عنوان مقاله [English]
Quantifying the impact of climate change and human activities on hydrological processes is of great importance for regional water-resource management. In this study, trend analysis and analysis of the short-term variations in annual streamflow in the Sajasrood Watershed (SW) during the period 1987–2012 were conducted using linear regression and the Pettitt test. The time series for streamflow in SW exhibits declining trends. The results show that its break point is 1998, so that the streamflow can be divided into the baseline period and the evaluation period. The Soil and Water Assessment Tool (SWAT) was employed to simulate the hydrological processes. SWAT was first calibrated at monthly time step. The NSE, PBIAS, and RSR for the calibration period (1988-1992) were 0.7, 7.3, and 0.55, respectively. The NSE, PBIAS, and RSR for the validation period (1993-1995) were 0.65, -9.4, and 0.58, respectively. The results suggest that SWAT performance was good during calibration and validation periods. The results show that the contribution rates of climate change and human activities to runoff are 33% and 67% during 1999-2012. The proposed framework can help policy makers to regulate the policies accordingly so that the river may restore to a better level and ecosystem may get improved.