Journal of Irrigation and Drainage Engineering

Knowledge of spatiotemporal distribution of evapotranspiration (ET) on large scales, as quantified by satellite remote sensing techniques, can provide important information on a variety of water resources issues such as evaluating water distributions, water use by different land surfaces, water allocations, water rights, consumptive water use and planning, and better management of ground and surface water resources. The objective of this study was to assess the operational characteristics and performance of the surface energy balance algorithm for land (SEBAL) model for estimating crop ET $\left({\mathrm{ET}}_c\right)$ and other energy balance components, and mapping spatial distribution and seasonal variation of ${\mathrm{ET}}_c$ on a large scale in south-central Nebraska climatic conditions. A total of seven cloud free Landsat Thematic Mapper (TM)/Enhanced Thematic Mapper (ETM) satellite images (May 19, June 20, July 22, August 7, September 8, September 16, and October 18, 2005) were processed to generate ${\mathrm{ET}}_c$ maps and estimate surface energy fluxes. Predictions from the SEBAL model were compared with the Bowen ratio energy balance system (BREBS)-measured fluxes on an instantaneous and daily basis. The ${\mathrm{ET}}_c$ maps generated by the model for seven Landsat overpass days showed a very good progression of ${\mathrm{ET}}_c$ with time during the growing season in 2005 as the surface conditions continuously changed. The predictions for some surface energy fluxes were very good. Overall, a very good correlation was found between the BREBS-measured and SEBAL-estimated ${\mathrm{ET}}_c$ with a good $r^2$ of 0.73 and a root-mean-square difference (RMSD) of $1.04\mathrm{mm}{\mathrm{day}}^{-1}$ . The estimated ${\mathrm{ET}}_c$ was within 5% of the measured ${\mathrm{ET}}_c$ . The model was able to predict growing season (from emergence to physiological maturity) cumulative daily corn ET reasonable well within 5% of the BREBS-measured values. The model overestimated the surface albedo by about 26% with a RMSD of 0.05. The difference between the measured and predicted albedo was the greatest on May 19, early in the growing season before the full canopy cover. The second largest difference between the two albedo values was on October 18, a day after harvest. The model significantly under predicted soil heat flux with a large RMSD of $80\mathrm{W}{\mathrm{m}}^{-2}$ and most of the underestimation occurred in the late growing season. Local calibration of soil heat flux significantly improved the agreement between the measured and predicted values. Furthermore, the sensible heat flux was underestimated between September 20 (after physiological maturity) and October 18 (a day after harvest). While our results showed that SEBAL can be a viable tool for generating ${\mathrm{ET}}_c$ maps to assess and quantify spatiotemporal distribution of ET on large scales as well as estimating surface energy fluxes, its operational assessment for estimating sensible heat flux and ${\mathrm{ET}}_c$ , especially during the drier periods for different surfaces, needs further development.

A center pivot was completely automated using the temperature-time-threshold method of irrigation scheduling. An array of infrared thermometers was mounted on the center pivot, and these were used to remotely determine the crop leaf temperature as an indicator of crop water stress. We describe methods used to automatically collect and analyze the canopy temperature data and control the moving irrigation system based on the data analysis. Automatic irrigation treatments were compared with manually scheduled irrigation treatments under the same center pivot during the growing seasons of 2004 and 2005. Manual irrigations were scheduled on a weekly basis using the neutron probe to determine the profile water content and the amount of water needed to replenish the profile to field capacity. In both years, there was no significant difference between manual and automatic treatments in soybean water use efficiency or irrigation water use efficiency. The automatic irrigation system has the potential to simplify management, while maintaining the yields of intensely managed irrigation.

Emitter pressures and flow rates were systematically and extensively sampled in one drip and one microspray field. The data distributions are presented. The accuracy of rapid (limited samples) evaluation pressure sampling procedures was found to be quite good if the pressure distribution was systematic, but erroneous if the pressure distribution throughout a field was random. A simple mathematical combination of two nonuniformity components (due to pressure differences, and other causes of flow variation) provided a better estimate of overall system distribution uniformity than more complex mathematics.

