| China's agricultural water environment is very uneven distribution of time and space,rainfall and runoff is an important factor in the formation of agricultural water environment,a greater impact on grain yield and quality,potentially affecting the watershed,wetlands and other ecosystems.In addition,rainfall is the main reason for the formation of runoff,surface runoff is extremely sensitive to changes in rainfall,a rapid increase in a short period of time easily lead to floods,a huge impact on agriculture.The rainfall runoff model is a conceptual hydrological model that simulates the runoff process of surface runoff from rainfall.It is a combination of the physical structure and semi-empirical formula of hydrological cycle.The model uses historical hydrological data to optimize the parameters of the basin to approximate the runoff process.It has been widely used in flood control and control,water resources development and utilization,water environment and ecosystem protection and other fields.In order to study the relationship between rainfall and runoff in the basin,improve the simulation accuracy of the rainfall runoff model,and find a suitable method for the model,the NAM rainfall runoff model was adopted and the sensitivity of the model parameters was analyzed.The runoff of the Upper Sangamon basin in the Illinois and the Wuyuer River basin in the northeastern part of China was simulated by simplex method and genetic algorithm.The following works were done:(1)The parameters and structure of NAM rainfall runoff model were introduced,the specific rate method was determined and the evaluation criteria of the model was given.The basic principles of the research area,data source and data processing method were explained.(2)The 9 main parameters in NAM model were selected and the runoff data were from Fisher observation station and meteorological stations of Upper Sangamon River,Illinois.They were investigated based on analyzing the variation of runoff under the condition of parametric changing.Then the sensitivity of the 9 important main parameters to the model's simulation results were analyzed by the perturbation method.The sensitivity level of each parameter was obtained,which provided the basis for the parameters of the next step.(3)The strategy of simplex method and the genetic algorithmwere introduced based on the sensitivity analysis of the model parameters,the maximum water content of the Lower Zone Storage Lmax,the maximum water content of the Surface Storage Umax,the surface runoff coefficient CQOF and the critical value of the groundwater runoff TG are taken as the main parameters.The intermediate parameters of the NAM model of the Upper Sangamon basin and the Wuyuer River Basin were obtained by two kinds of method respectively.The daily runoff process of different methods was obtained,and the correctness and reliability of the two methods were verified.(4)In order to consider the applicability of the two methods in different conditions,the daily runoff results were compared,and the results show that the NAM model can be selected according to the initial conditions of the catchment,which lays the foundation for the subsequent improvement of the model simulation accuracy. |
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