Development of SWAT-LU model for simulation of Lake Urmia water level decreaseand assessment of the proposed actions for its restoration; Part 1: Development, calibration and validation of SWAT-LU model

The rapid drop of Urmia Lake water level in the past two decades has led to serious concerns about the future of this lake and the environmental, economic and social negative effects of its elimination. Mitigation of the current problem and restoration of the lake requires a comprehensive approach, which cannot be achieved without detail understanding about the causes of the current situation and the proper assessment of the effectiveness of the proposed measures. In the present study, a custom edition of the SWAT hydrological model, modified according to the conditions and processes of the Urmia Lake watershed (SWAT-LU version), has been developed to evaluate the above-mentioned issues. This paper (as the first of three papers to provide the results of the research), the approaches used in the development, calibration and validation of the model are presented. The results showed that the SWAT-LU model has appropriate capabilities to simulate the hydrological cycle in Urmia Lake watershed and the modifications that have been carried out can well explain the nature of these processes. The calibration indices of the model for about 80% of the hydrometric stations was within acceptable limits and the results of the simulation of Lake Urmia water volume was also very satisfactory. Furthermore, controlling the model outputs for other hydrological components showed the model's accuracy in their simulation. In summary, the results of these analyzes showed that the developed model simulates the components of the hydrological cycle of the Lake Urmia Lake with acceptable accuracy and is a suitable tool for analyzing and evaluating the effect of different measures on the amount of various hydrological components and their interaction.