How many meters does the flood level of Sanmenxia Reservoir rise due to siltation?

The river bed elevation is different in different areas.

It is reported that in the second year after the Sanmenxia Reservoir was impounded, that is, at the end of19610, the sediment washed down from the upstream reached 3.6 billion tons (in the words of Zhang Guanjun, director of Sanmenxia Flood Control Office), and the sediment was deposited in the Sanmenxia-Tongguan River, making it impossible for the Weihe River to flow out. When the water level of the Weihe River basin reached 332.5 meters, the water level and groundwater level rose in an all-round way. The flood flooded 300,000 mu, 5,000 people were trapped, and the upper reaches of the river were silted up. Since March 1962, Sanmenxia Reservoir has been operated with low water level for flood detention and sediment discharge. However, due to the large sedimentation at the bottom of Tongguan River, backwater backflow is more frequent and serious. 1964, 1966, 1967 have backflow. Among them, 1967, the 8.8km estuary section was completely silted, the water level rose by 2.5m, and 300,000 mu of cultivated land was flooded. Even in 197 1 year and 1977, after Sanmenxia Reservoir added flood discharge and sediment discharge measures twice, serious siltation occurred. In recent years, due to the large amount of water storage in the middle and upper reaches of the Yellow River and Weihe River, the inflow has decreased, the river channel has shrunk, and the Tongguan river bed has been continuously silted. Now it has reached an altitude of 328 meters, and the siltation of Weihe River continues to develop, and the end point of siltation is more than 200 kilometers away from the estuary. In order to resist the rise of flood level caused by serious siltation of riverbed, tributaries such as Weihe River, Beiluo River and Nanshan had to build dikes and raise them twice. However, the standard is low and the flood control is difficult. The waterlogging outside the dike cannot be discharged into the Weihe River by itself, which aggravates the flood disaster and threatens the safety, production and life of 6,543,800 people outside the dike and 6,543,800 people in the beach area.