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In the present study, an integrated soil water balance algorithm was coupled to a non-linear optimization model in order to carry out water allocation planning in complex deficit agricultural water resources systems based on an economic efficiency criterion. The LINGO 10.0, optimization package has been used to evolve at optimal allocation plan of surface and ground water for irrigation of multiple crops. The proposed model was applied for Qazvin Irrigation Command Area, a semi-arid region in Iran. Various scenarios of conjunctive use of surface and ground water along-with current and proposed cropping pattern have been explored. Some deficit irrigation practices were also investigated. The results indicate that conjunctive use practices are feasible and can be easily implemented in the study area, which would enhance the overall benefits from cropping activities. The study provides various possible operational scenarios of the branch canals of the command area in the common and dry condition, which can help managers in decision making for the optimum allocation plans of water resources within the different irrigation districts. The findings demonstrate that for deficit irrigation options, the mining allowance of ground water value of the command area is greatly reduced and ground water withdrawal may be also restricted to the recharge to maintain the river-aquifer equilibrium.

The aim of this paper is develop a nonlinear optimisation model for the determination of the optimised water allocation and cropping pattern under adequate and limited water supplies. The water productivity index defined as the net profit to the volume of water used was considered as the objective function. The proposed model was executed for the Ghazvin Irrigation Network located in a semi-arid region in Iran. The results showed that among the crop types grown in the region, onion and alfalfa have the highest and lowest water productivity value, respectively. These values under drought conditions for the optimal cropping pattern of the two crops were estimated at 75 068.86 and 3054.18 Rls m À3 . The findings indicated that the overall water productivity of the irrigation network with relevant cropping pattern management might be raised to as high as 12 700 Rls m À3 under drought conditions. In normal and wet years, depending on the water available and the optimal cropping pattern, the values for this index were estimated to be 15 600 and 12 900 Rls m À3 , respectively. For the existing cropping pattern, overall irrigation network productivity is estimated at 10 600 Rls m À3 . Hence, the results demonstrated that the water productivity of an irrigation network could be improved as result of the optimal cropping pattern and deficit irrigation. For the study area, the maximum variations of this index may be fixed around 18% for different water regimes. The evaluations emphasise the important role of optimisation models in improving irrigation network efficiency and managing water in a sustainable manner. Copyright # 2008 John Wiley & Sons, Ltd.

The current challenge facing irrigation networks is to find ways to improve their operational performance. Control system design and implementation is considered as one of the most assured ways to achieve this aim. In this paper, a downstream water-level controller is presented for the first nine pools of the Narmada main canal in India. The control system consists of a remote downstream proportional-integral (PI) feedback controller with feedforward control. In this controller, each water-level regulator is adjusted based on water levels of all the pools of the canal. A linear model of the canal pool response, the integrator-delay model, is applied to define the state transitions. To evaluate the control system potential, performance criteria were considered. The results show that the designed controller has considerable potential to closely match the discharges at the downstream outlets/offtakes with those ordered by water users while maintaining the water levels throughout the length of the canal. This result is achieved providing that the estimated delay times used in the feedforward controller are varied depending on the flow rate.

Water management decisions in irrigation networks are often characterized by complexity, irreversibility and uncertainty. In the present study, an analytical hierarchy model is developed for assessing the Global Water Productivity (GWP) status of irrigation networks. For this purpose 14 criteria, affecting water productivity, and 14 major modern irrigation networks of Iran are analyzed. Dez and Saveh irrigation networks, with the relative weights of 0.112 and 0.045, show the highest and lowest GWP, respectively. The results obtained by the proposed model are evaluated using actual GWP of the irrigation networks from 5-year average field investigations. The results obtained by AHP model are in good agreement with the results determined from the field survey. However, in the proposed model, various mutual exclusive multivariate criteria are considered, offering high qualified final solution and enhancing the consistency of the decision-making process. As the proposed model can identify the effects of different parameters on the GWP of irrigation networks, it is applied as a comprehensive and practical decision-making tool with the aim of improving the performance of such systems.

As water scarcity becomes of greater concern in arid and semi-arid regions due to altered weather patterns, greater and more accurate knowledge regarding evapotranspiration of crops produced in these areas is of increased significance to better manage limited water resources. This study aimed at determining the actual evapotranspiration (ETa) and crop coefficients (Ka) in California date palms. The residual of energy balance method using a combination of surface renewal and eddy covariance techniques was applied to measure ETa in six commercial mature date palm orchards (8–22 years old) over one year. The experimental orchards represent various soil types and conditions, irrigation management practices, canopy characteristics, and the most common date cultivars in the region. The results demonstrated considerable variability in date palm consumptive water use, both spatially and temporally. The cumulative ETa (CETa) across the six sites ranged from 1299 to 1501 mm with a mean daily ETa of 7.2 mm day−1 in June–July and 1.0 mm day−1 in December at the site with the highest crop water consumption. The mean monthly Ka values varied between 0.63 (December) and 0.90 (June) in the non-salt-affected, sandy loam soil date palms with an average density of 120 plants ha−1 and an average canopy cover and tree height of more than 80% and 11.0 m, respectively. However, the values ranged from 0.62 to 0.75 in a silty clay loam saline-sodic date palm orchard with 55% canopy cover, density of 148 plants ha−1, and 7.3 m tree height. Inverse relationships were derived between the CETa and soil salinity (ECe) in the crop root zone; and between the mean annual Ka and ECe. This information addresses the immediate needs of date growers for irrigation management in the region and enables them to more efficiently utilize water and to achieve full economic gains in a sustainable manner, especially as water resources become less available or more expensive.

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