Application And Research Of Distributed Hydrological Model In Runoff-simulating Of Medium-scale Watershed Based On DEM

Hydrological model is the product of the development of hydrology at a certain phase. It enriches the hydrological system, and progresses with the development of the hydrology, and accelerates the development of the hydrology in the mass. Because of the lower level of technology, in the hydrology, the drainage area has been viewed as a whole for a long time. The terminal runoff of a watershed is ascertained with the average rainfall and parameter in the course. Though the integrate watershed hydrological model has affected the hydrology historically, it doesn't match the condition of the watershed. Not only because rainstorm distributes dimensionally at any moment, but also because soil, vegetation, topography, physiognomy, geology and hydrograph distribute unevenly in spatial dimension, and the impact on human activity varies spatial-temporally. Therefore, evidently, only a homogeneous spatial process of the runoff production and the runoff concentration is offered if the watershed with uneven underlying surface conditions is treated like a whole one with even spatial characteristic. Thus, integrate watershed hydrological model is usually unsatisfactory, but distributed hydrological model perhaps simulates actually the spatial variety of the runoff production and the runoff concentration in the course. Hence, it becomes a new aspect of hydrologic model, the hotspot in hydrological modeling field and the efficient approach to solve the problems of hydrology, ecology and environment.With the help of the hardware and software, geographic information system (GIS) is a system based on the theory of systems engineering and information science that can manage and analyze synthetically geographic data with spatial distributing property. The geographic data relate to generating and collecting runoff are mainly ground elevation and the parameters reflecting characteristic of soil, vegetation, geology, and hydrograph, especially digital elevation model (DEM) is the most useful. Not only because DEM express spatial distribution of ground elevation, but also because drainage networks and watershed boundary are generated and topographical gradient and other hypsographic parameters are extracted automatically from DEM. If DEM is combined with the spatial distribution of the parameters reflecting characteristic of soil, vegetation, geology, and hydrograph, the relation of the underlying surface parameters and ground elevation can be described. So, the distributed hydrologic model based on DEM is the primary advances in the hydrologic model in the digital age.In this paper, the methods to extract watershed properties from digital elevation data were studied, including the extraction of drainage networks, the extraction of watershed boundary and the partition of subwatershed. Making use of three sources XinAnJiang model, the distributed hydrologic model was built based on unit grid combining with subwatershed. The model was made from the following parts. The evapotranspiration, which generates the deficit of the soil storage, which is divided into three layers: upper, lower and deeper. The runoff production, which produces the runoff according to the rainfall and soil storage deficit. The runoff separation, which divides the above so determined runoff into three components: surface, subsurface and groundwater. The runoff concentration, which transfers the local runoff to the outlet of each subwatershed forming the outflow of the subwatershed. The calculation of the runoff concentration was done according to nature subwatershed applying with the runoff production of the grids, then the outflow of the whole watershed was calculated. Additionally, the precipitation data of the grids without the observation were interpolated according to the means of instance square inverse ratio. Applying the model to simulate the 28 flood of Zhitong river in Fujiang drainage networks, the results were satisfactory.In addition, the effects on extraction of watershed properties were studied from the DEM with the different bound...