Application Of Improved Runoff Curve Model In Calculation Of Surface Runoff In Small Watersheds In Beijing

There are five major rivers in Beijing: the Chaobai River,the North Canal,the western Yongding River and the Juma River.These rivers converge into many small watersheds,and there is not much rainfall in the basin,and water resources are scarce.Therefore,the rational use of water resources is imperative.Soil Conservation Service Curve Number(SCS model)is a method used to study the relationship between rainfall and runoff.The Soil Conservation Service Curve Number(SCS model)requires few parameters and is easy to obtain data.It is a good model for calculating rainfall runoff in small watershed,so it has been widely applied to all parts of the world.The SCS model considering the basin rainfall runoff curve,land use,vegetation coverage,such factors as the antecedent soil moisture,but according to the standard curve of SCS runoff model to calculate runoff there will be a larger difference,so for a certain river basin are required for application model was improved,improve the model accuracy correction model parameters.This article takes the control watershed of dahongmen station and yangfang gate station in Beijing area as research objects,USES the field rainfall runoff data,applies the standard SCS runoff curve model and the improved SCS runoff curve model to calculate and verify the runoff.(1)The CN number of runoff curves under different land use patterns is constant.The predictive value of surface runoff decreases with the increase of the initial loss coefficient,except the unused land.When the number of runoff curve CN is constant,the sensitivity of different land use patterns is different under certain rainfall conditions.Under certain rainfall conditions,the number of runoff curve CN decreases,and the surface runoff is more sensitive to the initial loss coefficient.When the CN value is constant,the initial loss coefficient lambda relative sensitivity decreases with the increase of rainfall P.(2)The standard SCS runoff curve model does not consider the soil moisture content M at the early stage,and the rainfall index API at the early stage only represents the soil moisture degree at the early stage,but cannot effectively represent M.The improved SCS runoff curve model can represent the soil moisture content through M=aAPI.Improved SCS runoff curve model when choosing parameter lambda lambdatake 0.02,using the algorithm of test curve of SCS runoff model and improvement of the standard curve models of relative error of the SCS runoff RE all within a reasonable range,but the improvement of the SCS runoff correlation coefficient R curve model is bigger,and the improvement of the SCS runoff model fitting curve model efficiency coefficient is close to 1,E simulation effect is better.(3)The accuracy of the improved SCS runoff curve model was significantly improved when the rainfall intensity was considered in the control basin of yangfang gate station.According to the 35 daily precipitation data of yangfangzha station from2000 to 2018,the 30 minutes with strong rainfall will have a great impact on surface runoff and erosion,and the ratio of the maximum rainfall of 30 minutes to the secondary rainfall reflects the degree of rainfall concentration.In guarantee under the condition of model fitting of high efficiency,the prediction correlation degree as high as possible,choose the early damage of coefficient of lambda is 0.22 as improved runoff curve model parameters.