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In order to solve the problem of sediment accumulation in the diversion canal, which adversely affects the water supply system, this paper designs a diversion and sand discharge system at the head of the canal to improve the efficiency of water use. According to the measured data of a section of the Yellow River Ningxia, a two-dimensional numerical simulation is used to construct a two-dimensional hydrodynamic model and a sediment model based on MIKE 21 for a section of the Yellow River Ningxia to simulate the water diversion at the head of the canal under two different working conditions. The results of the study show that the diversion channel changes the equilibrium of the hydrodynamic elements of the river, direct diversion canal (case 1) flow dynamics axis has oscillated 46.6m towards the concave bank, the average sand content of the channel is 0.6 kg/m³ and the maximum sand content is 0.89 kg/m³; the axis of flow dynamics in the sand reduction diversion channel (case 2) has oscillated 62.6 m towards the concave bank, the flow velocity at the head of the channel is in the range of 0.2~0.4 m/s, the average sand content of the channel is 0.2 kg/m³ and the maximum sand content is 0.6 kg/m³. Therefore, the design of the head of case 2 can improve the sediment deposition problem of the diversion canal and enhance the durability of the water intake system. [ABSTRACT FROM AUTHOR]

(Objective) Some rivers have islands. Their soil composition and geometrical shape influence water flow and sediment transport in the rivers. The purpose of this paper is to study the impact of flow rate and flowing duration on sediment erosion and hydrodynamic flow in a bended river. (Method) The study is based on two-dimensional average shallow water flow and sediment transport over riverbeds. Both water flow and sediment transport are solved using the MIKE 21. The model is applied to the section of Yellow River at Yongfeng Ferry in Ningxia province, where there are several small islands.(Result) When water flows for 3 hours at rate of 1 545 m³/s, sediment erosion reduces water velocity by 0.06~0.27 m/s and water depth by 0.02~0.32 m, compared with the results calculated without considering sediment erosion. Continuous erosion tends to stabilize water depth and flow rate. The deepest erosion depth is 0.16 m after water flows for 3 hours at rate 1 545 m³/s, and this increases to 0.24 m after the flow is increased to 6 hours at the same rate; their associated maximum deposition depth is 0.12 m and 0.23 m respectively. With the increase in flow rate and flow duration, the riverbed stabilizes, though erosion depth and deposition thickness continue to change. (Conclusion ) Sediment erosion increases the stability of hydrodynamic flow in the river, and the riverbed morphology does not change after flow rate exceeds a critical rate. These simulated results are consistent and can be used to help improve river management. [ABSTRACT FROM AUTHOR]