Contributions of climate change and anthropogenic activities to runoff change in the Hongshui River, Southwest China

Changes in water resources are mainly affected by the combined effects of anthropogenic activities and climate change. The relative effects of anthropogenic activities and climate on a river basin are investigated to not only understand the hydrological response mechanism in a catchment but also manage local water resources and protect against floods and droughts. In this study, a variable infiltration capacity (VIC) model combined with a hydrologic sensitivity analysis was used to quantify the effects of anthropogenic activities and climate change on runoff in the upper reaches of the Hongshui River basin (UHRB). During 1970-2015, the runoff contribution for climate change and anthropogenic activities were 89.2% and 10.8%, respectively. This result suggests that climate is the major driver of runoff variation in the basin. However, during 1990-1999, anthropogenic activities played a decisive role in the reduction in streamflow, and the contribution percentage was 96.35%. Moreover, the impact of anthropogenic activities on runoff changed from positive to negative from the 1980s to the 2000s, and the negative effect showed a continuously increasing trend. Hydrologic sensitivity methods and hydrological modelling produced similar estimates. Our findings emphasize that the impacts of anthropogenic activities such as land use change and the operations of water conservancy projects should be properly managed.