Effect of Baige landslide-dammed lake on runoff and sediment of the Jinsha River and operation of cascade reservoirs

Baige landslide occurred in the upstream of Jinsha River in October 10, 2018 caused the most serious river blockage event in the recent hundred years. Formation and breaking of the Baige landslide-dammed lake (BLDL) had unknown effects on water and sediment conditions and the operation of cascade hydropower stations in the main stream of the downstream Jinsha River. Based on the observational data of the temporary gauge station near the BLDL and the controlled hydrological stations in the main trunk of Jinsha River, the effects of BLDL on water and sediment conditions in the middle and lower Jinsha River are studied. Combining with the operation of cascade reservoirs before and after the breaking of the landslide-dammed lake, the sediment retention amount of cascade reservoirs is estimated. The results showed the breaking of the BLDL formed a super-historical hydrograph of water and sediment in the middle Jinsha River. After the emergency regulation of cascade reservoirs in the middle Jinsha River, the extraordinary flood caused by the outbreak of the BLDL was reduced to a normal flood. Nearly 26% of the sediment generated by landslides is transported and deposited in cascade reservoirs in the middle Jinsha River. Among them, the Liyuan, Ahai, and Jinanqiao hydropower stations intercepted about 14 million tons of sediment, while Longkaikou, Ludila, and Guanyinyan hydropower stations intercepted about 0.43 million tons of sediment. About 74% of the landslide-induced sediment remains near the Baige barrier. Given that all the sediments generated by the Baige landslide are transported into the cascade reservoirs along the middle Jinsha River, the effective reservoir capacity of Liyuan hydropower station will probably not meet the requirement of the reservoir regulating capacity. © 2020 by Journal of Lake Sciences.