Study On The Regional Law Of WEP?L Parameters In Distributed Watershed Hydrological Model

In the context of climate issues and global change,the description and simulation of hydrological processes have become hot research issues.Distributed hydrological model equations are based on physical mechanisms,and parameters have physical meaning,it can truly describe the hydrological cycle of the basin and provide a basis for scientifically revealing the mechanism of rainfall runoff formation.It has been widely used in many aspects such as flood control and disaster mitigation,water resources development and utilization,urban planning,reservoir scheduling,non-point source pollution assessment and human basin response.The parameters of the distributed hydrological model reflect the characteristics of the underlying surface of the basin,but when applying the model for analysis and calculation,the parameters of the model can only be determined by means of automatic optimization due to the lack of data on the underlying surface of the basin.This kind of processing makes the optimized parameter values lose the physical meaning of the original model parameters,and the effects of the model on simulation and application are also affected.In addition,the spatial variability,uncertainty and scale problems of distributed model parameters make it difficult to measure and estimate.Therefore,the construction of a national unified parameterization scheme is necessary to further enhance the universality,predictability and transferability of the model.The scientific,accurate and reasonable parameterization scheme of hydrological model has important practical significance for constructing the national hydrological cycle model,promoting the development and application of large-scale watershed water cycle model and clarifying China's water resources and carrying capacity.This paper relies on "China's water cycle flux analysis and its evolution research(national key research and development plan)".For the parameterization scheme of distributed hydrological model,the whole country is the research object.Remote sensing technology and empirical methods are used together,and the national hydrological parameters are evaluated and analyzed.The main research contents and results are as follows:(1)This paper investigates and analyzes the parameters involved in various hydrological models of various distributed hydrological models and water cycle processes,and summarize the parameters of the current typical hydrological model and its determination method.(2)Based on the application of the distributed hydrological model WEP?L model,this paper constructs a set of national initial distributed watershed model parameters based on remote sensing technology.Among them,determining the parameter partition according to the characteristics of the national underlying surface and parameters is an important part of the parametric scheme research.Based on the experience of the predecessors,this paper proposes a national parameter zoning method for the threelevel zone of nested water resources with climate zone,which provide new ideas for the distributed hydrological model parameterization scheme.(3)The leaf area index LAI of the national vegetation parameters studied in this paper ranges from-1 to 6.2 in 310 parameter zones across the country.Time: From January to August,the national LAI gradually increased,and the LAI gradually decreased from August to December.Spatially: The LAI values are higher in the southern and eastern regions,and lower in the northwest.FVC has a range of values from 0 to 0.999 in 310 parameter zones across the country.Time: The difference is obvious during the year.The best month for vegetation growth in the country is August,and the worst month for vegetation growth is March.In space,the national FVC generally shows a trend of decreasing from southeast to northwest.The Manning roughness coefficient of the national slope convergence is in the range of 0.01 to 0.3 in all parameter zones.The value of the southern region is generally higher than that of the northern region.The saturated soil moisture content ranged from 37.25% to 47.01%,and the saturated water content in the southern and northeastern regions was higher,while the saturated water content in most of the northwest was lower.The value of the national field water holding capacity ranges from 60.46% to 74.64%.The field water holding capacity in the south and northeast regions is higher,and the field water holding rate in the northwest region is lower.(4)According to the experience and experience gained in the research of this parametric scheme,with reference to the research results of the predecessors,the specific methods of remote sensing technology in the application of distributed hydrological model simulation are compiled,in order to provide more ideas and ways for the construction of distributed hydrological model parameterization scheme and distributed hydrological model.(5)The Hengduan Mountains were selected as the simulation area,and the parameterization scheme of this paper was tested by WEP?L model.According to the simulation results of Zhimenda,Benzilan,Wali and Xiaodeshi,the Nash coefficients all reached 0.7 or more,and the errors were all within 10%.This shows that the parameterization scheme of this paper is scientific and reasonable.