Watershed Modeling System(WMS)是非常有名的流域模擬分析軟體，在全程支持流域（分水嶺）的水文地理學，水力學的圖形化建模。是美國地質調查局和環保局批准的環境模擬軟體

WMS The Watershed Modeling System is a comprehensive hydrologic modeling environment. WMS provides tools for all phases of watershed modeling including automated watershed and sub-basin delineation, geometric parameter computation, hydrologic parameter computation (CN, time of concentration, rainfall depth, etc.) and result visualization. Used at hundreds of government agencies and private firms around the world, WMS is the most powerful tool for analysis and visualization of watersheds.

WMS provides complete support of the industry-standard U.S. Army Corps of Engineers HEC-1 and HEC-HMS, U.S. Soil Conservation Service TR-20 and TR-55, and Rational Method Equation hydrologic routing programs. Also supported the National Flood Frequency (NFF) model, which was developed by the USGS in cooperation with the Federal Highway Administration (FHWA) and the Federal Emergency Management Agency (FEMA). In addition, support for the EPA/USGS hydrologic water quality HSPF model is also provided.

The program's modular design enables the user to select modules in custom combinations, allowing the user to choose only those hydrologic modeling capabilities that are required. Additional WMS modules can be purchased and added at any time. The software will dynamically link to these subsequent modules at run time—automatically adding additional modeling capability to the software.

Graphical User interface 
Thanks to the graphical tools of WMS, with standard MS Windows functionality, building models and viewing results is very easy and intuitive. All modeling parameters are entered through interactive graphics and easy-to-use dialog boxes. Though the software reads and writes native model input/output files, there is no need to worry about formatting text files to get the models to run nor will you need to search through text output files to find the results from the model run.

Thanks to simple CAD/GIS style tools and functionality, you will find that manipulating digital terrain data and GIS data to delineate watersheds and compute model input parameters is very smooth. Further, presentation of results of your work will be impressive and easy to understand.

Graphics and Visualization 
WMS is a powerful graphical tool for model creation and visualization of results. Models can be built using digital maps and elevation models for reference and source data. During the model building process, the graphical representation of the model allows quick review and presentation of your work. Fully 3D views, with contouring and shading, of your model allow anyone to see and understand the domain and parameters of your analysis.
Watershed display options include elevation contouring, basin-boundary outline or color fill, streams, time of concentration flow path plotting, base map (orthophotos, USGS Quad maps, etc.) rendering, and many others. Watershed data such as areas, slopes, flow distances, basin centroids, etc. can be displayed as well.  Model results such as hydrographs can be plotted with a variety of plotting options. Further, floodplain results can be reported as flood depth maps, flood extent maps, and flood impact maps - all scalled and reported in real-world coordinates.

  WMS Modules 
The WMS interface is separated into several modules; these modules contain tools that allow manipulation and model creation from different data types. The modules of WMS are: 

Map Module 
DEM Module 
TIN Module 
Hydrologic Modeling Module 
Scatter Point Module 
2D Grid Module