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用人工断面法和流量堰法测流,高密度采集水样,在室内用称重法测得水体含沙量,对大龙洞地下河出口及其邻近地表河、地下河上游地表河段进行同步输沙特征监测,以为拟建的大龙洞水库泥沙淤积评价提供依据。两个水文年的研究结果均显示,地下河与地表河输沙率呈同步变化特征,平均悬移质输沙模数分别为37.26～58.33t/km2·a和56.82～76.80t/km2·a,最大日平均输沙率分别为540mg/L和890mg/L,说明地下河空间以大型岩溶管道为主,连通性好,系统水力坡度大,对泥沙输出和减轻地下空间淤积有利。最大日平均输沙率均与最大流量峰值对应,说明水土流失主要发生在暴雨期间。选择流域内三种典型生态环境类型,进行原位水土流失观测,获得场雨产流过程和坡面流输沙率变化情况。结果显示,三种类型的平均悬移质输沙模数为65.35～884.78t/km2·a,暴雨期间准森林类最大瞬时输沙率为2926mg/L。在此基础上,估算得到在建库条件下50年总淤积量不超过地下库容的10%,说明水土流失造成的水库淤积程度并不严重。
Using artificial cross-section method and flow weir method to measure flow, high-density water samples were collected, indoor sediment concentration was measured by weighing method, and the surface drainage of Dalongdong underground river and its adjacent surface river and upstream surface river were synchronized Sediment characteristics monitoring, in order to provide the basis for the evaluation of sediment deposition of the dam of Dalongdong Reservoir. The results of the two hydrological years show that the sediment transport rates of underground rivers and surface rivers show synchronous characteristics, and the average suspended sediment transport modulus are 37.26 ~ 58.33t / km2 · a and 56.82 ~ 76.80t / km2 · a , And the maximum daily average sediment transport rates are 540mg / L and 890mg / L, respectively. This indicates that the underground river space is dominated by large-scale karst pipelines. It has good connectivity and large hydraulic slope. It is good for sediment output and sedimentation reduction of underground space. The maximum daily mean sediment transport rate corresponds to the peak of maximum flow rate, indicating that soil erosion mainly occurred during the heavy rain. Three types of typical ecological environment in the basin were selected to observe in-situ soil and water loss, and the changes of the runoff rate during runoff and slope runoff were obtained. The results show that the average suspended sediment transport modulus of the three types is 65.35 ~ 884.78t / km2 · a, and the maximum instantaneous sediment transport rate of quasi-forest is 2926mg / L during the heavy rainfall. On this basis, it is estimated that the total siltation within 50 years under the reservoir construction conditions will not exceed 10% of the underground storage capacity, indicating that the degree of reservoir siltation caused by soil erosion is not serious.