The USGS StreamStats command allows the user to click on a stream location in the Map View, and the software will delineate the watershed basin boundary, compute the basin characteristics, and provide estimates for flow based upon site-specific USGS regression equations. The software will generate GIS shapefiles containing the determined watershed boundary and basin characteristics, stream flow path, as well as a PDF results report for the selected site. This section describes how to use this command.
From the Watershed ribbon menu, click the USGS StreamStats command.
The USGS StreamStats dialog box will be displayed.
The following sections describe USGS StreamStats command and how to interact with the above dialog box.
This section is used to define general information on the watershed being computed.
Click the [Pick] button to select a watershed outlet point (or spill point) from the Map View. This selected point should be on a known stream, river or other waterway. The software will use this point to compute the contributing watershed drainage basin and the discharge at the selected point.
When selecting this watershed outlet point, the dialog box will temporarily disappear and the user will be prompted to select the outlet point. After selecting the point, the user will be returned to the dialog box and the software will also display the picked point’s latitude-longitude and the corresponding address for the selected point.
Drainage Basin Boundary
This section is used to define where the computed results are to be saved and whether the watershed boundary should be added to the Map View.
Click the […] button for the Shapefile path entry to specify the directory location to save the computed USGS StreamStats results.
The Computational Process
Click the [Compute] button and the software will the call the USGS StreamStats webserver with the selected watershed outlet point. The USGS StreamStats webserver will then place your request into a queue (if there are any other user requests in front of it).
Once your request begins processing, StreamStats first determines the drainage basin associated with the picked point. It performs a watershed delineation using the National Elevation Data (NED). It then determines the longest flow path within the computed watershed, along with the stream slope, watershed average slope and other hydrologic parameters. From the computed watershed centroid, it determines which state the watershed is in and which regional runoff regression equation should be used to estimate the flow-duration statistics for the selected point.
The USGS is continually improving this computation, adding regions that were not previously covered as well as updating the runoff regression equations for computing peak flows based upon additional stream gages and revised flow statistics. These changes and improvements are automatically incorporated into the USGS StreamStats webserver.
Once this information has been determined, StreamStats packages together a ZIP file containing the results and sends that ZIP file back to our software. Our software then unpacks the ZIP file and post-processes the provided results and displays them in the dialog box, Map Data Layers panel, and on the Map View.
The following dialog box sections display the computed results:
- Drainage area (the General Information section)
- Peak Flow Basin Characteristics
- Peak Flow Streamflow Statistics
Click the [Report] button to display the USGS StreamStats PDF report showing the streamflow statistics and peak flows. This PDF report is also appended to the Map Data Layers panel data listing for easy retrieval.
The Map Data Layers panel also lists the downloaded shapefile layers that were generated by USGS StreamStats. These layers are GIS attributed and contain the computed results.