Science of Watershed Health


Downscaling health scores

The Watershed Health Assessment Framework was developed using Minnesota's 81 major (HUC 8) watersheds as the scale for calculating health scores. 

Perennial Cover by Watershed

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Major watersheds organize the landscape into areas that are connected by common hydrologic systems; with land area that slopes toward a common water body such as a major river or lake.  This division creates administrative watersheds ranging from 40,000 to 250,000 acres in size.  Major watershed boundaries are used by other state agencies such as the Pollution Control Agency (PCA) and the Board of Water and Soil Resources (BWSR) as well as local governments and non-profit agencies. 

An example of a major watershed health index is the Perennial Cover Index.  The amount of perennial cover (permanent vegetation) that remains in each major watershed was consistently calculated across the state.  At this scale, the results show trends in the statewide pattern, as well as trends within Minnesota's major river basins. 


Downscaling Health Scores

Some health index relationships use data that can be quantified to a finer spatial scale.  The scale selected to "downscale" these indices is the DNR Catchment.  There are more than  10,000 catchments within Minnesota and by calculating health scores to this scale, patterns in health emerge that will help manage systems within the boundaries of the major watersheds.  The scores also reveal patterns that cross major watershed boundaries that can help inform coordinated management approaches. 

The WHAF "Explore" interactive map displays the health scores that are available at the catchment scale.  To properly view these scores, the user should use the upstream tool to identify (select) all catchments upstream of the selected catchment of interest.  These identified (selected) upstream DNR Catchments represent the total contributing area, which is the true, or total watershed for the outlet of the DNR Catchment originally selected when executing the tool.

Perennial Cover by Catchment

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St. Cloud Catchments

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DNR Catchment Definition:

The smallest delineated and digitized drainage area mapped by the Minnesota DNR Watershed Delineation Project that contains all land area(s), as well as noncontributing inclusions and water features, upstream from, or between Hydrologic Points of Interest (HPOI)defining other DNR Catchments.

Individual DNR Catchments are not true Watersheds unless they represent a DNR Headwaters Catchment. Therefore, DNR Catchments used for hydrologic analysis should include the upstream catchments that are contributing flow.  DNR Catchments should not be used independently for hydrologic analysis because the hydrology of the landscape would not be properly represented by the results.