Stable lowering of Tongguan bed elevation and comprehensive regulation of the lower Weihe River

Stable lowering of Tongguan elevation and comprehensive regulation of the lower Weihe River(LWR)were investigated by using field data analysis and mathematical modeling.The results can be summarized as follows:(1)Tongguan is the natural gorge of the Sanmenxia Reservoir.As the base level of erosion of LWR,the bed elevation at Tongguan station should be lowered in order to reduce siltation,to alleviate flood disasters and to improve eco-environment of LWR;(2) By means of adjusting the current operation mode of Sanmenxia reservoir,the Tongguan bed elevation could be lowered with is short-term target of 1.0m and the long-term target of 2.0m;(3) It will take about 4 to 8 years to lower Tongguan bed elevation to a relative stable status,depending on both incoming flow/sediment and reservoir operation model;(4)In the near future,for Sanmenxia reservoir,an operation mode of ungated discharging should be used in flood season with the operation water level in dry season setting at 312-318m.The upper limit of operation water level in dry season at 315m is recommended;(5) Comprehensive measures,including lowering Tongguan bed elevation,river regulation and dredging,levee heightering and stabilization as well as diverting water from other basins should be adopted for regulating LWR.