Flow Calibration in BASINS
Compare Modeled and Observed Flow
Time Series Output:
- Execute NPSM and graph the results for stream flow (RO variable).
- Import USGS
daily historical streamflow measurements for the designated gage at
USGS Historical Streamflow Site
(output format: tab-delimited text & MM/DD/YYYY).
- Initially compare full year in question under "Data Comparison" button
of Postprocessor. The goal is to have annual simulated and observed
flow values within 10% of each other, as well as coinciding peaks (see
- To rapidly zoom into a specific time period in the post processor,
hold down Shift key, click the mouse on the new start point,
drag the pointer to the end-point, and release the mouse before the
- To rapidly highlight a specific value range in the post processor,
use the Ctrl key and the mouse to highlight the range of interest.
Release the mouse before the Ctrl key to activate the change.
Identify Potential Sources of Discrepancy:
- Look for consistent annual, seasonal or storm event differences between
simulated and observed flows.
- Think about the land uses that dominate the watershed and consider
how those might effect seasonal patterns.
- Frozen ground and SNOW effects.
- Identify potential gaps in precipitation data using either the Postprocessor’s
Weather Station or the WDM Utility. Avoid changing precipitation data
unless your sure its incomplete or incorrect.
- Look for unaccounted flow diversions.
Modify Data Editor
Introduction | Previous Page |
- Changes are made to the parameters within Data Editor based on known
watershed characteristics, or from discrepancy patterns between simulated
(NPSM) and observed (USGS) flow values. Consider using values from the
HSPF Parameter Database that might more closely resemble the watershed
- Look for consistent annual, seasonal, storm, and high-low flow discrepancies.
- Precipitation can only leave the watershed as runoff, underflow,
evapotranspiration, or diversions.
- Remember to assign each parameter change to all land uses! Also make
sure new values are within the range of acceptable minimum and maximum
- Most importantly, save often. There are two crucial areas to save.
- It is important to regularly save the project itself in case the
version being worked on becomes corrupted.
- It is also helpful to save each output file generated after every
parameter modification. This needs to be done manually in Windows
Explorer. Under BASINS’ Modelout, go into the folder that contains
your project and then into the Reaches folder. Inside will be a file
that begins with “R0_” (see figure). You
must keep the three number extension, but change the eight digits
on the left to reflect your modifications. Each output run will add
a new file exactly the same as the original (usually they just overwrite
each other), and those can be labeled similarly. To bring any of these
output files into the Postprocessor, use the NPSM Data button.