Evaluation of Climate Change Impacts on Agricultural Water Allocation in Qara Su Watershed, Using WEAP

Every kind of climate change on the terrestrial earth is the beginning of a chain of reactions whose effect can be directly observed on hydrological processes. Qara Su basin catchment, located in Kermanshah Province, is one of the important sub – basins of Karkheh River that, in terms of agriculture and food security, is considered as an important area in the west of Iran. In this regard, achieving reliable methods of predicting the river flows in order to plan proper operation of water resources has become increasingly significant. In this study, first, Statistical Downscaling Model (SDSM) was used to measure the large -scale data of the atmospheric general circulation model (HadCM3) in the local climate scenario, A2, which considers both the rapid economic development for the future world, the remarkable technological advances, and excessive use of the fossil fuels in future. These are measured for the meteorological parameters of temperature and precipitation in the basin of Qara Su. Then, considering the data of rainfall, temperature and flow rate during the baseline (1971-2000) and the outputs of the fine- scale model in the period (2011-2040) as well as using an artificial neural network in MATLAB 2012 the river’s discharge during the future period was simulated. Ultimately, the allocation condition of water resources and the required water for agricultural sector were simulated using the water evaluation and assessment programming model, WEAP. The results of the climate model indicated a rise in temperature and a decrease in rainfall within the desired course rather than the base period (1997-2000), so that it was followed by a 1.6 º C rise in temperature and a 1.77% decrease in rainfall all over the area. Consequently, after this increase in temperature and decrease in rainfall, a 32.62% decrease of discharge rate is estimated for Qra Su River. The result analysis of WEAP model, under the climate scenarios and given the existing under- cultivation level, indicates an increased unmet need for agriculture in the studied region for future period.