A System Dynamics Approach for Evaluating the Impacts of Water Demand Management Policies in Kheirabad River Basin

Kheirabad river basin is part of Zohre-Jarahi basin which is rich in surface water resources. But unprincipled usage of water and soil resources and also increasing water harvesting under climate change reduced the ability of the basin to respond to water demand. Reducing water storage of the Kowsar Dam as a result of reducing surface water inflows, make a concern to meet the future water demand at the basin. Therefore, the management of water resources in this basin is essential. In this study, we used a systemic approach to identify the factor affecting water supply and demand along with feedback and interaction between different elements for studying the behavior of the water resources system over time. The results of the study showed that the available surface water decrease and groundwater balance will be negative. Also, population growth and development of the agricultural sector will lead to an increasing trend in water demand and an increase in the surface and groundwater resources withdraw. Under these circumstances, water scarcity index is increasing and the water system sustainability index is smaller than the unit. The results also revealed that under business as usual (B.a.U) condition, the vulnerability index and maximum deficit of the water system are 0.119 and 0.213, and the reliability and sustainability indices are 0.50 and 0.703, respectively. Therefore, according to the results, the probability of not meeting the increasing demand of water, thus increasing the population and the level of crop cultivation, is predicted by using available water resources during the study period. Therefore, it is necessary to apply demand-side and supply-side management policies in Kheirabad River Basin. Among water demand-side management policies, increasing irrigation efficiency and changing crop pattern, by increasing the sustainability index from 0.703 to 1, are the most efficient policies. Besides, decreasing per capita water consumption plays an important role in increasing the water sustainability index in the basin.