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How to utilize the joint operation of reservoir groups to maximize sediment discharge efficiency is a key technical challenge in water and sediment regulation. This paper selected the joint operation of Sanmenxia and Xiaolangdi reservoirs in the period of water and sediment regulation in 2023 as the object, analyzed the water and sediment processes of the two reservoirs under different matching opportunities and matching water levels, and quantified the water and sediment regulation effect under different matching opportunities and matching water levels between the two reservoirs. Although the Sanmenxia Reservoir has a smaller water storage capacity and limited water transfer capacity, by changing the discharge time of the reservoir, the scouring effect of Xiaolangdi Reservoir is quite different. As the matching water level decreases, the amount of erosion in the reservoir area gradually increases. With the delay of the relative discharge time of Sanmenxia Reservoir, the erosion amount in the reservoir area shows a trend of first increasing and then decreasing. [ABSTRACT FROM AUTHOR]

Xiaolangdi Reservoir is the key project of flood control and security in the lower reaches of the Yellow River, and the sediment retention period of the reservoir is the most significant period for flood control and sediment reduction benefits. This paper analyzed the new requirements for flood control and security of Xiaolangdi Reservoir under the new situation of the lower reaches of the Yellow River, and pointed out that it was of great strategic significance to extend the sediment retention period of Xiaolangdi Reservoir as much as possible, so as to maintain the effective storage capacity of the reservoir as long as possible, especially the flood control storage capacity. The research shows that the larger reservoir capacity has a strong ability to deal with large floods, which is conducive to the prevention of “black swan” events; after the flood control operation of the reservoir, the loss of the beach storage capacity is small, which is conducive to the long-term maintenance of the reservoir’s strong flood control capacity; the combination of sediment storage capacity and water and sediment regulation capacity can significantly enhance the vitality of water and sediment regulation, and create storage conditions for the Guxian Reservoir to exert the overall joint force of the water and sediment regulation system after putting into operation; the use of the sediment storage capacity for flood control in the downstream beach area is conducive to improving the flood control standard of the beach area and reducing the loss of the beach area in the normal flooding. Optimizing the operation mode of reservoir operation, implementing reservoir dredging and building Guxian Water Control Project as soon as possible are important measures to extend the sediment retention period of Xiaolangdi Reservoir. [ABSTRACT FROM AUTHOR]

The joint operation of Xiaolangdi Reservoir with Sanmenxia Reservoir and tributary reservoirs after the completion of Xiaolangdi Reservoir marks the basic completion of the downstream flood control and disaster reduction project system. However, for the Yellow River beach area, which has always been emphasized as the space for flood detention and sediment deposition, the reservoir flood control operation has set the goal of ensuring that the beach area is not filled with water for many years. Taking the autumn flood in recent four years, including 2021, as an example, this paper showed that it was more difficult to block and stagger the peak of the reservoir after the superposition of a variety of adverse factors, especially when the inflow of trunk tributaries was encountered. In order to solve this problem, it was considered that under the specific restriction of Huayuankou flow. Sanmenxia Reservoir should be allowed to stop the flood, transition to the non flood season pool level in advance, help Xiaolangdi Reservoir reserve the storage capacity under the maximum allowable water level, and skillfully stagger the flood discharge. When necessary, the temporary storage water level of Sammenxia Reservoir could break through to reduce the safe ty risk of high water level of Xiaolangdi dam. In addition, under the current situation that the amount of sediment entering the reservoir de creased greatly. The operation mode of Sanmenxia Reservoir should be adjusted and improved, strive to make this pearl of the Yellow River shine again, improve the downstream flood control engineering system, give play to the role of optimizing the allocation of water resources, and provide safety guarantee for downstream flood control, disaster reduction and high-quality development. [ABSTRACT FROM AUTHOR]