| Runoff formation and transformation is one of the core scientific problems in hydrological research,and the influencing factors are complex.Based on the theory of hydrological time-varying gain mechanism and the model to focus the nonlinear relationship in the phenomenon of complex runoff,this paper explores the nonlinear flow mechanism of time-varying gain,and finds its connection with the main control factors,the key of theory.The results for the small river management and flash flood warning to provide an important basis for hydrological science.In this study,we study the complex rainfall-runoff nonlinear problem in semi-arid and humid areas.By carrying out outdoor artificial rainfall runoff experiment,we use the contrast control experiment variables-rain intensity and pre-soil moisture scheme to verify the traditional time-varying gain,The effects of different soil water content and rain intensity on the runoff gain were considered,and a new non-linear runoff model was established.The main research results are as follows:(1)To carry out the outdoor experiment of rainfall and runoff of natural soil,summarize the physical law of runoff under the influence of multiple factors,analyze the experimental data and clarify the core relation of the main controlling factors of nonlinear runoff:The time-varying gain curve as a whole shows a curve of the increase in runoff gain as the soil water content increases.Through the point curve analysis:different pre-soil moisture,respectively,showing a up-convex,straight,down-convex line.It is concluded that the time-varying gain relation is in agreement with the exponential relationship,which proves the correctness of the original time-varying gain theory.(2)Comparing the influence of different variables on the time-varying gain relationship,the formula of nonlinear runoff process with pre-soil moisture content and rain intensity process is put forward creatively.On the basis of the original exponential exponential formula,the effects of rain intensity factors and pre-soil water content on the yield gain factor were increased and decreased,and the soil water content was related to the runoff line.The new time-varying gain formula consists of three exponential terms:pre-soil water content,rain intensity,and time-varying soil water content.At the same time,the soil moisture content in the early stage constitutes the power item of time-varying soil water content.(3)A time-varying gain model considering rainfall intensity and soil water content is proposed,and it is applied to the study of small and medium-sized watersheds in Hubei Province,which is characterized by nonlinear relationship between rainfall-runoff,high flood peak and difficult process.The new model has improved the accuracy of the original model in the overall evaluation and the passing rate test,and can maintain the stable water balance.In the flood process evaluation,the average Nash efficiency coefficient is 91.03%,the water balance coefficient is 99.23%,the average Nash efficiency coefficient is 88.08%,and the WB water balance coefficient is 103.78%.In the simulation of flood peak,the average flood peak frequency of the four river basins decreased by 10.75%,and the average period of verification was 17.22%.(4)The correlation between soil moisture content and runoff coefficient and itsapplication in flood warning is obtained.There is a high correlation coefficient between the soil moisture content and the secondary flood runoff coefficient,which indicates that there is a certain influence on the runoff coefficient.When the rainfall reaches a certain threshold,calculate the higher soil moisture content,you need to do the corresponding flood warning work. |
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