三峡水库175m蓄水后库尾河段减淤调度控制指标研究

重庆主城区河段河道泥沙冲淤事关防洪、航运及码头作业等,是三峡水库泥沙问题的重点内容之一。本文依据原型观测资料,以三峡水库175 m试验性蓄水前后河段的泥沙冲淤规律为基础,结合河床组成分析和一维数学模型,计算提出河段悬移质泥沙走沙基本条件,并应用于减淤调度实践中。结果表明：① 三峡水库175 m试验性蓄水后至2012年重庆主城区河段河床冲刷强度下降,主走沙期推迟至汛前消落期,2013年后上游来沙减少使得河床冲刷强度再次增大;② 当寸滩站流量大于4000 m ³/s、坝前水位低于167 m时,河段开始走沙;当寸滩站流量增大至超过5000 m ³/s、坝前水位下降至163 m时,河段走沙能力增强;加大水库自163 m水位的消落速度,能够避免库尾河段产生累积性淤积。

Control index of sediment reduction dispatching in Chongqing reach after the storage level of TGR reaching 175 m

Chongqing reach is located in the fluctuating backwater zone of the Three Gorges Reservoir (TGR). Sediment deposition and erosion of Chongqing reach is related to flood control, shipping and wharf operation. It has become one of the key problems the TGR faces. In this paper, based on the prototype observation data, the sediment scouring and silting law of Chongqing reach before and after the 175 m experimental impoundment of the TGR was investigated for the first time. In addition, combined with the analysis of river bed composition and the one-dimensional mathematical model, the scouring conditions of suspended sediment in Chongqing reach were calculated and analyzed. Furthermore, the basic conditions of sediment transport in the study reach were applied to the practice of sediment reduction of the TGR. The following conclusions can be drawn as follows: (1) From 2008 to 2012, when the water storage level of TGR reached 175 m, the erosion intensity of the river bed in Chongqing reach started to decline, and the main souring period of suspended load was postponed from the water-impoundment stage to the pre-flood stage. After 2013, Xiluodu and Xiangjiaba hydropower stations in the lower reaches of Jinsha River was completed and put into operation. The sediment of Jinsha River was intercepted and the sediment entering the Three Gorges was greatly reduced, which led to another increase of the river bed scouring intensity of Chongqing reach. (2) When the inflow in front of the Three Gorges Dam (TGD) is greater than 4000 m ³/s and the water level is lower than 167 m, the suspended load on the river bed in Chongqing reach begins to scour. When the inflow exceeds 5000 m ³/s, the water level in front of the TGD drops to 163 m, and the scouring intensity of suspended load increases obviously. Increasing the drawdown rate of water level from 163 m before the TGD to 30 cm per day can avoid the cumulative sedimentation in the Chongqing reach.