Journal of Irrigation and Drainage Engineering

This paper presents the need, value, and concept of flexible irrigation water supply systems that can deliver water with flexibility in frequency, rate, and duration under the control of the farmer at the point of application using a limited rate arranged-demand or other schedule. It introduces the needed terminology including “congestion”—how much reserve time and capacity is required to assure water delivery at the frequency and rate desired. An illustrative design procedure for the necessary pipeline and reservoir capacities is illustrated. The techniques discussed emphasize the conversion of the economical steady supply canal flows to flexible on-farm usage through the use of service area reservoirs located between the secondary and tertiary systems, and of semiclosed pipelines and/or level-top canals as automated distribution systems which facilitates the farmers’ need for daytime only variable on-farm deliveries to permit optimization of on-farm water management. This improved management is the ultimate source of increased food production after improved crop, land, and water resources have reached their maximum. The coordinated use of return flow systems is described.

Efficient on-farm use of water and labor for all methods requires a water supply flexible in frequency, rate, and duration and under the control of the irrigator at the point of application. For surface irrigation, the use of large capacity systems for supply and distribution are essential and economical, especially when considering the reduced labor needs, increased irrigation efficiency, and reduced potential high water table problems resulting from having a large, flexible supply associated with a flexible arranged-demand schedule. Automation and stability of flow at the farm turnout, comparable to a domestic system with variable flow delivery conditions, are typically accomplished by use of large capacity semiclosed pipeline systems. A cost comparison of capital investment for various sized, flexible supply systems with resulting farm water and labor costs is presented which shows the great value from the upgraded management made possible.

In this study, an evaluation has been made of the realization level of the planned targets in irrigation planning for all of the 13 water user associations (WUAs) of the Gediz Basin. This evaluation was made according to six performance indicators: level of realization of irrigation ratios, level of realization of crop pattern, dependability, adequacy, efficiency, and equity for the years 1999–2002. Seven associations were successful in irrigation ratio realization, and four were successful in crop pattern. Failure of other WUAs can be reduced by collecting farmers’ declarations and evaluating them with greater care and sensitivity. Water delivery in the general irrigation plan was found to be poor with regard to dependability and equity, and good with regard to the indicators of adequacy (except in the year 2001) and efficiency. In order to improve dependability, the period when water is diverted from the source and the period when water is needed must coincide completely. In order to improve equity, delivery of water to WUAs must be carried out taking account of water requirements predicted in the general irrigation plan. When these two indicators are improved, adequacy and efficiency will improve also.

This 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 generates small amplitude oscillations of the canal pool. The ATV procedure can be used to get the integrator delay model parameters of a canal pool, which in turn can be used to tune a PI controller using classic rules, or other rules such as the ones proposed by Litrico and Fromion. This method does not require advanced automatic control knowledge and is implemented in the SIC software developed by Cemagref, which also incorporates a supervisory control and data acquisition 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 Food and Agriculture Organization of the United Nations (FAO) has proposed using the Penman-Monteith equation as the standard for estimating reference evapotranspiration $\left({\mathrm{ET}}_0\right)$ , and for evaluating other equations. The basic obstacle to using the FAO-56 Penman-Monteith equation (FAO-56 PM) widely is the required weather data which are not available in most of the stations. In such circumstances, a simple empirical Hargreaves equation (HARG) is often used. However, this equation generally overestimates ${\mathrm{ET}}_0$ at humid locations. Therefore, HARG requires local calibration. The main objective of this study is to investigate the possibility for calibrating the equation in the Western Balkans region, South East Europe through the adjustment of Hargreaves exponent (HE). Data from Palic, Sarajevo, and Nis have been used for estimating the adjusted HE. A value of 0.424 is proposed instead of the original 0.5 as one which should be used in the adjusted Hargreaves equation (AHARG) for the Western Balkan locations. The ${\mathrm{ET}}_0$ values estimated by AHARG were compared with FAO-56 PM estimates for eight humid locations (Varazdin, Zagreb, Bihac, Novi Sad, Negotin, Kragujevac, Nis, and Vranje). Estimates by AHARG were in close agreement with FAO-56 PM estimates at most of the locations. The SEE ranged from $0.17\mathrm{mm}{\mathrm{day}}^{-1}$ for Varazdin to $0.24\mathrm{mm}{\mathrm{day}}^{-1}$ for Vranje, averaging $0.21\mathrm{mm}{\mathrm{day}}^{-1}$ . The average overestimation was about 1%. These results strongly support the use of the adjusted Hargreaves equation at humid Western Balkan locations in the case when only the temperature data are available. Further research should be undertaken for evaluating the validity of the approach presented in this paper in other regions.

