Roads
are available for review. There are three factors which gave impetus to
this modeling effort: Miller Creek's status as a Brook Trout stream with
natural reproduction, the significant amount of commercial development
occurring in the upper part of the watershed, and the impending regulation
of stormwater in cities with populations between 50,000 and 100,000 by
the U.S. Environmental Protection Agency.
SWMM, the EPA-developed Storm
Water Management Model (see here
for distribution information) was chosen for several reasons. SWMM was
developed by the EPA from 1969 to 1971, and has been modified and upgraded
over the years by universities, private consultants, the US EPA, and others (James
et al. 1998, Huber and Heaney 1976, Jewell et al. 1976, Donigian and Huber
1991). There is a wide body of literature documenting its use and an
internet list-serv (http://www.chi.on.ca/swmmusers.html) where new and
veteran users post questions and answers, tips, and problems associated
with using SWMM. Also, the PCSWMM front-end developed by Computational
Hydraulics International is a relatively inexpensive program which
simplifies some of the procedures necessary to run SWMM. In short, SWMM
is widely used, widely documented, supported since its development, and
has an inexpensive program available to reduce the required learning-time.
Specifically, we used PCSWMM 98, which uses the SWMM 4.4 engine.
We used a two-year hourly discharge dataset
for three sites along the Miller Creek mainstream to calibrate and validate
the flow portion of the model. This data was collected by the Minnesota
DNR in 1997 and 1998. The locations of these sites are on each watershed
map, and are listed as the "DNR Sites". Pollutant calibration data was
obtained from the Minnesota Pollution Control Agency (MPCA) for 4 subcatchments
within the watershed. The data provided was single-event storm loads for
each pollutant, covering 3 to 5 storm events for each site. Concentrations
were not available. These sites are labeled as "MPCA Sites" on the maps.
All data sites are included in each image for reference.
The expected outcome of this effort was a
water quantity model calibrated and validated for three points along Miller
Creek and a quality model with enough calibration to allow for scenario
and paired-basin analyses. Confidence in the quantity portion of the model
is much higher than the quality portion due to the amount of available
data for calibration and validation. There is a relatively high uncertainty
associated with the quality model. Thus, the actual pollutant concentrations
and loads are suspect, however the relative changes associated with paired
basin analysis or applied scenarios such as increased development or channelized
waterways can be viewed with greater confidence.
A total of 9
scenarios were analyzed for flow and each of the 4 pollutants (Nitrate,
Total Dissolved Solids, Total Phosphorus, and Total Suspended Solids) and
reported as % change from the original model, as it was calibrated for
the current set of conditions. Several scenarios have multiple parts, resulting
in 14 different sets of watershed conditions modeled. Detailed descriptions
of each set of conditions are included.
Results
Results have been sorted in two ways. Either you can view results grouped
by a specific constituent, for all scenarios, or view results grouped by
scenario. The constituent grouping should allow easier determination of
how the various scenarios affected any one of the constituents, while the
scenario grouping should allow easier determination of the overall effect
of the scenario on all parameters analyzed.
The Miller Creek project was jointly funded by the Minnesota Legislative Commision on
Minnesota Resources and the LSDS project.
For Questions or Comments on Miller Creek, contact:
Carl Richards
Minnesota Sea Grant
2305 E 5th St
Duluth, MN 55812
Phone: (218) 726-8710
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