Hydro-Economic Modeling of Rainfall Reduction Effect on Cropping Pattern and Farmers' Profits in the Tashk-Bakhtegan Basin

Water scarcity is one of the most important and influential factors in the pattern of crop cultivation and farmers' profits. This research was conducted to evaluate the effects of rainfall reduction on cultivation pattern and farmers' profits in the Tashk-Bakhtegan basin. To this purpose, a composed model which includes two parts, hydrological and economic was used. In the hydrological section, the water evaluation and planning system model (WEAP) and in the economic section, the positive mathematical planning model (PMP) were used. In this research, the effects of rainfall reduction at two scenarios of 20 and 40% reduction on the agricultural sector are determined by determining the amount of water delivered to this sector and then the reaction of farmers is examined through their cultivation pattern and profits. This modeling was done regionally in 5 separate zones of the Tashk-Bakhtegan basin and compared to the base year (2006-2007). The results of this research showed that with the implementation of the scenario of 20% rainfall reduction, the area under cultivation and farmers 'profits decreased by 33 and 29%, respectively, and at the scenario of 40% rainfall reduction, the amount of the cultivation area and farmers' profits decreased by 36 and 32%, respectively. Among the different crops, the most changes in the area under cultivation were related to alfalfa and the area under cultivation of rice did not changed due to its high profits.