1. Determine what data you need and where it can be located.
2. Obtain the necessary data from one of several possible sources.
3. Format the data, if necessary.
4. Import the data into WMS.
5. Use the data for watershed delineation and hydrologic modeling.

NOTE:  Different types of data coming from different sources may be in different coordinate systems. When using multiple data layers together, they all must be in the same coordinate system.  For example, land use and soil type data are often in geographic coordinates (latitude, longitude).  Elevation data such as a DEM might be in UTM NAD27 in meters.  To overlay the soil type and land use data on top of the DEM, all data must be converted to a common coordinate system.  It does not matter which coordinate system is used, but if the majority of your data are in a UTM NAD27 coordinate system, it may be easiest to convert all the rest to this same coordinate system.  Sometimes it is not obvious what coordinate system your data are in.  In this case, you must find the metadata.  The metadata (data about the data), which should tell you what coordinate system the data are in, is typically available on the same website or in text documents attached to the data itself.  If you cannot find information about the data's coordinate system, import the data into WMS or a GIS to see if it is in geographic coordinates (latitude/longitude).  Stand alone programs such as Corp Con will convert a single point (or a batch file of multiple points) from one coordinate system into another.  GIS systems such as ArcView can easily convert shapefiles from one coordinate system to another through the use of the Projector extension.  WMS v6.1 is also capable of converting many types of spatial data into different coordiinate systems.  In this case study, the 7.5-minute DEM used is in a UTM NAD27 coordinate system -- therefore, the easiest thing to do is to convert other data types (such as land use) to UTM NAD27. Click here for help on converting spatial data into a different coordinate system with ArcView GIS, or click here to learn how to do it in WMS v6.1. Click here for a general overview on coordinate systems, projections, and datums.

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Obtain DEM Data

1. Go to the GSDA website.  Click on the DEM link.  Here you can obtain, learn about, and read tips related to DEM data.  Choose the OBTAIN DEM DATA button.
2. Determine which DEM you will need.  To obtain DEM data it is helpful to know in which quadrangle (and sometimes which county) the outlet point is located.  Although not always necessary, the USGS GNIS (Geographic Names Information System) can be used to do this.  Click here to learn how to use the USGS GNIS.  Another helpful tool for determining which USGS quadrangle a feature is located in is the USGS MapFinder.  Click here to learn how to use the USGS MapFinder.  After trial and error, it is determined that Lost Creek is located in the "Mirror Lake" USGS 7.5-minute quadrangle in Duchesne county.
3. Obtain the Mirror Lake 7.5-minute (1:24,000 scale) DEM from the USGS. Click here for a similar example of doing this.  Click here for help on uncompressing data files.
4. Format the DEM, if necessary.  This may mean converting the DEM to the coordinate system you will be working with.  For help on doing this, click here.
5. Import the Mirror Lake DEM into WMS. Click here for an example.
6. Delineate the watershed using TOPAZ.  The goal is to alter the flow accumulation threshold until it matches fairly well to the streams actually in the watershed.  Hint:  A flow accumulation threshold of about 600 gets it about right.  See the WMS tutorials for help on delineating watersheds with a DEM.   USGS 7.5" DEMs are in UTM NAD27 (meters).  Since the watershed is completely contained within the Mirror Lake DEM so importing another DEM is not necessary.  Since the watershed is relatively small (2.2 square miles), we could simply use a DEM without dividing the basin into sub-basins.  To take advantage of the features a TIN offers, proceed to delineate the watershed with a TIN using the DEM as the background elevation source. See the WMS tutorials to learn how to delineate a watershed as a TIN.  Recommended distribution of vertices for a small watershed such as this is about 100 meters or less for this size of drainage basin.

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Obtain Image Data

1. Go to the GSDA website.  Click on the IMAGES link.  Here you can obtain, learn about, and read tips related to image data.  Since a topographic map would be nice, choose the OBTAIN DRG IMAGE DATA link.
2. Obtain the DRG image from GIS Data Depot.  For help doing this, click here.  Remember that it was previously determined that our watershed is located in the Mirror Lake quadrangle in Duchesne county.  Click here for help on decompressing data files.
3. Format the DEM, if necessary.  This may mean converting the DEM to the coordinate system you will be working with.  For help on doing this, click here.
4. Import the DRG into WMS.  For more help, click here.  Hint:  These DRGs are in a UTM NAD27 coordinate system.

Watershed boundaries with DRG in background.

Oblique view of the watershed with the DRG draped
over it.  The Z-axis is exaggerated by a factor of 2.

Another type of data which may not be as useful in an "engineering sense" but would serve other purposes is a DOQ (Digital Orthophoto Quarterquadrangle).

