Abstract: Chongqing reach is well known as the land and water transport hub in southeast China. Sediment erosion and deposition in Chongqing reach, as related to flood control, navigation and dock operation, is a core issue in the demonstration phase of Three Gorges Reservoir (TGR). Since the water level in front of Three Gorges Dam reached 175 m, the hydraulic characteristics and sediment erosion and deposition in Chongqing reach, as the tail area of the TGR, has changed prominently. According to prototype observation data, the sediment scour and silting in Chonqing reach from 2003 to 2016 when the water level in front of Three Gorges Dam increased from 145 m to 175 m was compared and analyzed. Results showed that in natural condition, sediment erosion dominated the Chongqing reach, with sediment always silting in flood season and scouring after flood season. From 2009 to 2012, the intensity of river bed scour in Chongqing reach decreased, and the erosion period delayed to seasons before flood of the next year. As sediment yield greatly declined after the operation of cascade hydropower stations in the lower Jinsha River, scour is very likely to occur again in Chongqing reach. The research results are expected to provide reference for the operation of TGR and the planning and regulation of Chongqing reach

Key words: Three Gorges Reservoir, Chongqing reach, sediment erosion and deposition, 175 m experimental water storage level, main sediment erosion period, incoming sediment