Journal of Irrigation and Drainage Engineering

Published by American Society of Civil Engineers
Print ISSN: 0733-9437
Publications
Initial soil moisture distribution, as simulated for the day of sowing of the Lavalette run  
Observed and simulated advance and recession times for the Flowell-wheel run  
Simulated components of evapotranspiration at x inf = 32.5 m during the entire growing season of the Lavalette run: potential transpiration T P , actual transpiration T A, potential evaporation EP and actual evaporation EA
A physically based seasonal furrow model was developed, which comprises three modules: The one-dimensional surface flow , the two-demensional suvsurface flow, and a crop model. The modeling principle of these modules, their simulatneous coupling, and the solution strategies were described in a companion paper (Wöhling and Shmitz 2007). In the current contribution, we present the model testing with experimental data from five real-scale laboratory experiments [Hubert-Engels Laboratory (HEL)], two field experiments in Kharagpur, Eastern India (KGP), one literature data set [Flowell-wheel (FW) ]and data from three irrigation during a corn growing season in Montpellier., Southern France [Lavalette experiments (LAT)]. The simulated irrigation advance times match well with the observations of the HEL, FW and KGP experiments, which is confirmed by coefficients of determination R2 >>0.99 and coefficients of efficiency Ce > 0.7. Predicted recession times also match with observations of HEL runs, however, the values of R2> 0.9 and Ce >0.6 are lower for predicted recession times as coimpared to predicted advance times. In contrast to other experiments in the study, advance times are under predicted for experiments in France. The established soil hydraulic parameters for this site lead to an underestimation of the actual initial infiltration capability of soil. In the long-term simulation, however, the overall change in soil moisture storage is correctly predicted by the model and calculated yield of 12.8 t/ha is in very good agreement with the observations (12.7 t/ha). We evaluated the sensitivity of the input parameters with regards to predicted advance time and runoff in both a 26.4 m long furrow and a long 360 m long furrow. The analysis reveald that calculated runoff is four to five times more sensitive to the inlet flow rate than to infiltration parameters. Furrow geometry parameters are most sensitive to calculated adavance times in the short furrow with low infiltration opportunity time, whereas the inflow rate and infiltration parameters are more sensitive to calculated advance times in the long furrow with larger infiltration opportunity time.
 
Crop coefficient curves provide simple, reproducible means to estimate crop evapotranspiration (ET) from weather-based reference ET values. The dual crop coefficient sKcd method of the Food and Agricultural Organization of the United States (FAO) Irrigation and Drainage Paper No. 56 (FAO-56) is intended to improve daily simulation of crop ET by considering separately the contribution of evaporation from soil. The dual method utilizes "basal" crop coefficients representing ET from crops having a dry soil surface and separately predicts evaporation from bare soil based on a water balance of the soil surface layer. Three extensions to the evaporation calculation procedure are described here that are intended to improve accuracy when applications warrant the extra complexity. The first extension uses parallel water balances representing the portion of the soil surface wetted by irrigation and precipitation together and the portion wetted by precipitation alone. The second extension uses three "stages" for surface drying and provides for application to deep cracking soils. The third extension predicts the extraction of the transpiration component from the soil surface layer. Sensitivity and analyses and illustrations indicate moderate sensitivity of daily calculated ET to application of the extensions. The dual Kc procedure, although relatively simple computationally and structurally, estimates daily ET as measured by lysimeter relatively well for periods of bare soil and partial and full vegetation cover.
 
For the last three decades, research focused on steep stepped chutes. Few studies considered flat-slope stepped geometries such as stepped storm waterways or culverts. In this study, experiments were conducted in a large, flat stepped chute (~3.4 degrees) based upon a Froude similitude. Three basic flow regimes were observed: nappe flow without hydraulic jump, transition flow, and skimming flow. Detailed air-water flow measurements were conducted. The results allow a complete characterization of the air concentration and bubble count rate distributions, as well as an accurate estimate of the rate of energy dissipation. The flow resistance, expressed in terms of a modified friction slope, was found to be about 2.5 times greater than in smooth-chute flow. A comparison between smooth- and stepped-invert flows shows that greater aeration and larger residence times take place in the latter geometry. The result confirms the air-water mass transfer potential of stepped cascades, even for flat slopes (<5 degrees).
 
