Quantifying both climate and land use/cover changes on runoff variation in Han River basin, China

Climate change and land use/cover change (LUCC) can both exert great impacts on the generation processes of precipitation and runoff. However, previous studies usually neglected considering the contribution component of future LUCC in evaluating changes in hydrological cycles. In this study, an integrated framework is developed to quantify and partition the impact of climate change and LUCC on future runoff evolution. First, a daily bias correction (DBC) method and the Cellular Automaton-Markov (CA-Markov) model are used to project future climate and LUCC scenarios, and then future runoff is simulated by the calibrated Soil and Water Assessment Tool (SWAT) model with different climate and LUCC scenarios. Finally, the uncertainty of future runoff and the contribution rate of the two driving factors are systematically quantified. The Han River basin in China was selected as a case study. Results indicate that: 1) both climate change and LUCC will contribute to future runoff intensification, the variation of future runoff under combined climate and LUCC is larger than these under climate change or LUCC alone; 2) the projected uncertainty of median value of multi-models under RCP4.5 (RCP8.5) will reach 18.14% (20.34%), 12.18% (14.71%), 11.01% (13.95%), and 11.41% (14.34%) at Baihe, Ankang, Danjiangkou, and Huangzhuang stations, respectively; 3) the contribution rate of climate change to runoff at Baihe, Ankang, Danjiangkou, and Huangzhuang stations under RCP4.5 (RCP8.5) are 91%–98% (84%–94%), while LUCC to runoff under RCP4.5 (RCP8.5) only accounts for 2%–9% (6%–16%) in the annual scale. This study may provide useful adaptive strategies for policymakers on future water resources planning and management.