Evaluating the Combined Impacts of Anthropogenic Disturbances and Climate Change on Future Streamflow Variations in the Minjiang River Basin

Abstract

Future streamflow projections are critical for water management. In this study, we coupled the Geomorphology-Based Ecohydrological Model (GBEHM) with the Physics-aware Hybrid Learning and eXtreme Gradient Boosting models to provide a preliminary assessment of streamflow variations in the Minjiang River basin (MRB) over the period of 2020–2099 under the emission scenarios of five CMIP6 models, using data from the 2010s as the baseline. We considered both climatic and anthropogenic influences, assuming that the current anthropogenic disturbances and river network configuration will remain unchanged. The performance of the GBEHM is acceptable, with error metrics exceeding 0.80 and 0.60 before and after the impoundment of the Zipingpu Reservoir, respectively. The cascade of data-driven models demonstrates good performance, with error metrics exceeding 0.90 over the whole simulation period. Under the influence of climate change, the decadal mean streamflow at Zipingpu station will decrease by 2.73–12.16% before 2069 and increase thereafter, while at Gaochang station, it will generally increase by 1.44–13.67% after 2020. Moreover, the decadal mean streamflow at Pengshan station will increase by 13.22–36.41% over the coming decades. However, the combined effects of anthropogenic disturbances and climate change will significantly decrease future streamflow by 61.91–112.16 m3/s on average, corresponding to a reduction of 14.08–25.51% from the baseline. We also suggest strategies to mitigate future water risks and enhance basin management in the MRB.