Color Long-term average daily ET r to ET o ratios K r values as function of date for each location for calendar year. Each K r value represents average of 8, 22, 15, 20, 16, and 12 years of average values for Bushland, Clay Center, Davis, Gainesville, Phoenix, and Rockport. HPRCC Penman K r values were calculated only for Clay Center, and 1963 J-H K r values were calculated only for Phoenix.
Coordinates, Elevation, and Years Studied for Each Location from Dry to Humid
Color Long-term daily RH min values at each study site. These datasets are provided for comparison with base values of RH min that were used in FAO56 K r calculation procedure Eq. 1 of this study.
Long-Term Monthly Average Climatic Information Including Wind Speed at 2 m U 2 , m s −1 , Maximum and Minimum Air Temperatures T max and T min , °C, Average Relative Humidity RH avg , %, Incoming Solar Radiation R s , MJ m −2 day −1 , and Monthly Total Rainfall Rain, mm for Study Locations
Values for C n and C d in Eq. 2 for Daily Time Step for Grass and Alfalfa-Reference Surfaces ASCE-EWRI 2005
Alfalfa-reference evapotranspiration (ETr) values sometimes need to be converted to grass-reference ET (ETo), or vice versa, to enable crop coefficients developed for one reference surface to be used with the other. However, guidelines to make these conversions are lacking. The objectives of this study were to: (1) develop ETr to ETo ratios (K-r values) for different climatic regions for the growing season and nongrowing (dormant) seasons; and (2) determine the seasonal behavior of K-r values between the locations and in the same location for different seasons. Monthly average K-r values from daily values were developed for Bushland, (Tex.), Clay Center, (Neb.), Davis, (Calif.), Gainesville, (Fla.), Phoenix (Ariz.), and Rockport, (Mo.) for the calendar year and for the growing season (May-September). ETr and ETo values that were used to determine K-r values were calculated by several methods. Methods included the standardized American Society of Civil Engineers Penman-Monteith (ASCE-PM), Food and Agriculture Organization Paper 56 (FAO56) equation (68), 1972 and 1982 Kimberly-Penman, 1963 Jensen-Haise, and the High Plains Regional Climate Center (HPRCC) Penman. The K-r values determined by the same and different methods exhibited substantial variations among locations. For example, the K-r values developed with the ASCE-PM method in July were 1.38, 1.27, 1.32, 1.11, 1.28, and 1.19, for Bushland, Clay Center, Davis, Gainesville, Phoenix, and Rockport, respectively. The variability in the K-r values among locations justifies the need for developing local K-r values because the values did not appear to be transferable among locations. In general, variations in K-r values were less for the growing season than for the calendar year. Average standard deviation between years was maximum 0.13 for the calendar year and maximum 0.10 for the growing season. The ASCE-PM K-r values had less variability among locations than those obtained with other methods. The FAO56 procedure K-r. values had higher variability among locations, especially for areas with low relative humidity and high wind speed. The 1972 Kim-Pen method resulted in the closest K-r values compared with the ASCE-PM method at all locations. Some of the methods, including the ASCE-PM, produced potentially unrealistically high K-r values (e.g., 1.78, 1.80) during the nongrowing season, which could be due to instabilities and uncertainties that exist when estimating ETr and ETo in dormant season since the hypothetical reference conditions are usually not met during this period in most locations. Because simultaneous and direct measurements of the ETr and ETo values rarely exist, it appears that the approach of ETr to ETo ratios calculated with the ASCE-PM method is currently the best approach available to derive K-r values for locations where these measurements are not available. The K-r values developed in this study can be useful for making conversions from ETr to ETo or vice versa, to enable using crop coefficients developed for one reference surface with the other to determine actual crop water use for locations, with similar climatic characteristics of this study, when locally measured K-r values are not available.
 
Location map of Malaprabha Reservoir 
Crop calendar adopted in the command area 
Relative yield of maize in kharif season and sorghum in rabi season for different generations of GA for State 5
Comparison of AET values by GA and LP for kharif season 
Comparison of AET values by GA and LP for rabi season 
This paper presents a genetic algorithm (GA) model for obtaining an optimal operating policy and optimal crop water allocations from an irrigation reservoir. The objective is to maximize the sum of the relative yields from all crops in the irrigated area. The model takes into account reservoir inflow, rainfall on the irrigated area, intraseasonal competition for water among multiple crops, the soil moisture dynamics in each cropped area, the heterogeneous nature of soils, and crop response to the level of irrigation applied. The model is applied to the Malaprabha single-purpose irrigation reservoir in Karnataka State, India. The optimal operating policy obtained using the GA is similar to that obtained by linear programming. This model can be used for optimal utilization of the available water resources of any reservoir system to obtain maximum benefits.
 
This journal article was published in the journal, Journal of Irrigation and Drainage Engineering [© ASCE]. The definitive version is available at: http://cedb.asce.org On irrigation schemes with rotational irrigation systems in semiarid tropics, the existing rules for water allocation are based on applying a fixed depth of water with every irrigation irrespective of the crops, their growth stages and soils on which these crops are grown. However when water resources are scarce, it is necessary to allocate water optimally to different crops grown in the irrigation scheme taking account of different soils in the command area. Allocating water optimally may lead to applying less water to crops than is needed to obtain the maximum yield. In this paper, a three stage approach is proposed for allocating water from a reservoir optimally based on a deficit irrigation approach, using a simulation-optimization model. The allocation results with a deficit irrigation approach are compared for a single crop (wheat) in an irrigation scheme in India, firstly with full irrigation (irrigation to fill the root zone to field capacity) and secondly with the existing rule. The full irrigation with a small irrigation interval was equivalent to adequate irrigation (no stress to the crop). It is found that practising deficit irrigation enables the irrigated area and the total crop production in the irrigation scheme used for the case study to be increased by about 30- 45% and 20-40%, respectively over the existing rule and by 50% and 45%, respectively over the adequate irrigation. Allocation of resources also varied with soil types.
 
Definition sketch of cross section of ditch-drained hillslope aquifer. Sketch is distorted for easy display, but in reality LD 
shows the transient behavior as obtained from Eq. 11 for a 2° hillslope, with D2 m, L100 m, k0.001 m/s, f 0.34, N3 mm/h, H 1 0.5 m, and H 2 1.5 m. The linearization constant p was taken equal to 1/3 as suggested by Brutsaert and Nieber 1977. As can be seen from the water table reaches heights above the ground surface. In practice, this condition would result in overland flow caused by exfiltration of the groundwater and infiltration excess. As overland flow is not described by Eq. 2, its analytical solution cannot describe the actual occuring transient processes. Nevertheless, the steady state solution reveals whether or not the groundwater table will reach the surface. If, on the other hand, we assume the initial water table height to be D2 m in a thicker soil layer e.g. 3 m, see Fig. 2, then the curves predicted by Eq. 11 will reflect the actual transient groundwater table heights. 
Transient behavior of water table for 2° hillslope. Initially, water height in bottom left and upper right ditch was 0.5 and 1.5 m, respectively. At time t0, these heights were changed to 1.5 and 0.5 m. Recharge rate changed at t0 from 1 to 3 mm/h. Arrow indicates evolution of groundwater table. Lines are results of analytical expression; symbols represent numerical approximation 
This paper presents two analytical solutions of the linearized Boussinesq equation for an inclined aquifer, drained by ditches, subjected to a constant recharge rate. These solutions are based on different initial conditions. First, the transient solution is obtained for an initially fully saturated aquifer. Then, an analytical expression is derived for the steady state solution by allowing time to approach infinity. As this solution represents the groundwater table shape more realistically, this water table profile is used as an initial condition in the derivation of the second analytical solution for the groundwater table height, and the in- and outflow into the ditches. The solutions allow the calculation of the transient behavior of the groundwater table, and its ouflow, due to changing percolation rates or water level heights in both ditches.
 
