Since the impoundment and power generation of the Three Gorges project on June 1, 2003, river regime of the lower reach has experienced a great change. Up to 2006, the sediment runoffs at Yichang, Hankou and Datong are 0.0702, 0.134 and 0.163 billion tons, or 86%, 67% and 62% less than the mean annual values, respectively. Sediment grain size at all the hydrologic stations is coarsened,
... [Show full abstract] particularly at Jianli where an increase from 0.009 mm to 0.150 mm in grain size was observed. Meanwhile, bed erosion has been intensified significantly resulting in a lower water level. Between Yichang to Hukou where main channel erosion dominates, the erosion volume in the main channel below flood plain from Oct. 2002 to Oct. 2006 is 6.14 × 108m3. In comparison with 2002, the water level at Yichang after the flood season of 2006 is lowered by about 0.07 m and 0.49 m at flow rates 4000 m3/s and 10000 m3/s, respectively.