Optimization of inter-sectorial water reallocation for arid-zone megacity-dominated area

Current water demand management of megacity-dominated areas in arid-zones should be revised to optimize water allocation for sustainable development. A novel hierarchical optimization model is proposed and examined for such an area in the arid zone of Iran. The model can significantly increase water economic efficiency, reduce unsatisfied demand, and maintain necessary agricultural production. Model sub-optimization provides the cropping pattern and transient four-phenological-stage deficit-irrigation strategy that maximizes economic benefit per unit agricultural allocation. The model employs a nonlinear benefit function for industry, a linear benefit function for service, and a cubic benefit function for deficit-irrigated agriculture. If available water is unchanged, optimal economic benefit increases 283 percent from the current situation. This requires decreasing agricultural water allocation, changing cropping patterns, using deficit irrigation, and increasing development of industrial and service sectors. If annual available water decreases by 25%, or by 40%, net economic benefit can increase 101% and 19%, respectively.