紫坪铺水库运用以来泥沙淤积特征分析

Analysis of Sedimentation Characteristics of Zipingpu Reservoir Since Its Operation

紫坪铺水库是都江堰灌区和成都市最重要的调节水源、成都市最重要的支撑电源,为全面掌握其泥沙淤积现状,基于库区实地调研、大断面观测资料和逐年水位观测资料等,对该水库运用以来的调度运用方式、泥沙淤积形态、泥沙淤积分布以及淤积物颗粒组成等进行了分析。分析结果表明:截至2020年10月,紫坪铺水库淤积总量为1.952亿m^(3),拦沙库容淤损87.1%,其中干流淤积量为1.843亿m^(3)、支流淤积量为0.109亿m^(3);受2008年汶川地震影响,该水库年均淤积量由地震前的0.088亿m^(3)增大至地震后的0.137亿m^(3),严重影响了水库的功能和寿命;淤积泥沙的95.0%集中在距坝16.32 km的M31断面以下库区,淤积泥沙的85.1%分布在850 m高程以下库区;淤积物中黏粒、粉细沙、中粗沙及卵石分别占淤积物总量的19.5%、73.0%、7.5%。建议尽快实施人工清淤疏浚,以恢复水库拦沙库容。

Zipingpu Reservoir is the most important source of water regulation in Dujiangyanirrigation area and Chengdu City,and the most important source of support for Chengdu City.In order to fully grasp the current status of sedimentation,based on field investigations,large-section observation data and year-by-year water level observation data in the reservoir area,it analyzed the operation mode of the reservoir since its operation,the silt deposition form,the distribution of silt deposition and the composition of silt.The analysis results show that as of October 2020,the total amount of siltation in Zipingpu Reservoir is 195.2 million m^(3),and the sediment retention loss of storage capacity is 87.1%,of which,the siltation volume of the main stream is 184.3 million m^(3)and the siltation volume of tributaries is 10.9 million m^(3);Influenced by the Wenchuan earthquake,the average annual siltation volume of the reservoir is increased from 8.8 million m^(3)before the earthquake to 13.37 million m^(3)after the earthquake,which seriously affects the function and life of the reservoir;95.0%of the siltation is concentrated on the M31 section which is 16.32 km away from the dam.85.1%of the sediment is deposited in the reservoir area below the elevation of 850 m;clay,silt and fine sand,medium-coarse sand and pebbles in the silt account for 19.5%,73.0%and 7.5%of the total silt respectively.It is recommended that manual dredging should be implemented as soon as possible to restore the reservoir’s sediment holding capacity.