Spatial and temporal variation of water yield in the highly managed basin Zayandeh Rud

This study investigates the applicability of a Soil and Water Assessment Tool (SWAT) model in predictions of the water yield of the Zayandeh Rud river basin. Meteorological and hydrological data were collected for a period of (۱۹۹۲-۲۰۱۸). In addition, Digital Elevation Model, land use, and soil maps were also extracted from suitable databases. Geographic information system (GIS) software was applied in combination with SWAT to process the spatial data and simulate the streamflow record. The model was calibrated (۱۹۹۵-۲۰۰۹) and validated monthly for the next period (۲۰۰۹-۲۰۱۸). A good correlation between the simulated and observed data during the calibration and validation was found using statistical measures such as the Nash-Sutcliffe Efficiency (NSE>۰.۶۵%) the standard deviation ratio (RSR<۰.۶). The model is suitable for estimating the water yield. Results showed eastern and northern regions of the basin contributed to the smallest percentage of the water yield. In contrast, the western region contributed to trh largest percentage of the water yield in the area.