Analysis of Siltation Characteristics of Xiluodu Reservoir

Abstract: Xiluodu Hydropower Station is located in the lower reaches of the Jinsha River in the southwest mountainous area of ​​China, with the fourth largest hydropower station in the world. The maximum dam height is 278m and the total installed capacity is 12.6 million kW. The China Three Gorges Corporation has paid close attention to the reservoir siltation after the Xiluodu Reservoir was built. A series of hydrological and sediment monitoring work was carried out during the reservoir construction and operation from 2008. Xiluodu reservoir has three main tributary (Meigu River, Xixi River and Liulanjiang River). Based on the topographic (fixed section) data of the Xiluodu reservoir area from February 2008 to November 2017, the siltation characteristics of the Xiluodu reservoir was calculated and analyzed. The results show that between February 2008 and November 2017, the mainstream and tributaries of the Xiluodu Reservoir had silted up to 48.224 million m³. Among them: the fluctuating backwater reach (Baihetan dam site to Duiping Town, about 36.0km) and the perennial backwater reach (from Duiping Town to dam site, about 159.1km), silted sediment 28.34 million m³ and 453.9 million m³ , accounting for 5.9% and 94.1% of the total siltation, respectively. The deep point of the reservoir area increased by an average of 12.6m. While, the sediment gradation and dry bulk density of sediment decreased along the path, and the average dry bulk density was 0.78t/m³, the sediment gradation and dry bulk density are positively correlated. But, siltation calculated by sediment transport method is 51.439 million tons, and that is 31.704million tons by the sediment transport method. However, due to the storage and sediment retention of the upstream cascade reservoirs, the amount of sediment transported by the Xiluodu Reservoir has been greatly reduced by 98%. The measured sedimentation volume in the reservoir area is smaller than that in the study stage. And the siltation of the Xiluodu Reservoir will be further reduced with the impoundment of the upstream reservoir.