小浪底水库运用初期支流泥沙淤积特征分析

Analysis of Characteristics of Sediment in Tributaries During the Initial Operation Period of Xiaolangdi Reservoir

小浪底库区支流倒灌形成泥沙淤积,而其淤积形态和淤积物组成与干流河床形态、水库运用方式、来水来沙条件等因素密切相关。水库水位抬升,干流浑水倒灌支流并沿程落淤,支流沟口淤积与干流同步抬升,沟口以上淤积厚度沿程减小。随着淤积的发展,支流的纵剖面形态不断发生变化,总的趋势是由正坡至水平而后出现倒坡。支流内淤积物组成与对应的主槽位置差别不大,随着运用时间的增加及淤积形态的变化,入库水流携带泥沙进入变动回水区后沿程分选,支流内淤积物组成随之产生一定变化。拦沙初期阶段,近坝支流淤积物自下而上发生粗化,远坝支流淤积物则比较复杂,靠沟口位置变化幅度不大,再向上游则呈现逐年细化态势。

Due to water intrusion to the tributaries in Xiaolangdi Reservoir,there is sediment deposition in the tributaries that deposition morphology and sediment composition are closely related to the riverbed form of main stream,the operation schemes of the reservoir,the factors of sediment-lad-en flow and so on. As the rise of reservoir water level,the muddy water flows backward from main stream to tributaries and silts along the stream, siltation of tributary outlets synchronously lift with main stream,the siltation thickness of sediment deposition upstream from the outlet decreases a-long the stream. With the development of sedimentation,the longitudinal profile of tributaries varies constantly,and it generally trends from positive slope to level ,and then to adverse slope. The sediment composition in tributaries has little difference from that in the corresponding main channel. Along with the increase of using time and the variation of deposition morphology,the water flow that carries sediment and flows into the reservoir sorts along the stream after it flows into the backwater catchment,and with this,the sediment composition in the tributaries has some changes. Dur-ing the initial operation period,the sediment of tributaries in the vicinity area of dam becomes coarse from upstream to downstream,while the sedi-ment of tributaries far from the area of dam is relatively complicated. But near the outlet,the change is not obvious,and it appears trend of refining year by year.