Study on Water-Amount for Sediment Transport and Critical Sediment Discharge for Keeping Balance of Scouring and Depositing in the Lower Weihe River

Weihe River is the largest tributary of the Yellow River and flows into the Yellow River at Tongguan. It is a heavily silt-carrying river with serious sediment deposition and alarming flood control problem. The characteristics of “different water and sediment sources, insufficient water, excessive sediment and extremely incoordination of the two” and the Tongguan elevation which is always staying at a high level are the root of the serious sediment deposition in the lower Weihe River. Based on the measured data and related research, the possible scenarios of the incoming sediment amount of the lower Weihe River were analyzed and a correlativity model for Water-Amount calculation of Sediment Transport in the lower Weihe river were constructed, in which both the Sediment Discharge and the allowable deposition amount was employed. To improve the calculation result，a Tongguan elevation correction factor was introduced into the correlativity model. With the improved model, the Water-Amount for Sediment Transport to maintain annual deposition amount of 0.1×10⁸t in the lower Weihe River will be 37.4×10⁸m³ and 42.8×10⁸m³ respectively for different possible scenarios at 1.9×10⁸t and 2.4×10⁸t of incoming sediment amount in flood season. And considering the function of DongZhuangReservior after the storage period，the Water-Amount for Sediment Transport will be 35×108m³ and 41×108m³ respectively. Through the multi-mode set prediction, the critical sediment runoff of the scouring and depositing balance in the lower Weihe River is around 0.37-0.39×10⁸t.