三峡水库蓄水运用以来库区泥沙淤积特性研究

Study of sediment deposition in region of Three Gorges reservoir after its impoundment

本文根据三峡水库蓄水运用以来实测水文、河道地形观测资料,对三峡水库进出库水沙变化和泥沙淤积特性进行了较为系统地分析,并将实测结果与三峡工程初步设计阶段、"九五"、"十五"攻关阶段的计算结果进行了对比,结果表明:2003年6月～2010年12月,三峡入库悬移质泥沙15.801亿t,出库悬移质泥沙4.118亿t,水库淤积泥沙11.683亿t。从淤积强度沿程分布来看,随着坝前水位的逐渐抬高,泥沙淤积呈上延趋势。从横向分布来看,泥沙淤积主要集中在主槽。从纵向分布来看,库区干流泥沙淤积以宽谷段(平均库区水面宽大于600m)为主,占全河段总淤积量的97.4%,窄深段淤积相对较少或略有冲刷。不同阶段水科院和长科院研究成果均表明,在三峡水库运用前10年大坝至丰都河段河床淤积最明显,由于各计算方案所采用的入库水文边界条件与蓄水运用后的实测水沙过程有一定的差别,引起各阶段研究库区年均淤积量较实测值偏大、近坝段的淤积强度较实测值偏小以及水库排沙比偏大等情况出现,但淤积量的沿程分布特性与实测值吻合较好。

This paper presents a systematic analysis of the flow and sediment variations and the sediment deposition in the Three Gorges reservoir(TGR) using the measured hydrologic and topographic data.This analysis indicates that from Jun.2003 to Dec.2010,the total inflow of suspended load was 1.58 billion tons,the total outflow 0.41 billion tons,and the sediment deposition 1.17 billion tons.In terms of its longitudinal distribution along the river,the deposition took a trend of gradually extending upstream as the water level at the dam was raised up.The deposition volume in the wide valley reaches of water surface wider than 600m accounted for 97.4% of the total,while the deposition in the other reaches was little or a slight scour appeared.As for its transverse distribution,the deposition was concentrated on the main channel.The results for different operation stages of TGR reveals that in the first 10 years of impoundment,the deposition in the reach from Fengdu to the dam was the most significant.Since the boundary conditions used by the numerical model for the impoundment stage were somewhat different from the measured ones,however,a difference existed between the predictions and measurements.A comparison shows that the predicted total deposition in the reservoir was larger,and the predicted deposition intensity near the dam and the predicted sediment diversion ratio were less than the measured values.Nevertheless,the predicted pattern of deposition distribution agreed with the measurements.