Hydrological simulation and evaluation of drought conditions in the ungauged watershed Parishan lake Iran, using the SWAT model

Lake Parishan has faced challenges of water scarcity in recent years to the extent that its water level has drastically decreased, and disappeared now. The SWAT model was utilized to evaluate changes in vegetation cover, precipitation, temperature, and evaporation on runoff and lake surface. We employed two strategies to examine runoff and lake level changes: investigating runoff variations based on land use land cover (LULC) changes and analyzing the intensity of hydrological changes during the simulation period on the watershed's runoff. One of the main challenges of the area was the lack of runoff data, in this research, for the purpose of improving simulation processes and calibration, data from donor watershed stations and Copernicus satellite information were utilized to assist other studies in investigating basins lacking runoff statistics. The results indicate runoff has been influenced by environmental changes, resulting in intensified evaporation and temperature fluctuations compared with the simulation time series. The accuracy of simulation evaluation based on runoff statistics from the neighboring Chamchit station has been more suitable. However, in the absence of sufficient statistics and information, Copernicus satellite data can be used. HIGHLIGHTS The SWAT model shows sufficient runoff simulation in an ungauged watershed. RDI and SDI could have sufficient monitoring droughtness of disappear lake Parishan. Copernicus satellite data for simulation of catchment characteristics with limited data has acceptable results. Long-term LULC changes and influences on runoff watershed were investigated.