Emitter clogging is the most annoying problem that restrains the development of drip irrigation technologies, but so far, there have been no effective evaluation methods for the anticlogging performance of drip emitters. In this study, a kind of short-cycle experiment was conducted in the laboratory by mixing sands with various concentrates and particle sizes in irrigation water. Through these tests, the clogging rates that quantitatively represent the clogging status of drip emitters in various experimental conditions were obtained, as well as the variation rules of emitter discharges. The statistical calculation results indicated that the anticlogging performance of predepositing drippers was better than round-flow drip tapes, but less than eddy drip arrows. The discharges of every emitter tested differed from each other and most were lower than nominal discharge rates. However, a few emitters had a contrary result. An important modification had been done for the Christiansen uniformity coefficient to accurately evaluate irrigation uniformity and the clogging status of drip emitters. As a result, a new method of rapid evaluation for the anticlogging performance of drip emitters was proposed.

The paper reviews several methods to convert discharge into gate opening. A control algorithm for one or several reaches of an irrigation canal sometimes uses a discharge as the control action variable even though the device to be manipulated is a gate or a weir. In this case a slave controller has to convert the discharge into a gate opening or a sill elevation in the case of a weir. This is usually done by inverting the static relation between discharge and gate opening. An improved method can be based on the characteristics theory to estimate the deviations of the water levels. However, both methods underestimate the gate opening deviations required to deliver a desired discharge deviation, because water levels vary continuously over time when the gate is operated. The paper proposes a method to take into account this dynamic behavior of the pool-gate interaction by using a simple linear model for the pools’ dynamics, the integer delay zero model. The proposed method enables us to better estimate the gate opening necessary to get a desired average discharge. The method is evaluated in simulation and on a gate of the Gignac Canal, located in the South of France. A dimensionless analysis of the problem is finally performed to evaluate the methods’ applicability.

The article proposes a mathematical model of an automatic upstream water level control gate designed to operate under free and submerged flow conditions, called the Vlugter gate. This automatic gate controls the upstream level close to a design level, using a counterweight to compensate for the hydraulic pressure on the gate. The proposed gate model is an extension of an existing model for free flow conditions (Begemann gate) to submerged conditions. Submergence effects are introduced both in the discharge law and the equilibrium law. The mathematical model is validated on experimental data from two small-scale gates and on data from literature, in order to show the ability of the model to simulate the behavior of gates of various dimensions.

In irrigation basins the decrease in the gradient of the water-surface elevation following inflow cutoff often leads to reduced rate of convergence, increased computational time, and reduced robustness of the numerical solutions of the recession phase. As the water surface levels off, the underlying physical problem simplifies, thus allowing the use of highly accurate yet simple alternate solutions to the full-numerical solution of the zero-inertia equations. For level basins, the simplification involves treating the stream as a static pool, in which water level only falls in response to infiltration. Graded basins may require partitioning the stream into a flowing and static pool, before water-surface eventually levels off over the entire stream length. Implementation of these solutions enhances computational efficiency and robustness of surface irrigation models without a concomitant loss of accuracy. This paper discusses numerical problems related to the recession phase computation in basins and proposes simplified and robust, yet highly accurate solutions. A comparison of the recession trajectories and final infiltration profiles predicted by the full-numerical solution of the zero-inertia equations, obtained by using double-precision floating-point arithmetic, and the simplified alternate solutions, which is robust enough to be implemented over a range of hardware–software capabilities, show that the two approaches yield essentially identical results. Finally, the general validity of the proposed solutions is tested by comparing predictions of recession trajectories and infiltration profiles with those obtained using a surface irrigation hydraulic model, SRFR.

