Abstract: The entire Yangtze River basin has witnessed continuous high temperature and drought to various degrees in the flood season of 2022, which has presented daunting challenges to the regulation of cascade reservoirs in the upstream of Yangtze River. To address the issue of water storage within the cascade reservoir group during drought conditions, we selected the flood control reservoir group in the upper reaches of the Three Gorges as the research object and propose indicators including the water level at the end of flood season, the storage fullness, and the impoundment rate to analyze the water storage process and storage fullness trends over the past decade.On this basis,according to the water inflow patterns and its distribution among different regions during typical historical dry years,we examined the water storage situation and the completion rate of water storage tasks during the impoundment period under different drought conditions. Specifically, we elabrated on the degree of understorage (the degree of not fullfilling storage tasks) in the presence of varying frequencies and regional distributions of water inflow. The findings reveal that when the frequency of inflow surpasses 80%, the fourteen cascade reservoirs assessed in this study successfully fulfill the storage tasks in September and October. However, when the frequency of inflow falls below 90%, the cumulative shortfall within the cascade reservoirs amounts to 16.55 billion m³. This observation offers risk analysis support for efficient water resources utilization within the basin by revealing the water storage situation of the cascade reservoirs in the upper reaches of Three Gorges during drought conditions similar to those experienced in 2022.

Key words: cascade reservoirs, water storage situation, drought conditions, degree of understoage, upperstream of the Yangtze River