Optimal allocation of water resources using non-dominated sorting genetic algorithm (case study: Hamidiya irrigation network)

Considering the growing limitation of water resources, a plan is needed to be made in order to optimally use water resources, especially in the agricultural sector which uses most of the water resources. A study was conducted which its objective is to optimally allocate water resources to the Hamidiyeh irrigation network cropping pattern in order to make a plan to manage the water resources consumption trend in the Hamidiyeh irrigation network. The water year 2015-2016 was divided into 36 periods which consist of 10 days and multi-objective model was created to allocate water resources to each one of 10 day periods in order to maximize the relative water use efficiency and the revenue-cost ratio using a non-dominated sorting genetic algorithm. Furthermore, another optimization model was created to minimize the error in the yield reduction estimation under deficit irrigation application situation using genetic algorithm. The obtained results of stage wise crop response factors modification model indicated that the estimated values of yield reduction under deficit irrigation application situation using the stage wise crop response factors which were proposed by former studies vary between 16.5 and 195.5 percent. The yield reduction amount of more than 100% shows an estimation error, while the yield reduction estimated using the modified stage wise crop response factors vary between 8 to 59.5 percent. The optimal water resources allocation model is a multi-objective model which has more than one optimal solution that none of them is better that the other, and the suitable solution is chosen based on managerial decision taking. As a result, three solutions were chosen as scenarios to be compared with the current water allocation situation. Results indicated that revenue-cost ratio is slightly changed under optimal water resources allocation, but relative water use efficiency is increased at least by 9%, and water use is reduced at least by 26%. Furthermore, cultivation area is increased by 192,189, and 182 hectares in the first, second, and third scenario, respectively. Net benefit was increased by 19.5 and 10.7 billion Rials in the first and the third scenario, however, it was reduced by 8.4 billion Rials in the second scenario. The amount of water consumption is considerably reduced and the relative water use efficiency and the cultivated area is increased under optimal water resources allocation which causes reuse of fallow area. Furthermore, net benefit could also be increased depending on the chosen solution.