subsurface irrigation data such as irrigation advance, recession, flow depth and soil moisture content. The soil hydraulic parameters, i.e., saturated hydraulic conductivity and soil retention parameters are estimated by minimizing the deviations between the model predicted and field observed irrigation data. The results indicate that defining the objective function in terms of flow depths results in the optimization converging to the true values as compared to the use of irrigation advance data. Further, it is observed that starting the initial guess as under estimated results in the least number of iterations for the optimization algorithm to converge to the true values. It is also observed that simultaneous estimation of all the three soil hydraulic parameters is not possible even with the inclusion of sub surface moisture content data in the objective function.

Select this Article		Experimental Studies on Flow over Labyrinth Weir B. V. Khode, A. R. Tembhurkar, P. D. Porey, and R. N. Ingle Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000336 Posted ahead of print 12 January 2011 Full Text: \| Download PDF
	+ -	Show Abstract Labyrinth spillway is the effective and economical solution to increase the discharge by increasing the spillway crest length without an associated increase in structure width. Use of labyrinth spillway is particularly suited to sites where the spillway width and upstream water surface are limited and larger discharging capacities are required. Recently, its use is found to be attractive solution for upgrading existing development to satisfy more demanding design flood criteria in the limited waterway. The existing spillway is overcoming its earlier limitations of their unusual shape and other complicated flow patterns. Continued efforts are being focused towards development of design curves with different shapes and configurations. The present research mainly aims at evaluating various characteristics of flow‐over labyrinth weir by conducting experimentations at wider range of values for important parameters. This paper deals with experimental study of flow over labyrinth weir for variation of side wall angles (α) from 6° to 30°.

Select this Article		A Two‐Dimensional Numerical Model of Basin Irrigation Based on a Hybrid Numerical Method Shaohui Zhang, Di Xu, and Yinong Li Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000303 Posted ahead of print 19 October 2010 Full Text: \| Download PDF
	+ -	Show Abstract A numerical model of basin irrigation flow is a useful tool in the design and evaluation of surface irrigation systems. A two‐dimensional complete hydrodynamic numerical model of basin irrigation was established by using the time‐space hybrid numerical method. Differences in stability, convergence, precision, and efficiency of the two‐dimensional model were analyzed and compared between the hybrid numerical method proposed here and the Roe finite‐volume method. At the same time, the computational performance and simulation effects were validated based on the results of typical basin irrigation tests. The results show that the hybrid numerical method provides better numerical stability and convergence with little water quantity‐balance and average relative errors than does the Roe finite‐volume method. The computational efficiency is about three times higher under the same measurement circumstances. The proposed model of basin irrigation can increase computational stability and convergence, can improve computational precision and efficiency, and can provide a good numerical simulation tool for the design and evaluation of basin irrigation systems.

Select this Article		Soil Moisture Measurements: A Comparison of Instrumentation Performances Ventura Francesca, Facini Osvaldo, Piana Stefano, and Rossi Pisa Paola Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000130 Posted ahead of print 3 July 2009 Full Text: \| Download PDF
	+ -	Show Abstract It has long been recognized that reliable, robust and automated instrumentation for the measurement of soil moisture content can be extremely useful, if not essential, in hydrological, environmental and agricultural applications. A number of automated techniques for point measurement of soil water content have been developed to operational level over the past few decades. While each of those techniques has been individually calibrated by the gravimetric method, typically under laboratory conditions, there have been few studies that made a direct comparison between the various techniques, particularly under field conditions. This paper compares ECH₂O probes, EC‐5 (both sensors based on capacitance measurements, developed by Decagon Devices) and Time Domain Reflectometer sensors (CS616 Campbell Scientific Water Content Reflectometer), with gravimetric data and with each other, under field conditions. Data were collected during two field experiments characterized by different soils and a wide range of soil moistures, resulting from an irrigation/drying cycle. Results show that all the tested probes give acceptable results after being calibrated in the field. The capacitive sensors can be used in each type of soil with the same calibration equation, independently from depth, with Root Mean Square Error (RMSE) ranging between 2.5 % and 3.6 %. TDR probes showed a dependence on depth but a lower RMSE (1.6 %).

Select this Article		Aquifer Parameter Estimation for a Constant‐Flux Test Performed in a Radial Two‐Zone Aquifer Hund‐Der Yeh, Chun‐Hao Chang, and Yen‐Ju Chen Journal of Irrigation and Drainage Engineering doi:http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000020 Posted ahead of print 26 January 2009 Full Text: \| Download PDF
	+ -	Show Abstract A patchy aquifer or an aquifer with a finite thickness skin can be considered as a radial two‐zone aquifer system, which can be characterized by five parameters, i.e., the thickness of the first zone and four aquifer parameters including the transmissivity and storage coefficient for each of the first and second zones. This paper proposes an approach based on an analytical solution of a constant‐flux pumping in a confined two‐zone aquifer and the simulated annealing algorithm to determine the five parameters simultaneously. The estimated results for the five parameters are fairly good even assuming the aquifer as a single‐zone system at the beginning of the data analysis. The estimated results indicate that the first‐zone parameters are much more difficult to accurately identify than the second‐zone parameters due to insufficient early‐time data and high correlation of the sensitivities among the first‐zone parameters. However, the problem of inaccurate results obtained at the first‐zone can be significantly improved if more densely temporal drawdown measurements are used.