Exploring the factors affecting streamflow conditions in the Han River basin from a regional perspective

Considerable attention has recently been focused on the impacts of climate change and human activities on river streamflow conditions. This study explored these effects using three hydrological modeling techniques such as multi-regression, a two-parameter hydrological model, and hydrological sensitivity analysis, followed by trend analysis and change point detection. The non-parametric Mann-Kendall test was used to analyze the trends in hydro-meteorological parameters. The non-parametric Pettitt test and double cumulative curve techniques were used to identify change points in annual streamflow series during 1978–2014. After determining the change point year to be 1997, the series were split into two parts: a pre-change (natural) period (1978–1997) and a post-change (human-induced) period (1998–2014). The hydrological models were calibrated and estimated for the pre-change (natural) period, which provided the relative change in annual streamflow for the post-change (human-induced) period. The contribution of climate variability ranged from 36.3% to 55.9%, and human activities accounted for 44.5% to 63.7% of streamflow variability. These results suggest that human activities are more impactful than climate variability. The outcomes of this study show that streamflow in the basin was influenced by climate variability, but human actions were also major driving forces in altering the streamflow.