Multi-model ensemble of precipitation changes of the Pearl River Basin and its impact to the water resources

Pearl River Basin is the second largest river in China based on its water quantity, its water resources is very important to the regional developemnt, but its response to climate change has not been well studied. In this study, the projected precipitation of Pearl River Basin from 25 Coupled Model Intercomparison Projection phase 6 (CMIP6) are abstracted first, and multi-dimensional metrics for evaluation has been calculated based on the historical (2001-2014) precipitation observation basin wide. Based on the comprehensive performance, an ensemble precipitation of the basin is constructed, and the future precipitation changes during 2025-2100 is investigated under three scenarios (SSP1-2.6, SSP2-4.5, and SSP5-8.5). The results showed that the CMIP6 models underestimated the precipitation over the basin but the consistency is reasonable, the annual precipitation exihibtes a significant increase trend under three scenarios from 2025 to 2100, spatially the precipitation in most area of the basin show a steady increase in the middle and the end of the 21st century. By employing the SWAT hydrological model, the runoff changes in the near-term (2025-2045), medium­ term (2045-2064), and terminal (2087-2700) have been simulated based on the above projected precipitation. Results shows that the runoff in the basin shows an increasing trend, and the growth rate of runoff increases with the increase of emission scenarios. Except for the low emission scenario where runoff decreases in the middle of the 21st century compared to the base period, runoff increases in the rest of the scenarios and periods relative to the base period.