Separating the impacts of climate variability and human activities on the discharge and component of streamflow in Taoer River Basin, China

Abstract Climate variability and human activity are the two driving forces that alter the hydrological cycle and spatiotemporal distribution of water resources. Quantitative separation of the two drivers is crucial for regional water resource management. Relevant studies focus mainly on the quantitative attribution of streamflow changes but overlook the impact of changing environments on hydrological processes and the hydrological regime (or streamflow component). Using the Taoer River Basin (TRB) as an example, this study analyzed the impacts of climate variability and human activities on streamflow discharge in various periods and the resulting hydrological alterations. First, through the Mann–Kendall test and cumulative anomaly method, combined with the construction of the reservoir, historical streamflow data were divided into four periods (baseline period and altered periods 1, 2, and 3). Based on the proposed basic identification framework, four assessment methods (the hydrological sensitivity method, distributed hydrological model, linear regression model, and runoff restoring computation) were used, and relatively consistent estimates of streamflow attribution were obtained. Climate variability was the driving factor for streamflow changes, and the relative contributions in altered periods 1, 2, and 3 were 81% (50.34 mm), 68% (13.37 mm), and 53% (-19.23 mm), respectively, and always accompanied by changes in hydrological regimes. Climate variability and reservoir construction have different impacts on the hydrological regime at different periods, and reservoir regulation’s effect on the hydrological regime depends on climatic conditions. We further discuss the necessity of breakpoint selection and period division in the attribution of streamflow changes, and analyze the applicability of different methods with current ideas for improvement. This study not only has practical significance for water resource planning and adaptive policy formulation in the TRB but also provides a reference for similar studies.