The determination of aquifer parameters is fundamental to groundwater resources assessment. This important topic has received much attention in the literature over many years. Singh (2008) presented a method for determination of parameters for an ideal confined aquifer, based on early drawdown data. The Theis well function (Theis 1935), the topic of interest here, arises as a core part of the analysis. It is, of course, essential that approximations to the Theis well function be robust and accurate so that reliable estimates of aquifer parameters are obtained. Two approximations for the Theis well function were presented by Singh (2008). The purposes of this discussion were (1) to examine these two approximations, in particular their relative error as reported by the author, and (2) to alert readers to an existing, easy-to-calculate approximation to the Theis well function.
 
Irrigated areas in the province of Mendoza, Argentina 
Schematization of the hydrologic system in the SIMGRO model for irrigated areas adapted from Querner 1997
Simulated and measured soil electrical conductivity in the root zone for grapes in an area with deep groundwater levels
Relative evapotranspiration ͑ monthly values ͒ of agricultural crops for an area with deep groundwater levels 
The SIMGRO hydrologic simulation model was extended to include irrigation practice. It could then be used to evaluate the effect of hydrologic changes in an irrigated area in the province of Mendoza, Argentina where, given an average annual rainfall of approximately 200mm , irrigation is crucial for agriculture. A storage dam was recently constructed in the Mendoza River to control the fluctuating river flow and to guarantee that the demand for water is met throughout the year. The dam will impact on parts of the irrigation system where groundwater levels are already high and salinization occurs. To evaluate these changes and possible mitigation measures, two performance indicators that consider groundwater and surface water were used: Relative evapotranspiration and the depleted fraction. Scenario runs revealed that the irrigation water losses from the canals affect the groundwater levels in the downstream part of the irrigated area; an increase in salinity was also revealed
 
The effect of the October 1983 floods in southeastern Arizona, on a previously established generalized envelope for floods expected once in 100 years (gioo). is studied. The design envelope is found to produce more conservative estimates of gioo than individual data sets find. The design envelope for gioo is revised to correct for some longer periods of record now available, and to be consistent with floods on a wider range of drainage area than previously considered. Additional design envelopes for floods expected once in 2 years (Qz) and once in 10 years (Qio) are prepared, and the three envelopes are used to provide conservative estimates of flood frequencies on ungaged watersheds in southeastern Arizona with drainage areas between 0.01 km2and 10,000 km2. A procedure is presented for developing regional flood frequency estimates that could be used in geographically and climatically homogeneous areas.
 
Automated open- and closed-loop control systems can enhance the performance of irrigation delivery systems. This paper examines the response of the canal test cases developed by the ASCE task com- mittee on canal automation algorithms to a particular anticipatory open-loop control technique, gate stroking. The performance of the ideal gate-stroking solution is compared with the performance of an approximate gate- stroking schedule that was generated by imposing practical constraints on the frequency and magnitude of the gate adjustments. Also analyzed were the performance of a nonanticipatory open-loop control scheme and the effect of model parameter uncertainties on the effectiveness of the control. For the test cases, the approximate gate-stroking schedules performed similarly to the ideal schedules. For two of the test cases, delivery perfor- mance was similar with and without anticipation, but was substantially different for the other two tests. The quality of the control degraded as a result of errors in model parameters, particularly in cases with incorrect check gate calibrations and submerged gate flows. Results point out the importance of combining open- and closed-loop control measures to improve the overall effectiveness of the control.
 
Quantifying evapotranspiration (ET) from agricultural fields is important for field water management, water resources planning, and water regulation. Traditionally, ET from agricultural fields has been estimated by multiplying the weather-based reference ET by crop coefficients (Kc) determined according to the crop type and the crop growth stage. Recent development of satellite remote sensing ET models has enabled us to estimate ET and Kc for large populations of fields. This study evaluated the distribution of K c over space and time for a large number of individual fields by crop type using ET maps created by a satellite based energy balance (EB) model. Variation of Kc curves was found to be substantially larger than that for the normalized difference vegetation index because of the impacts of random wetting events on Kc especially during initial and development growth stages. Two traditional Kc curves that are widely used in Idaho for crop management and water rights regulation were compared against the satellite-derived Kc curves. Simple adjustment of the traditional Kc curves by shifting dates for emergence, effective full cover, and termination enabled the traditional curves to better fit Kc curves as determined by the EB model. Applicability of the presented techniques in humid regions having higher chances of cloudy dates was discussed.
 
A method for assessing the impacts on streamflow resulting from withdrawing water from the stream channel or from shallow wells adjacent to the stream for irrigation is presented. Assessment is based on a detailed study at a base station on the stream. Monthly irrigation demands are estimated and added to measured streamflow to determine the natural streamflow. The natural streamflow is correlated with flow on a nearby watershed to develop an extensive series of monthly flows. The procedure produces probability distributions for average monthly flow for each month of the growing season, for different levels of irrigation usage. The flow distributions include the original variation and the additional variation produced by the irrigation withdrawal. The streamflow information developed can be combined with biological or water quality models to assess the impacts of reduced flow on instream biology, water quality, and treatment requirements of waste discharged to streams.
 
Some two-dozen methods have been proposed in the literature for estimating an infiltration function from field measurements. These methods vary in their data requirements and analytical rigor, however most assume some functional form of the infiltration equations. In this paper, if is shown that the form of infiltration and roughness equations can cause errors in the estimation of actual conditions. For example, assumptions regarding the influence of wetted perimeter on furrow infiltration can result in inappropriate infiltration equations and parameters. Also, the Manning n has been shown to vary with time during an irrigation event as the soil is smoothed by the flowing water. Thus estimates of Manning n based on the advance curve may vary substantially from those based on measured water depths. Inappropriate selection of equations or parameter values for infiltration or roughness can lead to unrealistic parameter values for the other. The estimated parameters from evaluation of a measured irrigation event usually give reasonable estimates of actual performance. However, extrapolation to future irrigation events, particularly with a different application depth or flow rate, can lead to inappropriate recommendations.
 
