The stepped low pressurized water diversion system is a new type of gravity water supply system, which is simple in structure and water conservation weir is the pivotal structure. In this paper numerical models for unsteady flow result from inspection are established to simulate the overfall and well flow patterns respectively. The result of numerical simulation shows the surge chamber or open channel set between the bulkhead gate and downstream pipeline can alleviate hydraulic oscillation resulted from inspection. Then the alleviation effect is compared between the two alleviation sets.The research also find out that the improper area of alleviation set can enlarge hydraulic oscillation of the water level of downstream conservation weir well. At last,based on hydraulic control and analysis, the principle of optimization to water conservation weir well and alleviation sets is proposed. All the researches above can offer technical grounds for the design, meanwhile the optimization principle has broad application value.
