Evaluation of Environmental and Agricultural Sustainability Indices of Zarrinehrud and Siminehrud River Basins

In the arid and semi-arid regions, agriculture has led to decline in water levels in major lakes such as the Aral Sea, Urmia, Hamoun and Bakhtegan lakes. The major objective of the present study was to evaluate the environmental and agricultural sustainability of Zarrinehrud and Siminehrud river basins as the largest sub-basin of Urmia Lake basin. The sustainability index was calculated using reliability, resilience, and vulnerability performance criteria. In this study, the irrigation water deficit (IWD) index was calculated for the irrigation districts. Irrigation demand and irrigation water deficit indices were calculated using WEAP21 model. Results showed that the environmental sustainability of Zarrinehrud and Siminehrud river basins to supply the environmental flow requirements of the Urmia Lake during the studied period was 0.39 and 0.41 respectively. Nevertheless, the agricultural sustainability index of Zarrinehrud and Siminehrud river basins was 0.64 and 0.74 respectively. Moreover, the amount of IWD index showed that water demand for all irrigation districts has not been fully met. The above results indicated that the Zarrinehrud and Siminehrud river basins were unstable both in terms of the environment and agriculture. Whereas during the study, the changes in land under cultivation in most irrigation districts had an increasing trend, ttherefore, it can be concluded that agricultural development and the addition of water harvests for agricultural use have been the main cause of environmental and agricultural instability.