Evaluating the impacts of anthropogenic, climate, and land use changes on streamflow

Several factors, including natural and human-induced, can affect river discharge. This study aims to examine the influence of land use changes and climate change on the monthly average rainfall time series in the Talar River Basin, situated in northern Iran. To investigate the impact of human factors, namely land use change and point source operations, on monthly average streamflow, the DBEST method was used to detect any breakpoint in the streamflow time series caused by gradual changes in land use and climate. The SWAT model was used to simulate the basin at two stations, Kiakola and Shirghah, between 2001 and 2020. The land use maps were created for the years 2001 and 2019. Calibration and validation at the Kiakola station showed that the Nash-Sutcliffe model (NSE) had an efficiency of 0.8 and 0.76, respectively, while at the Shirghah station, the same values were 0.84 and 0.75. Findings revealed that human activities, specifically the combined impact of land use change and point source operations, had a 60% influence on the monthly average streamflow of the Talar River. Further showed that the combination of land use and harvesting played the most significant role in the basin's outflow on a monthly scale.