三峡水库蓄水运用初期长江中下游河道冲淤响应

根据来自长江水利委员会的2003年三峡水库蓄水前后出(入)库水沙变化的逐日数据(2003.5.25-6.12)以及长江中下游2003年和多年平均的干支流测站数据,本文对三峡水库蓄水初期长江中下游河道冲淤响应进行了初步研究。三峡水库蓄水后,拦沙作用十分明显,仅2003年6-12月份,水库淤积泥沙即达1.24亿t。由于泥沙被水库拦截,其下游各站输沙量均降低,河道沿程普遍发生冲刷(除监利至螺山段外)。各江段冲淤响应表现不一,从宜昌至监利冲刷量逐渐减小,监利至螺山段淤积,而从螺山到大通冲刷量逐渐增大。宜昌站至大通站间长江河道2003年总冲刷量为0.798亿t,比预测值小。三峡水库蓄水运用后长江河道冲淤形势发生的变化将对长江中下游环境带来一定的影响,加强及时的监测与研究十分必要。

Response of middle and lower reaches of Yangtze River to the initial operation stage of the Three Gorges Project

Based on the daily field data of flow and sediment at the inlet and outlet of the Three-Gorges Project(TGP) during the impoundment period (May 25 to Jun 12 in 2003), the measured data in the middle and lower reaches of the Yangtze River in 2003, and the multi-year statistical data from main stream and tributaries, the response of the middle and lower reaches of Yangtze River to the initial operation of the TGP is studied. TGP has an obvious effect to trap sediment and the total sedimentation reached 0.124 billion t during the period of Jun to Dec 2003. The low sediment-content water released from TGP caused long-distance erosion downstream the dam, except the Jianli-Luoshan reach. However, the erosion or deposition in different reaches exhibits different character. The erosion intensity gradually decreased from Yichang to Jianli, deposition was observed from Jianli to Luoshan, and the erosion from Luoshan to Datong increased slightly. Change of the channel bed variation after the operation of TGP will certainly bring either positive or negative effects. Therefore it is necessary to enhance the monitoring and study.