Simulation studies have demonstrated that automatic control of canals is more effective when feedforward scheduling, or routing of know demand changes, is combined with centralized, automatic, distant, downstream water level control. In practice, few canals use this approach. To help further develop and test this strategy, the writers developed SacMan, or Software for Automatic Canal Management. The software was tested on the WM lateral of the Maricopa Stanfield Irrigation and Drainage District, Stanfield, Arizona. Initial testing was done during 2002 and 2003. In 2004, SacMan was used to operate the canal nearly continuously for a period of 30 days. Tests were conducted during normal operations, during which more than 50 delivery changes to users were scheduled and implemented with SacMan. In addition, SacMan responded to unscheduled changes such as emergency shut off and power outages that reduced well flow that had been pumping into the canal. Additional “manufactured” tests were conducted to compare different control methods. This paper describes the overall SacMan control scheme and presents a summary of the tests conducted and typical results. Companion papers examine the results of these tests in more detail.
 
Simulation models for unsteady open channel flows have been commercially available for more than 2 decades. Most of these models are now available for personal computers and can be used to study the control of irrigation canals. Studies on automatic control methods and algorithms have been performed on at least half a dozen of the available unsteady-flow simulation models. Although, many of these automation studies have been conducted by the institution that created the simulation model, these simulation models were not created with automatic gate control in mind, and thus one has to be intimately familiar with the source code in order to implement sophisticated control features. Three commercially available unsteady-flow simulation software packages that allow automatic control of gates based on algorithms written by users are: CanalCAD from the Univ. of Iowa, Hydraulics Lab; Mike 11 version 3.2 from the Danish Hydraulic Institute; and Sobek from Delft Hydraulics. In this paper, we describe the various features of these unsteady-flow simulation packages and how they interface to control engineering software/code. There are a number of tradeoffs between simplicity and functionality. All these models present difficulties and have limitations. The hope is to provide guidance on the next generation of unsteady-flow canal simulation models so that control functions can be routinely applied.
 
The paper presents a method to automatically tune decentralized Proportional Integral (PI) controllers for an irrigation canal pool. The Auto Tune Variation (ATV) method is based on a relay experiment, which leads to small amplitude oscillations of the canal pool. The test signal is automatically generated by a relay inserted in the feedback loop. The method automatically estimates the ultimate gain and ultimate frequency of the pool, which can be used to tune P, PI or PID controllers. This method does not require advanced automatic control knowledge and is implemented in SIC software, developed by Cemagref, which also incorporates a SCADA module for real-time control. The ATV method is evaluated by simulations and experiments on a real irrigation canal located in the South of France, for local upstream, local downstream and distant downstream controller tuning.
 
The feasibility of automatically controlling water levels and deliveries on the Salt River Project (SRP) canal system through computer-based algorithms is being investigated. The proposed control system automates and enhances functions already performed by SRP operators, namely feedforward routing of scheduled demand changes, feedback control of downstream water levels, and flow control at check structures. Performance of the control system was tested with unsteady flow simulation. Test scenarios were defined by the operators for a 30 km, four-pool canal reach. The tests considered the effect of imperfect knowledge of check gate head-discharge relationships. The combined feedback-feedforward controller easily kept water level deviations close to the target when dealing with routine, scheduled flow changes. Those same routine changes, when unscheduled, were handled effectively by the feedback controller alone. The combined system had greater difficulty in dealing with large demand changes, especially if unscheduled. Because feedback flow changes are computed independently of feedforward changes, the feedback controller tends to counteract feedforward control actions. The effect is unimportant when dealing with routine flow changes but is more significant when dealing with large changes, especially in cases where the demand change cannot be fully anticipated.
 
Canopy temperatures of three replicate plots on corn in 1999 (Evett et al, 2000) compared with air temperature. Also shown are horizontal bars drawn at the threshold temperature of 28 °C and over the length of the threshold time (240-min). Because the canopy was above the threshold temperature for more than the threshold time on day 234, irrigation occurred in the evening of that day, but not in the evening of day 235.
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.
 
The temporal distribution of an irrigation water delivery and demand ratio was used to analyze the performance of an irrigation water delivery system in the Bhakra Canal Command in India. A high degree of mismatch was found to exist between water demand and supply. Based on historical canal deliveries, agroclimatic data, and crop production with dated inputs, yields of wheat, a major irrigated crop of the region, were simulated over a period of 20 years. It was found that crop production was constrained by 34% (20-year average) due to unfavorable water delivery characteristics. An evaluation was made of introducing auxiliary storage at the farm outlet level to modify the water delivery schedule. Based on the increase in crop yield due to improved distribution of water supply delivery and the cost of auxiliary storage (including the cost of pumping), it was found that auxiliary storage could be used to considerable economic advantage.
 
Engineering analysis of surface irrigation systems is predicated on reasonably accurate estimates of a field's infiltration properties. Optimal estimation methods pose multiple volume balance equations at various stages of an irrigation event and are assumed to produce the most accurate results among volume balance based procedures. They have the disadvantage of requiring surface volume determinations, which may be difficult to obtain in practice under many field conditions. This study contrasts infiltration solutions from optimal and a simpler postirrigation volume balance method and examines the implications of those solutions on the performance of management strategies with zero-slope and low-gradient basins. With those types of systems, there is little benefit in using optimization over postirrigation volume balance due to the nonuniqueness of solutions and uncertainties of inputs required by the estimation procedures. In addition, system hydraulic characteristics mitigate the insensitivity of the distribution uniformity to reasonable variations in infiltration characteristics from those assumed in the analysis. For the type of systems considered here, management can be optimized based on time needed to infiltrate a target depth, even if the infiltration function parameters are uncertain.
 
A 0.20-ha (0.5-acre) recharge basin was tested for conserving storm runoff that collected in a 16-ha (40-acre) playa in the Southern High Plains. The basin was constructed by removing 1.2 m (4 ft) of soil to expose permeable sediments. Turbid water was pumped from the playa to the basin during eight tests over a 7-yr interval. Average recharge rate during 187 days of flooding was 0.373 m/d (1.22 ft/day). After three recharge tests during the first year, no maintenance was done to the basin bottom. Our research showed that recharge basins could be an effective technique for partially replenishing the depleted Ogallala Aquifer.
 
