Development of SWAT-LU Model for Simulation of Urmia Lake Water Level Decrease and Assessment of the Proposed Actions for its Restoration; (Role of Anthropogenic and Climatic Factors on Hydrological Change of the Basin and Lake)

Recognition of the reasons for the rapid drying of Urmia Lake in the last decade and the quantitative effect of various factors on this process are the first steps in developing appropriate measures to improve its conditions, which have been less well-documented. Therefore, the present study aimed to evaluate the quantitative effect of factors affecting the change of the lake water balance in two broad categories, including climate variability and human interference. For this purpose, the single and simultaneous elimination of changes in these components was analyzed using SWAT-LU model and the effect of every factor was determined by comparing the results with the actual condition. In summary, the results of these analyzes showed that during the 22-year period ending in 2009, the cumulative effect of climatic and human-induced changes in reducing the inflow into Urmia Lake was almost equal, but due to the intensification of climate variability in the second half of this period, the effect of climatic factors was dominant in the rapid negative trend of lake water level. Also, hydrologic sensitivity analysis of Urmia Lake watershed showed that a partial reduction in the amount of long-term rainfall would lead to a much higher decline in basin drainage, which would be far more effective than temperature changes. Therefore, the occurrence of weak climatic trends can lead to significant hydrological trends, which can explain the reasons for the hydrological droughts of recent decades in large parts of the country.