An important objective of a microirrigation system is to determine the proper operating inlet pressure head, ensuring the desired level of water application uniformity as well as the allowable pressure head variation along the multioutlet pipeline. This paper offers, simple, direct, but sufficiently accurate, relationships incorporating different microirrigation uniformity parameters, such as Christiansen uniformity coefficient, coefficient of variation of emitter discharge, and allowable pressure head variation, to determine the operating inlet pressure head (i.e., pressure head and outflow profiles) for multioutlet plastic pipelines. In this analysis some mathematical expressions were deduced to relate three uniformity parameters; then the operating inlet pressure head is simply reformulated by taking into account a multiplying factor $\alpha$ to the required average outlet pressure head, in terms of three uniformity parameters. Resulting, the influence of different uniform pipe slopes on the water application uniformity and the operating inlet pressure head for various emitter discharge exponents, was evaluated. In addition, to cover various design combinations an extensive comparison between the proposed equations and those of the previous studies was also presented. Examination of the results from this research indicated that, the performance of the proposed technique is sufficient in comparison to those of the recent analytical and numerical procedures.

The need exists to develop a method that can quantitatively measure water interception from plant shoots. This paper describes a new method for measuring canopy water interception. Corn (Zea Mays L.) was grown in $13\mathrm{L}$ buckets containing Valentine fine sand (Mixed, mesic Typic Ustipsamment) under a climate-controlled growth chamber. Plants were taken out of the growth chamber for $2–3\mathrm{h}$ periods for measurements of shoot water interception in a hydraulic laboratory equipped with an Accupulse system suspended from the ceiling that was used to wet the corn shoots at growth stages V7–V13. A lightweight, movable framework was placed around a balance, and buckets containing corn plants were placed on the scale one container at a time. Water was applied until all shoot surfaces were wet and runoff from the leaves and stalk surfaces could be observed. The weighing method for shoot water interception was tested by using the balance to instantaneously measure shoot water interception during application of water and after plant surface runoff ceased. The balance, bucket, and soil surface were covered with plastic to protect them from water, so only the shoots were wet. Interception by the shoot of corn ranged from $31\text{to}47\mathrm{mL}{\text{shoot}}^{-1}$ . These values were much smaller than previous values reported in the literature. The average coefficient of variation was 9.2% for two studies, which was much lower than previously accepted methods. This study suggests that the weighing method for shoot water interception can be used to quantitatively and more accurately measure water intercepted by corn shoots. The weighing intercepted method values presented in this paper are low and suggest that previous interception methods overestimated the interception values.

Currently used dielectric spectroscopy methods for measuring soil water contents are highly susceptible to their electrical conductivities. Some of the existing methods are double-plate capacitance sensors. A novel technique based on the use of fringing field sensors for the content detection is presented in our work, which is able to perform real-time capacitance measurements, and process recorded data to obtain the given parameters of interest. A modulated circuit and data acquisition system are designed to meet practical application requirements, and high sensitivity of the proposed sensor to parameter variation was demonstrated based on the experimental data. An approximately linear dependency is observed between water content and measurement voltage when the proportion of water content in the soil sample is below 24% (gravimetric water content), which implies a wide-ranging application of such a technique for real-time measurements of various soil water content under field working conditions where conventional instruments are unavailable.