Chufa, also known as tigernut, is a typical crop in Valencia, Spain, where it is cultivated in ridges with furrow irrigation. This paper examines the effects of the planting strategy (PS) and irrigation system (IS) on yield and irrigation water use efficiency (IWUE) on the basis of the results from a two-year study. The authors analyzed three PS, ridges with a plant row (R) and flat raised beds containing two (B2) or three (B3) plant rows and compared two IS, furrow (FI) and drip irrigation (DI). Irrigation was based on the volumetric soil water content (VSWC), continuously monitored with capacitance sensors. Each irrigation event started when the VSWC in R dropped to 60 or 80% of the field capacity in FI or DI, respectively. Beds and ridges were irrigated simultaneously and for the same duration. There were differences among IS and PS, with DI and B2 obtaining the highest yield. On average, DI produced higher IWUE values than FI; the highest IWUE was obtained in R for DI, and the lowest IWUE was obtained in R for FI. Thus, modifications to the PS and the IS in chufa cultivation will increase IWUE and lead to major water savings.
 
Ratio of Critical Flow Depth to Residue Diameter, Critical Rn, T C , F, and Rn, for Selected Residue Materials on Smooth Surface
Ratio of Critical Flow Depth to Residue Diameter, Critical Rn, T C , F t and Rn" for Selected Sites
Regression Equations for F t versus Rn" for Smooth and Sand Surfaces
Conservation tillage systems help to maintain residue materials from the previous crop on the soil surface. The potential for serious erosion may exist if crop residues are removed by overland flow. This study is conducted to identify the hydraulic conditions required to initiate residue movement by overland flow. Corn, cotton, peanut, pine needles, sorghum, sunflower, and wheat residue are placed in a flume on smooth and sand surfaces, and flow is then introduced in progressive increments. The discharge rate and flow velocity required to initiate residue movement are identified. Hydraulic measurements are used to calculate the ratio of critical flow depth to residue diameter, critical Reynolds number, critical shear stress, dimensionless shear stress, and boundary Reynolds number. Regression equations are developed to relate dimensionless shear stress to boundary Reynolds number. Close agreement is found between predicted and actual dimensionless shear stress. If residue diameter is known, the regression equations can be used to estimate the beginning of motion for other residue materials. Information obtained in this study can be used to help identify proper residue management practices for conservation tillage systems.
 
One basic principle of fluid mechanics used to resolve practical problems in hydraulic engineering is the Bernoulli theorem along a streamline, deduced from the work-energy form of the Euler equation along a streamline. Some confusion exists about the applicability of the Bernoulli theorem and its generalization to open-channel hydraulics. In the present work, a detailed analysis of the Bernoulli theorem and its extension to flow in open channels are developed. The generalized depth-averaged Bernoulli theorem is proposed and it has been proved that the depth-averaged specific energy reaches a minimum in converging accelerating free surface flow over weirs and flumes. Further, in general, a channel control with minimum specific energy in curvilinear flow is not isolated from water waves, as customary state in open-channel hydraulics.
 
Thirty well-established 240L bioretention mesocosms were used to investigate retention of dissolved nutrients by bioretention systems. Ten mesocosms were comprised of 80 cm sandy loam, ten of 80 cm loamy sand, and ten of pea gravel with 20 cm of loamy sand. Half were vegetated with shrubs/grasses, while the other half had no vegetation (barren). In the first part of our study, the loam and sand mesocosms were dosed with synthetic storm water comprising 0.8 mg L−1 total phosphorus (TP) and 4.8 mg L−1 total nitrogen (TN). TP retention in the vegetated loam was 91% compared to 73% in the barren, and TN retention was 81% compared to 41% in the barren loam. TP retention was 86–88% in the sand treatments, while TN retention in the vegetated sand was 64%, compared to 30% in the barren. In the second part of our study, all 30 mesocosms were loaded weekly with 45 cm of tertiary effluent with high nutrient loads (22.3 m year−1 hydraulic load at a flow-weighted average of 4.5 mg L−1 TP and 4.8 mg L−1 TN, or 1,012 kg ha−1 year−1 TP and 1,073 kg ha−1 year−1 TN). After 50 weeks of loading, cumulative TP retention was 92% in the vegetated loam, 67% in the sand, and 44% in the vegetated gravel. However, TP retention by barren media was 56% in the loam, 39% in the sand, and 14% in the gravel. Cumulative TN retention was 76% in the vegetated loam, 51% in the sand, and 40% in the vegetated gravel. In contrast, maximum TN removal by barren media was 18% in the loam. The increase in TP retention by vegetated systems substantially exceeds phosphorus uptake rates for plants, suggesting that other processes are involved. The increase in TN retention by vegetated systems also exceeds nitrogen uptake rates for plants, suggesting that denitrification is involved. Yes Yes
 
Numerical simulations of free surface flows are important to provide a prediction tool for the optimal management of irrigation canals. Here we consider an alternative to solving the shallow water equations. We propose a free surface model in which the vertical component of the water current is fully resolved. We believe that such a detailed description can be useful to model the °ow around gates or in other situations where the vertical structure of the °ow will be important such as in the case of sediment transport and deposition. Our approach is based on a two-fluid Lattice Boltzmann model. We compare the predictions obtained from numerical simulation and experiments performed on a laboratory micro-canal facility.
 
The hydraulics of broad-crested weirs is influenced by the weir inflow design. It is highlighted herein that the inflow geometry including the rounding of the weir upstream edge has a marked effect on the flow pattern and discharge coefficient. In the case of an upstream vertical wall, the optimum design includes a rounded upstream corner (Harrison 1967, Bos 1976, Montes 1998). An upstream side slope may provide an alternative design for embankment structure although with a lower discharge coefficient (Sargison and Percy 2009).
 
