Journal of Irrigation and Drainage Engineering

A methodology based on solving a large-scale nonlinear programming problem is presented for the optimal design and operation of pumping stations. Optimum design and operation refers to the selection of pump type, capacity, and number of units as well as scheduling the operation of irrigation pumps that results in minimum design and operating cost for a given set of demand curves. The design criteria for such pumping stations are based fundamentally on some important and critical parameters, such as pump capacity, number of units, types of pumps, and civil works. The optimization process consists of three main steps: (1) determination of minimum yearly consumed energy; (2) minimization of the total cost for all sets of pumping stations; and (3) selection of the least-cost set among the feasible sets of pumping stations, recognizing a combination of the cited criteria. The computational analysis is based upon one major objective function and a computer program, which is developed to solve the generated equations. Application of the model to the Farabi Agricultural and Industrial Project, Iran, shows considerable savings, about 25% in total annual cost of the pumping station.

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, first with full irrigation (irrigation to fill the root zone to field capacity) and second 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 practicing 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.

In a detailed model for reservoir irrigation taking into account the soil moisture dynamics in the root zone of the crops, the data set for reservoir inflow and rainfall in the command will usually be of sufficient length to enable their variations to be described by probability distributions. However, the potential evapotranspiration of the crop itself depends on the characteristics of the crop and the reference evaporation, the quantification of both being associated with a high degree of uncertainty. The main purpose of this paper is to propose a mathematical programming model to determine the annual relative yield of crops and to determine its reliability, for a single reservoir meant for irrigation of multiple crops, incorporating variations in inflow, rainfall in the command area, and crop consumptive use. The inflow to the reservoir and rainfall in the reservoir command area are treated as random variables, whereas potential evapotranspiration is modeled as a fuzzy set. The model’s application is illustrated with reference to an existing single-reservoir system in Southern India.

The application of N fertilizers mixed with a surface irrigation stream (surface N fertigation) is widely practiced in the southwestern United States. Procedures for the optimal design and management of surface N fertigation systems are needed. The purpose of this work is to identify and define a set of performance indices that can be used to assess the relative merits of alternative design and management scenarios. Equations and solutions for quantifying the performance indices are proposed. Sample performance calculations are presented for a fertigation field experiment in which bromide ion was used as a tracer to simulate the movement of nitrate on the surface and through the soil profile.

Existing technologies have been tailored to deliver cost-effective irrigation on a railway embankment and excavated steep slopes (referred to as batters) within a semiarid environment. Irrigation is to aid the establishment of 100% grass cover within a few weeks to mitigate soil erosion problems. It is based on water sourced from a temporary excavated pond plus the use of a solar powered pump and a drip irrigation system. Railway batter erosion remediation is timed for the wet summer season when irrigation can be used to supplement natural rainfall. For a given irrigation demand and catchment area, critical (minimum) pond volume is estimated from regional charts developed for ungauged catchments. About 20% of the critical volume is added to account for evaporation losses and dead storage. Also, seepage losses need to be considered if the soil is medium to coarse textured and if the pond is not lined with an impermeable material. Initial results are very encouraging with a cost estimate of AU$2.74/m² of batter area treated (irrigated). Irrigation unit cost is expected to decrease with a larger scale irrigated batter area and the refinement of technologies and installation procedures. Although irrigation methodologies were developed for railway embankments and excavated slopes, they can also be used for erosion control on steep slopes such as road embankments or excavated slopes and earth dam side slopes.

The results of experimental work leading to the development of shorter and improved stilling basins for pipe outlets are reported. The original USBR impact type VI stilling basin incorporates a floor that is depressed below the invert elevation of the pipe outlet. In the present study, efforts are made to develop an efficient stilling basin keeping the floor at the invert elevation of the pipe outlet. Experiments were conducted for two pipe diameters with Froude numbers ranging from 1.70 to 5.50. The new models were developed by conducting systematic experiments on a large number of stilling basins with different configurations of the appurtenances such as the splitter block, impact wall, baffle blocks, and end sill in terms of their shapes, sizes, and locations. A performance number has been defined to compare the performances of various stilling basins using a constant experimental running time and same erodible material for each model. The shapes and sizes of various appurtenances and corresponding performance results are presented. The performance of the newly developed efficient and economical stilling basins are compared with the performance of the USBR impact type VI stilling basins for pipe outlets within the range of the Froude numbers tested.

Models of soil water transport often calculate conductivity K from the water retention curve (WRC). Residual water content $\left({\theta }_r\right)$ has been defined as θ where $K=0\text{.}$ When nonisothermal, coupled vapor and liquid water transport are considered, ${\theta }_r>0$ fails because vapor transport often reduces θ to near zero. The author’s objective was to test a model that used unsaturated $K\left(\theta \right)$ with θ dependence typical of ${\theta }_r>0\text{,}$ while a WRC with ${\theta }_r=0$ was used elsewhere in the model. The system was a closed column of steady state, unsaturated, nonisothermal fine quartz sand with temperature (T) ranging from 5 to 40°C. Soil parameters were adjusted to simulate replicated experimental data from one initial θ condition. The model predicted θ and T within the range of the experimental data and reproduced the sharp drying front. It also satisfactorily modeled experiments with several different initial θ. Model heat flux predictions averaged 11% more than measured values. Experiments performed with two soil column lengths were not substantially different.

In this study, a zero-inertia model (ZIMOD) is presented to simulate all phases of border and furrow irrigation systems. The governing equations were discretized using a control volume of moving cells, by procedures reported in the literature for borders and for furrows. Later, the discretized equations were linearized by applying a Taylor series expansion according to the Newton-Raphson procedure, and then the algebraic linearized equations were iteratively solved using the Gaussian elimination technique. The ZIMOD was verified against several field experimental data and output of various numerical models in the SIRMOD package. Computational times, errors in predicting advance and recession trajectories, and estimated runoff and infiltrated volumes were compared. All models used in the comparative analysis predicted the advance and recession times and the infiltrated and runoff volumes satisfactory. However, models in the SIRMOD package were computationally faster than ZIMOD.

This paper examines the potential of artificial neural networks (ANN) in estimating the actual crop evapotranspiration (ET) from limited climatic data. The study employed radial-basis function (RBF) type ANN for computing the daily values of ET for rice crop. Six RBF networks, each using varied input combinations of climatic variables, have been trained and tested. The model estimates are compared with measured lysimeter ET. The results of the study clearly demonstrate the proficiency of the ANN method in estimating the ET. The analyses suggest that the crop ET could be computed from air temperature using the ANN approach. However, the present study used a single crop data for a limited period, therefore further studies using more crops as well as weather conditions may be required to strengthen these conclusions.