三峡工程对鄱阳湖冲淤的影响和预测

IMPACTS OF THREE-GORGE PROJECT ON EROSION AND DEPOSITION OF POYANG LAKE AND ITS PREDICTION

泥沙淤积是制约湖泊功能的重要因素。三峡工程运行后增减下泄流量,将使鄱阳湖的泥沙交换和淤积作用发生变化。本文根据鄱阳湖的沉积特点,利用典型年的水文过程对库区增减下泄流量时的冲淤变化进行了预测,指出直接的影响不大,但洲滩发展和束狭入江断面的负效应须有所警惕。

Silting-up is an important factor to have an impact on lake function. The increase or decrease of the discharge, after Three-Gorge Project goes into operation, will change the sand exchange and silt deposition in Poyang Lake. According to the sedimentary characters of Poyang Lake, this paper predicts the change in erosion and deposition with discharge by using the typical hydrological years, and the result shows that the biggest increasing range of silting up intensity is about 7. 2% in March-April, the decreasing range less than 1% in October and no change in other months. Assessment of erosion and deposition in the whole lake indicates that the sedimentary rate decreases a bit in the lake area to the south of Xinzi and increased by 0. 13 mm/a to the north. However, the range of erosion and deposition change is not the same as it in different years, which is related to the original lake level and the regulated level change near the outlet of lake. Its deposition rates, therefore, will tend to be low. It proves that there will be less change in lake sedimention and erosion rate after Three-Gorge Reservoir goes into operation. However, the negative effects of river beach development and the lake outlet section narrowing should be paid vigilant attention to.