Based on seven field experiments of pearl millet with nine treatment combinations of tillage and fertilizer nutrients conducted during 2000–2006 in a semiarid inceptisol at Agra, an assessment is made in this paper about sustainability of treatments using rainfall received during the crop growing period and available soil moisture at sowing, 20, 40, and $60\text{days}$ after sowing (DAS) and harvest. Three practices, each of tillage: conventional $\text{tillage}+\text{mechanical}$ weed control, low $\text{tillage}+\text{mechanical}$ weed control, and low $\text{tillage}+\text{mechanical}$ weed $\text{control}+\text{herbicide}$ ; and fertilizer application of $60\mathrm{kg}\mathrm{N}$ $\left[\text{farm}\text{yard}\text{manure}\left(\mathrm{FYM}\right)\right]+40\mathrm{kg}\mathrm{P}∕\mathrm{ha}$ , $30\mathrm{kg}\mathrm{N}$ $\left(\mathrm{FYM}\right)+30\mathrm{kg}\mathrm{N}$ $\left(\text{urea}\right)+40\mathrm{kg}\mathrm{P}∕\mathrm{ha}$ and $60\mathrm{kg}\mathrm{N}$ $\left(\text{urea}\right)+40\mathrm{kg}\mathrm{P}∕\mathrm{ha}$ were tested in the same site over seven years. The F-test indicated significant soil moisture differences on different DAS and also between different tillage treatments. Significant yield differences were found among treatments of tillage and fertilizer and their interaction in all seasons, except 2001 and 2002. Treatment-wise correlation of yield with monthly rainfall received in June–September and available soil moisture on different DAS indicated that September rainfall had a negative and significant correlation with yield attained by tillage and fertilizer treatments. The soil moisture at 20 DAS had a negative and significant correlation with yield under all treatments except conventional $\text{tillage}+\text{mechanical}$ weed control. The soil moisture at 60 DAS and harvest had a positive and significant correlation with yield attained under different tillage and fertilizer treatments. Regression models of yield were calibrated for tillage and fertilizer treatments through monthly rainfall during July–September and soil moisture on different DAS. The predictability of yield improved significantly by inclusion of both rainfall and soil moisture variables in the models compared to either of the two groups of variables. Ranks were assigned to tillage and fertilizer treatments for yield attained in individual years and mean yield, prediction error, and sustainable yield index over years. The study indicated that conventional $\text{tillage}+\text{mechanical}$ weed control among tillage together with $30\mathrm{kg}\mathrm{N}$ $\left(\mathrm{FYM}\right)+30\mathrm{kg}\mathrm{N}$ $\left(\text{urea}\right)+40\mathrm{kg}\mathrm{P}∕\mathrm{ha}$ was superior with a minimum rank sum compared to other treatments. The treatment gave a maximum sustainable yield of $\mathrm{1,683}\mathrm{kg}∕\mathrm{ha}$ with a net return of Rs $\mathrm{5,670}\mathrm{ha}$ , benefit–cost ratio of 1.16, and sustainable yield index of 47.2% under semiarid inceptisols of Agra.

This paper develops a nonlinear programming model to optimally design a settling basin for a small-scale drainage area with a minimum total cost. It is assumed that the shape of the settling basin is rectangular parallelepiped, and it is connected to an open channel at both ends. Therefore, the decision variables include the scales of the settling basin (i.e., length, width, and height) and the scales of the channel (i.e., width and height). The design trap efficiency requirement, which must be greater than or equal to the required one of the considered watershed, makes up the main constraint. Other constraints consist of the upper and lower bounds of the decision variables, the equations for computing the trap efficiency, and the average flow velocity in the settling basin. The objective function is to minimize the total annual cost, which is the sum of the land, capital, and maintenance-operation cost. The developed model is solved by using a genetic algorithm. This model is applied to a subwatershed of the Wu-She Reservoir watershed in central Taiwan. The obtained results effectively demonstrate the applicability and practicability of the model.

A power-law channel section is very versatile. It can model a wide range of familiar man-made or natural channel shapes. However estimating the wetted perimeter of a power-law channel section is difficult. The problem gets complicated further when considering the freeboard in the design process. In this paper, the wetted perimeter is estimated using the isoperimetric theorem which results in a simple and accurate expression for the wetted perimeter that does not lead to discontinuity in the optimal solution. For unconstrained optimum power-law channels, it is shown that the exponent and side slope at the water surface have values of 0.314 and 0.352, respectively, independent of either the maximum side slope or the relative freeboard. The analyses have also shown that the most hydraulically efficient power-law channel sections come closest to the semicircle. They tend to be U shaped and narrow with small relative freeboard $(⩽0.30)$ . A design procedure and two design charts are presented together with two illustrative examples to demonstrate the simplicity of the method.

