Abstract: Operation of the Three Gorges reservoir has caused changes in the natural hydrological regime. To evaluate the impact of the Three Gorges - Gezhouba cascade reservoirs on the middle Yangtze, we analyze the annual variation in water temperature at Yichang hydrological station, using statistical approaches of moving average, Kendall's rank correlation, and Spearman's rank correlation, and focusing on water temperature quantified with evaluation indicators. The results show that the Gezhouba reservoir has a slight impact on the water temperature at Yichang because of its small storage capacity. Since impoundment of the Three Gorges reservoir, water temperature has shown larger fluctuations featured with a hysteretic effect, and the peak-valley differences have decreased year by year. The impoundment has significantly impacted the natural river water temperature below the dam. The period of higher water temperature within a year has manifested a tendency of time delay, which is an evidence showing that the reservoir has caused changes in water temperature. Our analysis indicates that under this circumstance, the spawning time of Chinese sturgeon should have been delayed for about 29 days. This study would be useful to the ecological operation of the Three Gorges reservoir facing biological conservation.