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Archive > Volume 22 Issue 6 > 2024,22(6):1129-1136 Prev Next

Impact of Xiaolangdi Reservoir on the water and sediment processes in the lower reaches of the Yellow River

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    Abstract:
    The construction of cascade reservoirs is a trend and inevitable way for efficient utilization of water resources in the basin. At the same time, the construction and operation of reservoirs have led to the redistribution of non-biological elements such as water and sediment, resulting in changes in the structure and function of river ecosystems. Multiple reservoirs often produce various effects such as summation, synergy, and antagonism along with a complex ecological impact especially in cascade development. The impact of adding new reservoirs has become a key factor in the planning of river cascade development. The river ecosystem is influenced by multiple factors such as water conservancy engineering conditions, climate change, land use, and water intake, which raises difficulty for scientifically quantitfying the role of newly added reservoirs. Xiaolangdi Reservoir is a critical project for controlling the water and sediment processes in the lower reaches of the Yellow River, and since its scheduling, it has jointly worked in conjunction with Sanmenxia Reservoir. Since the scheduling of the Xiaolangdi Reservoir, there have been significant changes in the water and sediment processes in the lower reaches of the Yellow River. To quantify the role played by the Xiaolangdi Reservoir in these changes, the changes in water and sediment conditions in the lower reaches of the Yellow River during the single reservoir period of Sanmenxia Reservoir and the dual reservoir period of Sanmenxia Reservoir and Xiaolangdi Reservoir are quantified. The impact of Xiaolangdi Reservoir is quantitatively evaluated through methods such as trend testing, abrupt change point analysis, and numerical simulation. The results show that the single reservoir period compared with the joint scheduling of Xiaolangdi Reservoir and Sanmenxia Reservoir shortened the duration of low flow events in the lower reaches of the Yellow River, prolonged the duration of high flow events, and caused continuous erosion of the river channel. Compared with the single reservoir period, at the three cross-secions of Huayuankou, Gaocun, and Lijin during the dual reservoir period: the average number of days below the warning flow decreased by more than 90%, and the average number of days above3000 m3/s increased by more than 85%; the duration of high flow pulses during the critical period of fish reproduction (April to June) increased by more than 50%; the annual average sediment yield and average sediment concentration have decreased by more than 70%; the main groove of the cross-sections was deepened and the elevation was reduced. The role played by Xiaolangdi Reservoir was consistent with the characteristics of changes in water and sediment processes. The scheduling of Xiaolangdi Reservoir increased the number of days with a flow greater than 3000m3/s by 86%, and reduced the number of days with a flow less than 150 m3/s by 57%. Xiaolangdi Reservoir annually retained an average of 1.50×108m3 of sediment. The sudden change time of sediment concentration at Huayuankou cross-secion is consistent with the operation time of Xiaolangdi Reservoir. Without Xiaolangdi Reservoir, the the lower reaches of the Yellow River would have shifted from an average annual erosion of 130 million t to an average annual sedimentation of 28 million t. After the joint scheduling of Xiaolangdi Reservoir and Sanmenxia Reservoir, the ecological base flow guarantee rate and habitat stability in the lower reaches of the Yellow River have been improved, and the diversity of freshwater fish has been effectively restored.

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