The increasing risk of future simultaneous droughts over the Yangtze River basin based on CMIP6 models

Drought projection is critical for water resource planning and management, as well disaster prevention mitigation. As a strategic national source China, the Yangtze River Basin (YRB) plays vital role in connectivity of rivers economic development, flowing through 11 provincial administrative regions injected into East China Sea, with total length 6,397 km. The watershed covers an area 1.8 million square kilometers, accounting about 1/5 China's land area. However, frequent droughts have caused shortages YRB recent years. Based on observed meteorological hydrological data, CMIP6 model SPEI (standardized precipitation evapotranspiration index) drought models were used to elucidate risk future simultaneous upper mid-lower reaches from 2015 2100. SRI has been based SWAT study transfer process drought. results indicated that, (1) average 10 showed good verification historical temperature predictions. MMK Sen’s slope demonstrated consistency YRB. From perspective (1961–2019), middle experienced intensifying frequency highest (Moderate above events) (> 17%); (2) In (2020–2100), higher emission signifies moderate frequency, intensity, scope FF, lower NF. ratio autumn severe extreme would increase mid-twenty-first century; (3) Severe encounters projected meanwhile middle-lower YRB, especially 2030–2040 period. Under all three scenarios, occurred more frequently close − 2. are forecast witness largest intensity under SSP1-2.6 scenario.; (4) runoff during dry period varied less, but May June main flood season be largest. Maximum decrease SSP2-4.5 scenario 2045, reaching 13.9%. Extreme flooding events happen accompanying occur severely different scenarios. More attention improved strategies should brought bear address