Crop evapotranspiration $\left({\mathrm{ET}}_c\right)$ was measured over a clean-cultivated, mature navel orange orchard with microsprinkler irrigation located near Lindsay, California. Hourly mean latent heat flux density was determined as the residual of the energy balance equation with measured net radiation, soil heat flux density and sensible heat flux density estimated using the surface renewal method. The ${\mathrm{ET}}_c$ was compared with ${\mathrm{ET}}_o$ calculated using hourly weather data and the ASCE-EWRI Penman-Monteith equation. Following pruning and topping of the trees in the spring of 2001, the $K_{\mathrm{co}}$ values slowly increased as the canopy developed in the following season. An average $K_{\mathrm{co}}=0.82$ was observed. In the following year, the mean summertime value increased to about $K_{\mathrm{co}}=0.95$ , and in 2003 and 2004, the summertime value averaged near $K_{\mathrm{co}}=1.00$ , which is somewhat higher than observed for drip irrigated trees in southwestern Arizona and considerably higher than reported in the widely used Food and Agricultural Organization of the United Nations publications that were based on infrequent surface irrigation.

Trapezoidal open channels are designed for specified slope, specific lining materials, and for a specified design flow. These input design parameters are prone to uncertainties. The freeboard is used to confine the flow within the limits of the channel cross section and to accommodate the uncertainty effects. Because of the size of uncertainty, the flow can overtop the freeboard with a “flooding probability.” To design an optimum channel cross section for safety against overtopping, the flooding probability constrained optimum channel design concept is introduced. An optimization model was developed which has two objective functions of minimizing the total cost of the channel and minimizing the flooding probabilities subject to uniform flow equation as constraint. The constraint method of multiobjective optimization is used in which the objective of minimizing the flooding probability is converted to a constraint, and the resulting single objective optimization problem is solved. The flooding probability constraint is developed by using the first order analysis. The final single objective optimization model is highly nonlinear and requires the use of the projected augmented Lagrangian technique. The optimization model is applied for two cases, namely, channels having composite roughness and channels having uniform roughness. The solution results of the analysis established the potential of the model.

A methodology has been developed in this study wherein a genetic algorithm (GA) is used to find a global optimal solution to a groundwater flow and contaminant problem by incorporating an artificial neural network (ANN) to evaluate the objective function within the genetic algorithm. The study shows that an ANN-GA technique can be used to find the uncertainties in output parameters due to imprecision in input parameters. The ANN-GA methodology is applied to five case studies involving radial flow in a well, one-dimensional solute transport in steady uniform flow, a two-dimensional heterogeneous steady flow, a two-dimensional solute transport, and a two-dimensional unsteady groundwater flow to demonstrate the efficiency and effectiveness of the developed algorithm. The results show that, with this approach, one can successfully measure the uncertainty in groundwater flow and contaminant transport simulations and achieve a considerable reduction in computational effort when compared to the vertex method that has been widely used in the past.

First, this paper presents a new flume for measuring flow discharge in sloping channels, originally proposed by Samani and Magallanez for use in a horizontal channel. The flume is obtained by inserting two semicylinders in a rectangular cross section. Then, using dimensional analysis and the self-similarity theory, the stage-discharge relationship of the flume is theoretically deduced. For determining the two coefficients of the power stage-discharge equation, some experimental runs are carried out using flumes characterized by different values of the contraction ratio (ranging from 0.17 to 0.81) and of the flume slope (ranging from 0.5 to 3.5%). Finally, for a given range of the contraction ratio, the relationships for estimating the two coefficients of the stage-discharge equation are obtained.

A head loss concept, new to the stream-aquifer interaction, is introduced for modeling laboratory observations. Using this concept, the equation applicable to fully penetrating streams is modified to account for the head loss at the entrance. The modified model is able to explain and fit the observed laboratory data correctly. Equations are proposed to calculate the hydraulic diffusivity of aquifer and head loss at the entrance from the estimate of diffusivity obtained without considering the head loss. An optimization approach is also proposed to estimate the hydraulic diffusivity of the aquifer and head loss from the observed groundwater heads at different sections.