Effects of climate change and anthropogenic activities on runoff change of the Weihe River basin, Northwest China

The Weihe River has experienced a significant runoff decline in the past few decades, but the detailed and systematic analysis of different sub-regions of the Weihe River basin (WRB) for a long time is insufficient. Based on the data of five hydrological stations from 1957 to 2018, this study investigated the variation of annual runoff both in the whole Weihe River basin (WWRB) and its sub-regions: the upper, middle, and lower reaches of the Weihe River (URWR, MRWR, LRWR, respectively), the Jing River basin (JRB), and the Beiluo River basin (BLRB). Moreover, the contribution of climate change and anthropogenic activities on runoff change was quantified by double mass curve (DMC) and hydrological sensitivity analysis (HSA) methods. The results showed that runoff of the URWR, MRWR, JRB, BLRB, and WWRB showed significant downward trends, and with the change-point years of 1993, 1990, 1996, 1994, and 1993, respectively. Both results of DMC and HSA showed that anthropogenic activities were the main factors for runoff reduction. The contribution of human activities was largest in the JRB and BLRB, whereas lowest in the MRWR. Over the study period, land use has changed significantly in the basin, mainly manifested in the reduction of farmland, and the increase of construction land and grassland, indicating that intense anthropogenic activities have taken place. Moreover, the total water consumption of the WWRB increased evidently, which exacerbated the contradiction between supply and demand of water resources. The results of HSA showed that runoff was more sensitive to precipitation than to E-p. Precipitation reduced the runoff, while E-p increased runoff in the basin. The results of this study are helpful for understanding the regional hydrological situation in more detail, and can act as a reference for formulating reasonable water resources allocation schemes.