Influence of the Three Gorges Project on Water Level in the Middle Reaches of Yangtze River, China

The alterations of the water level in the middle reaches of Yangtze River were investigated using the range of variability approach based on daily water level datasets extracted from 5hydrological stations.Results show that the operation of the Three Gorges Dam disturbed the hydrologic regime downstream and directly affected the water level to some extent. The rate and frequency of water level changes was most altered, while the timing of annual extreme water level was least affected. For the overall degrees of hydrologic alteration, high degrees were identified in Yichang (56%) and Jianli (47%) reaches; moderate degrees in Hankou (45%) reaches; and low degrees in Chenglingji (37%) and Luoshan (40%) reaches. Water level alterations in the middle reaches of Yangtze River were mainly caused by human activitiessuch as dam construction in the upstream and in-channel sand dredging, and also natural hydrological processes.