The flow features over the broad‐crested weir with vertical upstream wall and sharp‐crested corner are analyzed experimentally. Only the long‐crested weir is considered, for which the discharge coefficient remains practically constant. For a relative overflow depth between 10% and 40%, the surface profile, the bottom pressure profile, the boundary separation profile, and the velocity profiles close to the upper corner are self‐similar, provided effects of scale may be dropped. For extremely long‐crested weirs, undular flow occurs. The first wave profile is shown to be identical with the solitary wave profile. The main properties of the undular hydraulic jump are explored. The broad‐crested weir is characterized by insensitivity to tailwater submergence. The modular limit is found practically constant at 75% of the tailwater level, independent of the relative head on the weir. The discharge‐head relation for submerged flow is analyzed under a novel approach. Finally, recommendations are specified under which a broad‐crested weir may be used as a discharge measurement structure.
 
Vapor-pressure deficit (VPD) affects evapotranspiration, water-use efficiency, and radiation-use efficiency of crops. VPD calculation methods were evaluated for a semiarid environment in the Southern Great Plains. Air temperature and relative humidity were measured near Bushland, Texas, during 1992 and 1993. Temperature and relative humidity were measured at 0.17 Hz (6 s), averages were recorded for each 15-min period, and daily (24-hr) maximums, minimums, and averages were recorded. VPD, actual vapor pressure, and dew-point temperatures were computed and averaged for each 15-min period and day. Methods that used mean daily dew-point temperature to compute daily actual vapor pressure performed well, and methods that used hybrid calculations based on maximum and minimum air temperature and relative humidity performed the worst. Methods using one-time-of-day dew-point temperatures as recommended by the 1990 ASCE Manual No. 70 should be used with caution in this environment. Weather data sets containing maximum and minimum temperatures and daily mean dew-point temperature should provide the most accurate calculations of VPD in this environment.
 
Four rectangular sluice gates were calibrated for submerged-flow conditions using nearly 16,000 field-measured data points on Canal B of the B-XII irrigation scheme in Lebrija, Spain. Water depth and gate opening values were measured using acoustic sensors at each of the gate structures, and the data were recorded on electronic data loggers. Several gate calibration equations were tested and it was found that the rectangular sluice gates can be used for accurate flow measurement. The Energy-Momentum (E-M) equations proved to be sound. The calibration of the contraction coefficient, to be used in the energy equation, allowed good estimations of the discharge for three of the four gates studied. The gate for which the E-M method did not perform satisfactorily was located at the head of the canal with a unique nonsymmetric approach flow condition. Alternatively, we investigated the performance of the conventional discharge equation. The variation of the discharge coefficient, Cd, with the head differential, Δh, and the vertical gate opening, w, suggests that Cd be expressed as a function of these two variables. For the sluice gates considered in this study, the best empirical fit was obtained by expressing Cd as a parabolic function of w, although an exponential expression tested previously by other writers also produced satisfactory results. The greatest uncertainty in the variables considered in this study was in the calculated coefficient of discharge, and based on the uncertainty analysis, it is possible to quantify the uncertainty in the estimated discharge through a calibrated sluice gate. The discharge uncertainty in each of the four gates in this study decreases with increasing gate opening, and it decreases slightly with increasing head differentials.
 
The paper proposes a new method to tune robust distant downstream PI controllers for an irrigation canal pool. The method emphasizes the role of gain and phase margins in the controller design, by linking the selection of these robustness indicators to the time domain specifications. This leads to link the frequency domain approach used by automatic control engineers to the time domain approach used by hydraulic engineers. The maximum error corresponding to an unpredicted perturbation is shown to be directly linked to the gain margin and the settling time to the phase margin of the controlled system. The tuning method gives analytical expressions for the controller parameters as function of physical parameters of the canal pool in order to satisfy desired performance requirements. The model is first expressed in terms of dimensionless variables, in order to get generic tuning formulas. The dimensionless PI coefficients are then expressed as functions of time-domain performance requirements. The PI tuning method is evaluated by simulation on a full nonlinear model for a canal pool taken from the ASCE Test Cases.
 
This paper examines the problem of routing known water demands through gate-controlled, open-channel irrigation delivery systems. Volume-compensation principles were used to route multiple demands in multiple-pool canal systems. The volume-compensation method schedules each demand change individually under the assumption of a series of steady states and superimposes the individual results. Volume-compensation routing schedules were computed for two of the test cases proposed by the ASCE Task Committee on Canal Automation. Alternative routing schedules were computed with the gate-stroking method, which is an inverse solution of the unsteady-flow equations. Both solutions were tested through unsteady-flow simulation. While not as effective as gate-stroking solutions, volume-compensation solutions performed satisfactorily under ideal flow control conditions. When subjected to realistic operational constraints, specifically constraints on the flow regulation interval, and also to incorrect canal hydraulic roughness information, both methods performed similarly.
 
Schematic view of a canal with two pools
Downstream water level variation
Velocity variation
Global test
Normalized estimation error e hn = (Y k − ˆ Y k )/ √ V e h
This paper deals with the problem of fault detection and isolation in irrigation canals. We develop a method which combines static and dynamic data reconciliation for the validation of measurements, detection and isolation of sensors and actuator faults and reconstruction of missing data. Static data reconciliation uses static models at a regulation gate to validate measurements and detect sensor and actuator faults. It also enabled us to detect a drift in the stage discharge rating curve. The dynamic data reconciliation uses additional measurements and a dynamic model of the canal in order to validate measurements and detect faults and withdrawals. The combination of the two methods allowed us to distinguish between withdrawals and faults. Both methods are evaluated on measurements from a real irrigation canal located in the South of France.
 
Most canals have either long travel times or insufficient in-canal storage to operate on demand. Thus most flow changes must be routed through the canal. Volume compensation has been proposed as a method for easily applying feedforward control to irrigation canals. Software for automated canal management (SacMan) includes both feedforward routing with volume compensation and distant downstream-water-level control. SacMan was implemented on the WM canal of the Maricopa-Stanfield Irrigation and Drainage District, Stanfield, Ariz. Field testing was conducted for a 30 day period during 2004 where more than 50 deliveries to users were made with feedforward control. This paper presents results from some of these field tests and demonstrates the degree of water-level control achievable with combined feedforward (routing)-feedback control.
 
