Great Changes on Flood Control of Lower Yellow River after Operation of Xiaolangdi Reservoir

Abstract Representing the most important influence on the land-ocean sediment fluxes in the world, dams and reservoirs alter the continuity of sediment transport and decrease the supply of sediment to downstream reaches. After the operation of Xiaolangdi Reservoir, channel bed of the lower Yellow River has been strongly eroded, and the discharge capacity increased gradually. In recent decades, the trend of flow and sediment alters due to the massive harnessing projects on the upper and middle reaches. The amount of sediment entering the lower reach has been gradually reduced significantly, and there are no big flood events. There are no floods exceeding the warning water stage, thus the flood control situation of the downstream reach has changed dramatically. In addition, the volume of sediment which is transported to the estuary has also been greatly reduced, so as the siltation and extension at the river mouth, thus its impact on the upper reaches can be ignored. With the multi-year sediment regulation of Xiaolangdi Reservoir, we can take full advantage of sediment discharge by flood to further scour the riverbed of the lower reach. The current downstream reach becomes one of the most secure rivers in the world, which will inevitably affect the future prospects of governing the Yellow River basin. In order to prevent situations similar to the excessive river management in North China, which can cause the environment of the lower Yellow River to deteriorate, we should maintain the healthy life of the river, and it is necessary to adjust the scale of harnessing projects on the upper and middle reaches, as well as to construct Taohuayu Project in the lower reach for better control of floods.