River flow and sediment concentration changes in the Wu-Xi River, central Taiwan, under CMIP6 scenarios

Abstract

This study evaluates river flow and sediment changes in the Wu-Xi River in central Taiwan, simulated by SWAT+ under Coupled Model Intercomparison Projection Phase 6 (CMIP6) climate change scenarios. The model is calibrated and validated with historical observations, and 24 CMIP6 models are selected to simulate future river flow and sediment concentration. The results indicate that the exceedance probability of 100-year river flow may increase approximately threefold in the near future (NF) (2031-2050) and tenfold by the end of the century (EC) (2081-2100) in the worst scenario (SSP585). Under the low-emissions scenario (SSP126), it increases twofold in the NF and 3.6-fold by the EC. Mean sediment concentration is projected to rise by 4.6% in the NF and 22.7% by the EC in the SSP585 scenario. Model performance is weaker in the upstream area, where highly dynamic flow and sediment responses are difficult to reproduce due to sparse rain-gauge coverage and limited soil detail in the mountainous area. Despite these limitations, the insights in this study are valuable for water agencies for further safety evaluation of the river protections in the downstream area of the Wu-Xi River.