Based on the companion paper results, a robust tuning method is derived to tune a PI controller that fulfills the design requirements for a single pool with different hydraulic conditions. The PI controller parameters are obtained analytically as function of the physical parameters of the canal pool. Important implementation issues are also considered. Rules are provided for the sampling time selection in order to recover the continuous-time performance. When the sampling time is imposed, it has to be included in the controller design, by modifying the delay of the system. A simple way is proposed to take account of the gate opening as control action variable, instead of the upstream discharge. This robust PI tuning method is evaluated by simulation on a full nonlinear model of two different canal pools for different flow conditions and different implementations: continuous-time control, discrete-time control, using the discharge or the gate opening as control action variable. Simulation results show that the method leads to efficient realistic PI controllers for a canal pool
 
On steep canals, distant downstream-water-level control can be challenging. The Software for Automated Canal Management was developed, in part, to test various distant downstream water-level controllers. It was implemented on the WM canal of the Maricopa Stanfield Irrigation and Drainage District, Stanfield, Ariz. to compare the performance of various controllers. In 2004, Clemmens and Schuurmans used optimization to determine the coefficients for a variety of controllers. These controllers vary in their complexity from a series of simple, single-input-single-output, proportional-integral controllers to a fully centralized, multiple-input-multiple-output, optimal controller. The controller design also varies regarding which pools are under downstream, or upstream, control and according to the conditions (e.g., flow rate) assumed for controller design. These controllers were tested under actual operating conditions and with unscheduled disturbances. The results of these tests are presented in this paper.
 
Computing accurately the response time of an open channel is of extreme importance for management operations on canal networks, such as feed-forward control problems. The methods proposed in the literature to approximate the response time do not always account for the influence of a cross structure at the downstream end of a canal pool, which may have a significant impact on the response time. This paper proposes a new approach to compute the response time, accounting explicitly for the backwater and the feedback effects due to the downstream cross structure. The method provides a distributed analytical expression of the response time as a function of the characteristics of the canal geometry, roughness and of the downstream cross structure. A test canal with a weir or a gate at the downstream end is used to compare the new method with some of the others. Results show that the proposed expression accurately reproduces the response time for various backwater and downstream boundary conditions.
 
In this paper, two internal model control (IMC) controllers using gain-scheduling techniques are proposed and compared for open-channel systems that allow to deal with large operating conditions. In particular, in one side, a linear parameter varying (LPV) model for an open-flow channel system based on a second-order delay Hayami model is proposed. This model will allow one to design a classic gain-scheduling strategy for the IMC controller. On the other side, the LPV model is discretized in a set of linear time invariant (LTI) models corresponding to different operating points. For each LTI model a LTI IMC controller is designed off-line. Then, a supervised gain-scheduler detects on-line which is the LTI model that represents better the open-flow channel system at the current operating point and decides which is the LTI controller that should be used. Finally, both approaches will be applied to a simulated open canal: the Lunax gallery located at Gascogne, France.
 
In open channel flows, the relationship between specific energy and flow depth presents a singularity at critical flow conditions. Although the concept of critical flow was first introduced as a singularity of the backwater equation (Bélanger 1828), it was associated with the idea of minimum specific energy by Bakhmeteff (1912). This approach is now commonly used (Henderson 1966, Chanson 2004) including herein. Numerous solutions of the critical flow conditions were proposed for flat channels with hydrostatic pressure distributions. Herein solutions for non-hydrostatic pressure distribution flow situations are developed, and compared with experimental measurements.
 
In open channels, the relationship between the specific energy and the flow depth exhibits a minimum, and the corresponding flow conditions are called critical flow conditions. Herein they are re-analysed on the basis of the depth-averaged Bernoulli equation. At critical flow, there is only one possible flow depth, and a new analytical expression of that characteristic depth is developed for idealfluid flow situations with non-hydrostatic pressure distribution and non-uniform velocity distribution. The results are applied to relevant critical flow conditions : e.g., at the crest of a spillway. The finding may be applied to predict more accurately the discharge on weir and spillway crests.
 
This paper is devoted to the improvement of the measuring range of inverted V-notch (IVN) weir, a practical linear sharp-crested weir, designed earlier by the writers. The range of linearity of IVN can be considerably enhanced (by more than 200%) by the addition of a retangular weir of width 0.265W (W = half crest width) at a depth of 0.735d (d = altitude of IVN), above the crest of the weir, which is equivalent to providing at this depth two vertical straight lines to the IVN, resulting in a chimney-shaped profile; hence, the modified weir is named chimney weir. The design parameters of the weir, that is, the linearity range, base flow depth, and datum constant, which fixes the reference plane of the weir, are estimated by solving the nonlinear programming problem using a numerical optimization procedure. For flows through this weir above a depth of 0.22d, the discharges are proportional to the depth of flow measured above a reference plane situated at 0.08d above the weir crest for all heads in the range 0.22d <= h <= 2.43d, within a maximum percentage deviation of ±1.5 from the theoretical discharge. A significant result of the analysis is that the same linear head-discharge relationship governing the flow through the IVN is also valid for the extended chimney weir. Experiments with three different chimney weirs show excellent agreement with the theory by giving a constant average coefficient of discharge for each weir.
 
The most common types of weirs are the broad-crested weir, the sharp-crested weir, the circular-crested weir and nowadays the ogee crest weir. Advantages of the cylindrical weir shape include the stable overflow pattern, the ease to pass floating debris, the simplicity of design compared to ogee crest design and the associated lower costs. In this study, the authors describe new experiments of circular weir overflows, with eight cylinder sizes, for several weir heights and for five types of inflow conditions : partially-developed inflow, fully-developed inflow, upstream ramp, upstream undular hydraulic jump and upstream (breaking) hydraulic jump. Within the range of the experiments, the cylinder size, the weir height D/R and the presence of an upstream ramp had no effect on the discharge coefficient, flow depth at crest and energy dissipation. But the inflow conditions had substantial effects on the discharge characteristics and flow properties at the crest. Practically the results indicate that discharge measurements with circular weirs are significantly affected by the upstream flow conditions.
 
