What is the main driving force of hydrological cycle variations in the semiarid and semi-humid Weihe River Basin, China?

Climate change is often cited as the main driver of changes in the hydrological cycle; however, this idea has been challenged in recent years for areas where human activities are frequent and intensive. Western China has experienced significant land use/cover change (LUCC) and human activities have intensified since the 1980s, with important consequences on the hydrological cycle. In this study, we focused on the Weihe River Basin (western China) and aimed at detecting the main driving forces acting on the hydrological cycle of this area among climate changes, LUCC, and direct human activities. Six scenarios were designed to evaluate the impacts of LUCC and climate factors on the hydrological cycle through the Soil Water and Assessment Tool (SWAT) model; moreover, we quantified the contributions of changes in the meteorological factors, direct human activities, and LUCC on the streamflow. We found that streamflow and soil moisture (SM) decreased at rates of -6.52m/s/10a and -17.78mm/10a, respectively, while evapotranspiration (ET) increased at a rate of 38.83mm/10a between 1989 and 2015. Among these factors, precipitation apparently had the major impact on ET and SM, while direct human activities were the main cause of streamflow reduction; on the other hand, the influence of LUCC on the hydrological variables was less than that of climate changes and direct human activities. Interestingly, the effect of temperature on the hydrological cycle has strengthened since year 2000, suggesting that climate changes (i.e., global warming) will have an increasingly important impact on the hydrological cycle of the Weihe River Basin.