THE WINVAST WATERSHED MODEL AND THE GIS INTERFACE

摘要

In this paper, the Windows version of the Virginia Stormwater (WinVAST) model is described. The model can be used to simulate Stormwater runoff and non-point source (NPS) pollution and pollutant transport. It is an event oriented model and is capable of simulating an unlimited number of subbasins. The WinVAST model is composed of four main components: 1) Watershed delineation; 2) Hydrology; 3) NPS pollutants generation and transport; and 4) pollutant routing through a structural best management practice (BMP). The watershed delineation component is used to generate the needed physical and hydrological information for a watershed. The boundaries among all subbasins are delineated and the physical characteristics of each subbasin, such as stream length, subbasin area, time of concentration, etc. are determined. The hydrology component is used to receive input hydrologic data such as precipitation, infiltration, runoff parameters, flood routing parameters, and base flow for each subbasin, and to simulate the runoff hydrograph at the outlet of each subbasin. The NPS pollutant generation and transport component is used to calculate the loading and concentration for each selected pollutant generated from each subbasin. Up to ten pollutants, which are classified into two categories, six default pollutants (NPS1) and four user-specified pollutants (NPS2) can be simulated. The last component, a BMP performance module, can simulate the fate and transport of runoff and pollutants through a selected BMP. Currently, WinVAST can simulate runoff quantity and quality in wet detention ponds and grassed swales. It is well recognized that GIS techniques can improve the data management. It is necessary therefore to develop a GIS interface for WinVAST in order to make WinVAST more user-friendly as a tool for watershed management analysis. The GIS model has the following functions: 1) Generating the watershed and stream map for the DEM map of a watershed; 2) Collecting the required data for WinVAST model from watershed, stream, soil, and landuse maps and finally the project file for WinVAST is generated.