Laboratory experiments are conducted to evaluate the hydraulic characteristics of several circular flumes. The circular flume is a simple and low‐cost water measuring device constructed from two pieces of pipes, one installed vertically inside the other. The ratio of the diameter of the inner column to the flume itself is approximately one‐third. The presence of the inner column reduces the cross section of the flow, creating a critical flow condition. A gauge is installed at the upstream side of the inner column to measure the depth of the water upstream of the critical flow section. The reading on the gauge is directly related to the flow rate. The results of the laboratory experiments showed that the circular flumes can be successfully used to measure the flow rate in open channels. Based on the results of the laboratory experiments, a computer model is developed for the calibration of circular flume. The computer model is tested using data from flumes installed in the laboratory and in the field.
 
Flow chart showing methodology
Evolution of crop patterns in Fuente Palmera irrigation district
Climate change will lead to changed demands on existing irrigation systems. This paper presents a methodology for investigating the performance of irrigation networks under climate change, and applies this to an irrigation network in Cordoba, southern Spain. The methodology uses emission scenarios (A2 and B2) developed by the Intergovernmental Panel on Climate Change. A global climate model (HadCM3) is used with downscaling to predict climate variables for 2050 and 2080 under the emission scenarios. European agricultural policy scenarios are used to predict future cropping patterns. Irrigation water requirements are then estimated for various combinations of these climate and cropping pattern scenarios, and the performance of the irrigation network is evaluated in terms of the equity and adequacy of pressure at the outlets, using EPANET. The methodology was applied to the Fuente Palmera irrigation district, which supplies water on-demand for drip irrigation. The results show that climate change would have a major impact on network performance with the existing cropping pattern, but that expected changes in cropping pattern would reduce this impact. Accepted for publication
 
Net radiation (Rn) is a key variable for computing reference evapotranspiration and is a driving force in many other physical and biological processes. The procedures outlined in the Food and Agriculture Organization Irrigation and Drainage Paper No. 56 [FAO56 (reported by Allen et al. in 1998)] for predicting daily Rn have been widely used. However, when the paucity of detailed climatological data in the United States and around the world is considered, it appears that there is a need for methods that can predict daily Rn with fewer input and computation. The objective of this study was to develop two alternative equations to reduce the input and computation intensity of the FAO56-Rn procedures to predict daily Rn and evaluate the performance of these equations in the humid regions of the southeast and two arid regions in the United States. Two equations were developed. The first equation [measured-Rs-based (Rs-M)] requires measured maximum and minimum air temperatures (Tmax and Tmin), measured solar radiation (Rs), and inverse relative distance from Earth to sun (dr). The second equation [predicted-Rs-based (Rs-P)] requires Tmax, Tmin, mean relative humidity (RHmean), and predicted Rs. The performance of both equations was evaluated in different locations including humid and arid, and coastal and inland regions (Gainesville, Fla.; Miami, Fla.; Tampa, Fla.; Tifton, Ga.; Watkinsville, Ga.; Mobile, Ala.; Logan, Utah; and Bushland, Tex.) in the United States. The daily Rn values predicted by the Rs-M equation were in close agreement with those obtained from the FAO56-Rn in all locations and for all years evaluated. In general, the standard error of daily Rn predictions (SEP) were relatively small, ranging from 0.35 to 0.73 MJ m-2 d-1 with coastal regions having lower SEP values. The coefficients of determination were high, ranging from 0.96 for Gainesville to 0.99 for Miami and Tampa. Similar results, with approximately 30% lower SEP values, were obtained when daily predictions were averaged over a three-day period. Comparisons of Rs-M equation and FAO56-Rn predictions with the measured Rn values showed that the Rs-M equations' predictions were as good or better than the FAO56-Rn in most cases. The performance of the Rs-P equation was quite good when compared with the measured Rn in Gainesville, Watkinsville, Logan, and Bushland locations and provided similar or better daily Rn predictions than the FAO56-Rn procedures. The Rs-P equation was able to explain at least 79% of the variability in Rn predictions using only Tmax, Tmin, and RH data for all locations. It was concluded that both proposed equations are simple, reliable, and practical to predict daily Rn. The significant advantage of the Rs-P equation is that it can be used to predict daily Rn with a reasonable precision when measured Rs is not available. This is a significant improvement and contribution for engineers, agronomists, climatologists, and others when working with National Weather Service climatological datasets that only record Tmax and Tmin on a regular basis.
 
Automated site-specific sprinkler irrigation system can save water and maximize productivity, but implementing automated irrigation is challenging in system integration and decision making. A controllable irrigation system was integrated into a closed-loop control with a distributed wireless in-field sensor network for automated variable-rate irrigation. An experimental field was configured into five soil zones based on soil electrical conductivity. In-field soil water sensors were installed on each zone of the distributed wireless sensor network and remotely monitored by a base station for decision making. The soil water sensors were calibrated with a neutron probe and individually identified for their response ranges at each zone. Irrigation decisions were site-specifically made based on feedback of soil water conditions from distributed in-field sensor stations. Variable-rate water application was remotely controlled by the base station to actuate solenoids to regulate the amount of time an individual group of sprinkler nozzles was irrigating in a 60-s time period. The performance of the system was evaluated with the measurement of water usage and soil water status throughout the growing season. Variable water distribution collected in catch cans highly matched to the rate assigned by computer with r2=0.96. User-friendly software provided real-time wireless irrigation control and monitoring during the irrigation operation without interruptions in wireless radio communication.
 
Top-cited authors
Richard G Allen
  • University of Idaho
Ricardo Trezza
  • University of Idaho
W.G.M. Bastiaanssen
Charles Burt
  • California Polytechnic State University, San Luis Obispo
Terry A. Howell
  • United States Department of Agriculture