Quantifying the contribution of climate changes and human activities on runoff changes in the Changhua River Basin of Hainan Island

The Changhua River Basin (CRB) of Hainan Island, China. This study quantified the impacts of climate changes and human activities on runoff changes using a novel attribution framework in the CRB. The Variable Infiltration Capacity (VIC) distributed hydrological model was used for numerical experiments to establish a novel framework. The novel framework was employed to assess the impacts of precipitation, temperature, and human activities on runoff at both basin and sub-basin scales. Additionally, the runoff change ratio (RCR, unit: dimensionless) was used to quantify the spatial variability of runoff sensitivity to precipitation and temperature. Upon analyzing the numerical experiment results, we discovered that the downstream precipitation contributed significantly, accounting for 79.62 % of runoff changes in the CRB. In contrast, human activities exerted a negative impact on runoff changes (with a contribution rate of −9.07 %). Compared with the upstream region, downstream human activities had caused more drastic changes in runoff. The average RCR in the upstream region (48.56, unit: dimensionless) was approximately 5 times greater than that in the downstream region (10.24). These findings emphasized that the upstream region served as a stabilizing region in the water cycle of the CRB. This study provided a framework for quantifying and separating the impacts of climate changes and human activities on runoff, offering insights for managing water resources. • A framework assessed climate changes and human activities on the CRB runoff changes. • Downstream precipitation rise mainly drove runoff increase in the CRB. • Human activities in the downstream region primarily reduced the CRB runoff.