Water and sediment regulation in past two years at upper and middle Yellow River

Drawdown flushing in reservoirs is a key scheme for reservoirs water and sediment regulation in Yellow River basin, making it possible to maintain the effective storage capacity of the reservoirs. In early September of 2023 and 2024, joint operation of key reservoirs in the upper and middle reaches of the Yellow River was carried out to implement sediment discharge. In 2023, the water and sediment regulation resulted in an outflow of 610 million m³ from Liujiaxia Reservoir. Four reservoirs, including Qingtongxia, Haibowan, Wanjiazhai, and Longkou, discharged a total of 75 million tons of sediment, consuming 8 m³ of water per ton of sediment. In 2024, the water and sediment regulation resulted in a water output of 1.09 billion m³ from Liujiaxia Reservoir. The five reservoirs of Shapotou, Qingtongxia, Haibowan, Wanjiazhai, and Longkou Reservoirs discharged a total of 144 million tons of sediment, consuming 7.5 m³ of water per ton of sediment. Through the practice of water and sediment regulation, it has been proven that flushing is a systematic response of reservoir deposition to the drawdown of water level. The flushing process is unsteady, and the sediment concentration at the outlet increases rapidly at first and then decreases rapidly. The scouring amount is positively correlated with the magnitude of inflow discharge and duration of drawdown. The larger the discharge, the longer the duration, and the more sediment discharge.