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Training

Flow Calibration in BASINS

"Water Quality Analysis Depends Entirely on Proper Flow Calibration"

How to Begin Using BASINS

    Data Extraction
  • Follow the procedure in the BASINS Users Guide in Chapter 4.2 to use BASINS "Data Extraction" Program to extract the core, DEM, and RF3 datasets.
  • The "Data Extraction" program will prompt the user for a projection. The choice of the projection is not critical, but the projection units must be in meters for the program to properly calculate landuse areas.
  • Finally, follow the procedure in the BASINS Users Guide in Chapter 4.3 to use the "Project Builder" program to create an ArcView project under the BASINS directory.
    Identify Watershed Pour Point
  • Establish the pour point at a USGS gage station with historical data for your study period.
  • The gage station (pour point) must be beyond the half-way point of the downstream reach.
  • Confirm USGS Historical Streamflow Daily Values exist for a least two years prior to your study period.
    Delineate Watersheds
  • Follow the procedure in the BASINS Users Guide in Chapter 7 and select reach file version 1 but display the RF3 and/or DEM theme in the view to guide demarcation.
  • Start delineating outside the Hydrologic Cataloging Unit boundary to just downstream of the pour point without crossing any RF3 streams. Then continue up the opposite side to outside the HUC boundary. See example.
    After Delineation
  • Compare the delineated watershed area with the USGS area value that contributes to the flow at the gage. Conversion: 1 square mile equals 2,589,998 square meters. Depending on the difference in the drainage area, redelineate or use Arcview editing tools to move the boundaries of the watershed.
  • With the Arcview measuring tool, measure the length of the main reach in the delineated watershed.
  • With the DEM activated, check the elevation at the pour point and headwaters. These measurement will be needed to compare with the measurements in NPSM.
    Run NPSM Setup
  • Follow the procedure in the BASINS Users Guide in Chapter 10
  • Enter a project name of eight characters or less with no file name extension.
  • Select the discharge year for the Permit Compliance System (PCS) data that will be incorporated into HSPF. A file containing average flow and loading values for the discharge year selected will be created for each PCS point source.
  • Select the default percent pervious, unless better data exists.
  • Enter a file name of eight characters or less with no file name extension.
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