Lingzhuangzi waterworks in water processing adopts drug concentration of water body method to monitor and to determine the reasonable dosage.The method first dosing and monitoring of drug concentrations,after initial dosage judging by experience,which wastes manpower and cannot guarantee the result accurately.The determined dosage must first clear streamflow,reservoir a submerged inlet for the nonstandard rectangle thinwall weir,therefore,unable to use the existing flow formula calculation flow of traffic.At the entrance of the weir,there are both free outflow and submerged outflow. To obtain a more accurate flow rate,the physical model test method was adopted,and the model with a geometric scale of 1∶5 was made according to the gravity similarity criterion for experimental research.The experiment is carried out to analyze the flow change process of the weir.The appropriate position of the weir before and after the weir at the inlet of the water plant reservoir is set up,and the corresponding physical model is made. The actual flow capacity of a rectangular thinwalled weir is reduced due to the influence of the weir plate groove.The empirical value of the flow coefficient was Cd1=0.056 9h/p+0.597,and the measured value was Cd2=0.828h/p+ 0.543 8,respectively.The free flow formula was calculated by Cd2without considering the influence of surface tension.Submerged discharge conditions can be used to scale according to different valve opening and close the valve opening as a group,the outlet valve opening corresponding to the actual engineering of the middle and lower reaches of reservoir level can be carried out on the downstream water level "sectional processing",namely the designated several water level range,as a set of each water level range,according to the flood discharge formula in the calculation,flow coefficient,different groups of corresponding parameters a and bvalues. Through the model test,the flow variation law of free flow and submerged flow of the weir in Lingzhuangzi waterworks are studied,the test results show that it is feasible to preliminarily calculate the overflow by the water level in front of the weir and behind the weir,and the calculation ideas of the flow are given respectively. Compared with the standard rectangular thinwalled weir,the weir plate groove of the water conservation weir in the waterworks reduces the free flow capacity,and the measured flow coefficient is Cd2=0.828 h/p+0.543 8.The free outflow can be calculated directly by formula using flow coefficient Cd2.When the outlet valve has a certain opening,the submerged water depth increases with the increase of the incoming flow;when the flow rate is constant,the submerged depth decreases with the increase of the opening of the outlet valve;and when the downstream valve opening is certain,the submergence coefficient Cf has a mathematical relationship with h/p,and the submergence coefficient Cf of several similar valve openings applies to the same value of a and b.Outlet valve opening corresponding to the actual engineering of the middle and lower reaches of reservoir level,according to different groups,the downstream water level giving to the flood discharge formula,refer to historical traffic data,the relationship between the primary parameter values constantly in the process of practical application to modify parameters,the accurate calculation formula can be obtained,and then the automatic control of dosage can be realized.