Groundwater flow modeling has been used extensively worldwide with varying degrees of success. The ability to predict the groundwater flow is critical in planning and implementing groundwater development projects under increasing demand for fresh water resources. This paper presents the simulation of the aquifer system for planning the groundwater development of Varada basin, Karnataka, India using the Galerkin finite-element method. The government of Karnataka State, India is implementing the World Bank assisted project, “Jal Nirmal” for a sustainable development of the region, thereby ensuring a safe supply of drinking water to the northern districts of the state. Varada basin is one of the beneficiaries of the project in Haveri district. Field tests carried out in the study area indicate that the region is predominantly a confined aquifer with transmissivity and storage coefficients ranging from $5.787\times {10}^{-6}{\mathrm{m}}^2∕\mathrm{s}$ $(0.500{\mathrm{m}}^2∕\mathrm{day})$ to $4.213\times {10}^{-3}{\mathrm{m}}^2∕\mathrm{s}$ $(3.640\times {10}^2{\mathrm{m}}^2∕\mathrm{day})$ and $0.011–0.001\times {10}^{-2}$ , respectively. This study mainly emphasizes the spatial and temporal variability of groundwater potential under different developmental scenarios. The model predictions were reasonably good with correlation coefficients ranging from 0.78 to 0.91 with the root mean square error of about 0.46–0.78 during calibration and validation. The stated accuracies are based on comparisons between measured and calculated heads. The outcome of the study would be a useful input for the conjunctive use of surface water and groundwater planning for the sustainable development of the region.

Well injection replenishes depleting water levels in a well field. Observation well water levels some distance away from the injection well are the indicators of the success of a well injection program. Simulation of the observation well response, located a few tens of meters from the injection well, is likely to be affected by the effects of nonhomogeneous medium, inclined initial water table, and aquifer clogging. Existing algorithms, such as the U.S. Geological Survey groundwater flow software MODFLOW, are capable of handling the first two conditions, whereas time-dependent clogging effects are yet to be introduced in the groundwater flow models. Elsewhere, aquifer clogging is extensively researched in theory of filtration; scope for its application in a well field is a potential research problem. In the present paper, coupling of one such filtration theory to MODFLOW is introduced. Simulation of clogging effects during “Hansol” well recharge in the parts of western India is found to be encouraging.

A flooding probability based cost effective design of open channel section has been proposed using freeboard as an additional design variable. The freeboard of the channel is calculated based on the flooding probability value. The proposed model is solved using classical optimization techniques as well as a nondominated sorting genetic algorithm. The results of the model are compared with an earlier reported model to demonstrate its superiority and field applicability.

The existing equation applicable for large diameter wells in confined aquifers is transformed into a convenient form and a set of semilogarithmic diagnostic curves is developed for identifying the aquifer parameters (storage coefficient and transmissivity) from early drawdowns in large diameter wells. A scaled well function is proposed for the diagnostic curves. The aquifer parameters are estimated by matching the diagnostically plotted drawdowns to one of the diagnostic curves by a parallel shift of only one axis. The substantial curvature of the diagnostic curves and shifting of only one axis facilitate matching and reduce subjectivity. The proposed method is an improvement over the existing matching methods. The new method can reliably identify the aquifer parameters from only early drawdowns and would result in a 100-fold saving in time and money. It is hoped that this method would be helpful to field engineers and practitioners.

An approach for incorporating large-diameter wells into MODFLOW is presented. A transformation of transmissivity in the flow field is devised to simulate the well function for a large-diameter wells. Transformations for accounting for the well radius and well storage are also developed. Using these transformations, MODFLOW is used to obtain the drawdowns. It is observed that the flow to a large diameter well can be accurately modeled using the proposed transformations and MODFLOW.