Acta Geographica Sinica ›› 2017, Vol. 72 ›› Issue (7): 1184-1194.doi: 10.11821/dlxb201707005

• Orginal Article • Previous Articles     Next Articles

Response of low water level change to bed erosion and the operation of Three Gorges Reservoir in upper Jingjiang reach

Lingling ZHU1(), Xia YANG2, Quanxi XU1   

  1. 1. Bureau of Hydrology, Changjiang Water Resources Commission, Wuhan 430010, China
    2. Three Gorges Construction and Operation Management Department, Yichang 443133, Hubei, China
  • Received:2016-12-05 Revised:2017-02-23 Online:2017-08-07 Published:2017-08-07

Abstract:

The upper Jingjiang reach, which is located at the beginning of sandy channel downstream from the Three Gorges Reservoir (TGR), is undergoing continuous erosion. As a response to riverbed erosion, there has been an obvious water level drop during the dry seasons in the past decades. And this phenomenon has drawn much attention because of its close connections with irrigation, navigation, water environment, dike safety, and so on. In this article, by using the reorganized data of the gauging stations, elaborate efforts were made to examine the characteristics of the low water level in upper Jingjiang reach, including the variations in the same discharge, the same stage and the annual minimum. Besides, the impacts of the TGR operation in dry seasons were also analyzed. This operation mainly refers to the increase of the water release from TGR when its water level almost reached 175 m, which was to ease the drought-prone downstream since 2009. The results show that: (1) the drop of the water level in the discharge of 7000 m3/s were 0.59 m and 1.64 m at Zhicheng and Shashi gauging stations from 2003 to 2015, respectively. On the contrary, the lowest water level has been raised, and the duration of extremely low water level has been reduced since the impoundment of TGR; (2) The drop of low water level was evidently affected by the river bed erosion at Shashi gauging station. The drop of its low water level and the erosion of the nearly river bed were found to be of almost the equal magnitude. However, a smaller drop of low water level at Zhicheng gauging station has arisen, under the comprehensive influences of channel morphology, river bed armoring and channel regulation works; (3) The compensation operation of TGR in dry seasons can raise the monthly-averaged water level from January to April by increasing its water release. In addition, the annual lowest water level was raised, and the extremely low water level duration has been reduced. However, such compensation still cannot eliminate the impact of river bed erosion at Shashi station, even if the compensating discharge reached 2000 m3/s.

Key words: upper Jingjiang reach, low water level for same discharge, low water level, annual lowest water level, compensation operation of TGR in dry season