Abstract
After Three Gorges Reservoir building up, the natural river course and the near hillside inside the backwater region are inundated to form a fairly wide man-made lake which affects the hydrological characteristics and floodwater transmission to different degrees. When the reservoir impound to high water level, the conflux time is obviously shortened, the flood-peak discharge increase, and the peak type became sharper. The change of runoff yield and concentration makes the forecast scheme unable to be applied well. Based on the practice of Three Gorges Reservoir operation, the rainfall-runoff characteristics of the backwater region under the condition of high water level are analysed and summarized, then a set of unit hydrographs suitable for rainfall-runoff calculation are recalibrated, which has great reference value for hydrological forecasting of Three Gorges region.
Highlights
Three Gorges Reservoir is a key project in the Yangtze River basin
The natural river course and the near hillside inside the backwater region are inundated to form a fairly wide man-made lake, which cause the behaviour of rainfall generation and influx are bound to change[2]
Part of the rainfall in the reservoir area falls directly on the surface of the water, and some of it is quickly collected into the reservoir after generation and influx
Summary
Three Gorges Reservoir is a key project in the Yangtze River basin. The autumn flood in recent years show that, with the rise of water level, the law of rainfall concentration and channel flood propagation has changed greatly in the backwater area of the reservoir. The natural river course and the near hillside inside the backwater region are inundated to form a fairly wide man-made lake, which cause the behaviour of rainfall generation and influx are bound to change[2]. The forecast earliness of flood in this region is short, and the flood peak is sharp and the flood volume is large, which is a major factor restricting the real-time dispatch of Three Gorges Reservoir. For the situation that the change of hydrological conditions in the reservoir area makes the original prediction scheme unable to be applied well, this paper analyzes and summarizes the characteristics of rainfall runoff in the reservoir area under high water level, and redefines a set of unit lines suitable for high water level, in order to calculate dynamic inflow as a result of heavy rainfall, which has great reference value for improving the accuracy of hydrological forecasting in the backwater region of Three Gorges Reservoir
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