筑坝拦截对黑河河道沉积物粒度空间分布的影响

Effects of dam interception on the spatial distribution of sediment granularities in Heihe River

河流沉积物对流域环境变化具有敏感响应,其粒度参数能反映沉积环境中物质来源和水动力环境.本文以黑河流域上中游为研究区域,探究河流沉积物粒度对流域环境变化的响应.从黑河上中游干流22个主要控制断面采集河床沉积物样品,采用筛分法和吸管法对沉积物样品粒度参数进行测定,并分析其空间分布规律对筑坝拦截为主的环境改变响应.研究结果表明:受梯级水库建设影响,黑河上中游泥沙粒径大小差异显著.干流库区泥沙粒径较自然河段明显减小,分选很好,呈正偏或极正偏尖锐分布,而且在库区不同沉积高度上表现出分层沉积特征;坝下游河段因遭受强烈冲刷,较自然河段泥沙粒径粗化显著,分选变差,偏态趋向极正偏,峰态尖锐化;水库回水区受水库壅水及下泄清水的双重制约,泥沙粒度参数介于自然河段和坝下游河段之间,整体分选中等,呈极正偏尖锐分布;沉积环境分析表明,上游支流河段沉积物粒度特征受泥沙供给和物源特征的影响较水动力条件显著,干流河段沉积物粒度特征主要受水动力条件控制.研究结果既符合河流上中游沉积物粒度分布规律,也反映了河流环境变化对沉积物粒度组成的影响.

River sediments respond sensitively to the basin environmental changes and particle size parameters can reflect the material sources and hydrodynamic environment.This article takes the Heihe River as a case to explore the response of river sediment grain size to the basin environmental changes.River sediment samples were collected from 22 sections along the mainstream of the Heihe River.Then,sieving and pipette methods were applied to measure the particle size.Spatial variations of grain size parameters and their responses to the anthropogenic environmental changes of the basin through river damming were analyzed.The results showed that the grain size of the upper and middle reaches of Heihe River was significantly different under the influence of the construction of cascade reservoirs.The grain size of reservoir sediment decreased more obviously in the river section within cascade reservoirs than in the original natural reach,and the sediments are characterized by well-sorted,with acute kurtosis and positive skew or very positive skew.In addition,the sediment grain size shows the characteristics of layered sedimentary at different depositional heights in the reservoirs.The downstream river of the Dam was suffering from strong erosion,and the grain size of bed sediments is coarse and poorly sorted,and the grain size distributions are more positively skewed with sharp kurtosis.The backwater area of the reservoir is restricted by backwater and drainage water,and the sediment particle size is between the original natural river and the downstream river of the dam,with middle sorted sediments,positively skewed grain size distribution and acute kurtosis.Sedimentary environment analysis reveals that the sediments grain size characteristics of upstream tributary are more influenced by material sources than hydrodynamic conditions,while the grain size characteristics of main stream sediments are mainly controlled by hydrodynamic conditions.The results are consistent with the normal pattern of sediment grain sizes distribution in rivers,and also reflect the impact of environmental changes on river sediment grain size composition.