1. Go to the GSDA website.  Click on the IMAGES link.  Here you can obtain, learn about, and read tips related to image data.  Click on the OBTAIN DOQ IMAGE DATA link.  DOQ images are sometimes a bit harder to find for all areas of the US.  The DOQ for this watershed below came from the Public Sites option at the GSDA website.  Read and explore the "Obtain DOQ" webpage more to learn about obtaining DOQs for other areas.

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Obtain Soil Type Data

1. Go to the GSDA website.  Click on the SOIL TYPE link.  Here you can obtain, learn about, and read tips related to soil type data.  Click on the OBTAIN SOIL TYPE DATA button.
2. Obtain soil type data from the EPA. Click here for an example of doing this.  Hint:  From trial and error, we determine that our watershed is located in the EPA Duchesne Watershed.  Click here for help on decompressing data files.
3. Format the soil type data so that it can be used in WMS.  (1) Since EPA soil type data are in latitude/longitude, it must be converted to the same coordinate system the other data are in (i.e., UTM NAD27).   (2) You must also join the hydrologic soil group attribute from the 'statsgoc.dbf' table file to the 'statsgo.shp' shapefile.  (3) It is often easier to clip out the soil type data with your exported watershed from WMS.  Click here for more help on doing these three things.
4. Import the soil type data into WMS. Click here for help.

EPA soil type data for the EPA Duchesne watershed.
 

Soil type boundaries when clipped with the watershed boundaries.

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Obtain Land Use Data

1. Go to the GSDA website.  Click on the LAND USE link.  Here you can obtain, learn about, and read tips related to land use data.  Click on the OBTAIN LAND USE DATA button.
2. Obtain land use data from the EPA. Click here for an example on how to obtain land use data from the EPA. Click here for help on decompressing data files.  Hint: Although there are three shapefiles in the "landuse" folder.  By trial and error it is determined that 'l_saltut.shp' is the right one.
3. Format the land use data for use in WMS by converting the data to the common coordinate system.  You may also want to clip out the land use data with your exported watershed from WMS. Click here for help on doing these two things.
4. Import the land use data into WMS.  Click here for help.

EPA land use data.
 

Land use boundaries when clipped with the watershed boundaries.
 
 

The Lost Creek watershed with both the soil type and land use polygons.

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Obtain Precipitation Data

1. Go to the GSDA website.  Click on the PRECIPITATION link.  Here you can obtain, learn about, and read tips related to precipitation data.  Click on the OBTAIN PRECIPITATION DATA button.
2. Obtain precipitation data for the 24-hr 50-year storm event from the Regional Climate Center (RCC) NOAA Atlas 2. Click here for an example of doing this.  Hint:  The 24-hr 50-year storm event should produce about 3.2 inches of rainfall (see figure below).

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Obtain Hydrographic Data

1. Go to the GSDA website.  Click on the HYDROGRAPHY link.  Here you can obtain, learn about, and read tips related to hydrographic data.  Click on the OBTAIN HYDROGRAPHIC DATA link.
2. Obtain the "Line Features, Streams" shapefiles  from ESRI Census TIGER 1995. Hint:  Although the Lost Creek watershed is close to the border of Duchesne, Wasatch, and Summit counties, it is determined through trial and error that Summit county is the correct one.  Click here for an example on obtaining hydrographic data from ESRI Census TIGER 1995.
3. Format the hydrography shapefile for use in WMS by converting it to the common coordinate system.  You may also want to clip the hydrographic data shapefile with the exported watershed boundaries from WMS.  Click here for help on these two things.
4. Import the hydrographic shapefile into WMS to see how known streams match up with your watershed.  Click here for help on doing this.

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Run a HEC-1 Hydrologic Model

1. Use the SCS CN loss method.  Compute a SCS/NRCS composite curve number for the watershed.  The curve number will vary depending on the CN table used.  If you use the tables found in the WMS tutorial folder, you should get a composite curve number (CCN) of about 85.4.  Click here for more help on creating a land use table.  See the WMS tutorials for help on computing a CCN once a land use table has been imported.
2. Input the precipitation data obtained from the RCC.  Input the 3.2 inches as a basin average since we do not have gage data.
3. Use SCS Dimensionless for the unit hydroraph method.  Compute the lag time with the custom method using the basin data equations. Refer to the WMS turorials for help.  You should get a lag time of about 0.59 hrs and a time of concentration of 0.98 hrs.
4. Check, and then run the HEC-1 model, referring to the WMS tutorials for help.
5. Display the results.  They should resemble the numbers and figure below.

• Peak flowrate:  Q_p = 1,238 cfs.
• Time to peak:  t_p = 12.5 hrs.
• Runoff volume:  R = 8,881,788 ft³(204 acre-ft or about 1.78 inches of runoff).  Since R = CP, the runoff coefficient for this watershed is about 0.56.