• Introduction
• Getting Started
• Overview of WMS
• Creating an Outlet Theme
• Editing the Stream Theme
• Making the Stream Arc Directions Consistent
• Managing Attributes
• Developing the Hydrologic Model Connectivity
• Computing Composite Curve Numbers
• Exporting and Inporting Data
• Running WMS from WMS-Hydro
• Displaying Hydrologic Modeling Results

In the past few years the availability of hydrologic modeling data layers, including digital elevations, stream reach, basin boundaries, land use, and soils, in GIS format has become common place. GIS has become established as an excellent tool for data storage and management. The Watershed Modeling System (WMS) was designed to use these and other data sets to set up hydrologic simulations for HEC-1, HEC-HMS, HSPF, TR-20, NFF, Rational Method, and other lumped parameter models.

WMS requires three primary data layers in order to build a hydrologic modeling schematic (sometimes referred to as a “tree”) from GIS data.  These three data layers include a basin boundary layer, a stream network layer, and an outlet or basin confluence layer.  In order to be able to create a hydrologic model from these three GIS vector data layers, topologic relationships between stream reaches, basin boundaries, and outlet points must be explicitly defined.  Because GIS data is often created without the purpose of hydrologic modeling in mind, and depending on the origin of the GIS data set, some editing  may need to be done to prepare the data so that a correct hydrologic model can be derived. Most of the tools available in WMS-Hydro are for the purpose of preparing these data for WMS or other similar hydrologic modeling software.

The WMS-Hydro extension for ArcView 3.x helps to prepare and transfer these GIS data from ArcView to the WMS. It is intended for use with vector data sets and does not require the Spatial Analyst extension for ArcView, but if you do have Spatial Analyst it will help to manage import and export of grid data sets for use with WMS.  Further, you will likely be able to take advantage of other extensions developed for hydrologic data developement.

The follwoing figures briefly describe the interaction between WMS and WMS-Hydro.
 

The genius behind GIS vector data are the topologic relationships that define connectivity and adjacency.  Without these, the data represents a picture or map, but it is relatively “dumb” to the computer application. Further, the definitions used by WMS for defining hydrologic models may be somewhat different than how the data were originally created.  WMS-Hydro allows you to create this connectivity so a correct topologic model can be defined.

An ArcView-WMS superfile structure has been created to allow the easiest possible transfer of data between WMS-Hydro and WMS.  Essentially the superfile is a text file identifying multiple files that can be opened from WMS or WMS-Hydro by simply reading the super file.  For the most part these files are shape files representing basin boundary, stream, and outlet themes.

The Watershed Modeling System (WMS) is designed to use GIS and other data sets to set up hydrologic simulations for HEC-1, HEC-HMS, HSPF, TR-20, NFF, Rational Method, and other lumped parameter models.

The Read Solution… command in the WMSHydro menu allows you to read the *.sol file produced by HEC-1 when run from WMS (this is the HEC-1 TAPE22 file format).  It will also read hydrograph files exported by WMS. To display a basin hydrograph view you first need to select the Select Basin Hydrograph tool   and then choose the basin whose hydrograph you wish to display.Hydrographs for outlet points may be viewed in the same manner.

WMS-Hydro works within the ArcView GIS to perform the following tasks:

• Prepare shape files of stream networks and basin boundaries for export to WMS to set up hydrologic models.



Snapping Streams Before and After.
 

• Start WMS and pass hydrologic modeling data layers directly from WMSHydro.

 
• Create a topologic representation of streams and basins where the topology is not inherently defined so that these data can be used to run hydrologic models in WMS.



Developing the Hydrologic Tree in WMS-Hydro.
 

• Compute composite curve numbers (CN) from GIS data for use in the various hydrologic models supported by WMS.

 

Computing Curve Numver in WMS-Hydro.

WMS-Hydro can compute composite curve numbers from land use, soil type, and basin boundary shape files.  Besides the three shape files used to compute CN you will need to define a mapping table that relates land use and soil ID to curve numbers for soil types A, B, C, and D. Computing CN's is done through the Compute CN… command found in the WMSHydro menu.

• Manage export and import data for use in WMS. Basin boundaries, stream networks, soil and land use layers, digital elevation, and accompanying hydrologic models can all be exported, while results from WMS, in the shape file format, can be imported.

 
• Display and review of hydrologic modeling results including hydrographs, peak flows, and time to peak. These can be displayed in combination with other base map information.



Displaying a Hydrograph in WMS-Hydro.

These materials may be used for study, research, and education, but please credit the authors and the Environmental Modeling Research Laboratory, Brigham Young University. All commercial rights reserved. Copyright 1999 Environmental Modeling Research Laboratory.