Relation between adjustment of the low water level-riverbed shape and utilization of the water depth in the Shashi Reach in the middle reach of the Yangtze River

The Shashi Reach is in the upper Jingjiang Reach in the middle and upper reaches of the Yangtze River. Over the years, it has been a critical river section for channel management and maintenance, of which the relationship between the change of the low water level and the utilized use of channel water depth has always been a hot issue. This paper firstly collected the hydrological, sediment, bathymetry data of this reach from the year 1975 to 2018, and then studied the characteristics of the low water level change and its impact on the utilization of the water depth for navigation. The results show that during the period of 1975 to 2018, the riverbed in the Shashi Reach has been greatly scoured and incised, and the overall cross – sectional profiles of this reach has become narrowing and deepening, which provides a good potential to improve the water depth of the channel. In terms of making the utilization of the channel water depth, the continuous scouring of the river channel would result in the decrease of the discharge at the Taipingkou mouth, which is conducive to the improve the water depth conditions of the channel during the dry season in the Shashi Reach. Under the action of a series of channel regulation projects, the 3.5m isobaths of the Shashi reach would be basically unobstructed, thus from this point of view, it is favorable to select from the South Taipingko Channel to the North Sanbatan Channel as the main navigation channel during the dry season. Taking into account factors such as the current water depth and the clear width limitation of the navigation hole of the Jingzhou Yangtze River Bridge, the route from the South Taipingko Channel to the North Sanbatan Channel can still be selected as the main navigation channel during the dry season for the 4.5m depth channel.