Watershed Achievements Report

Cedar River Basin Watershed Achievements Report 2015
Cedar River Watershed
Cedar River Alternative Ditch Designs
Sediment and nutrient loading to the hypoxic zone of
the Gulf of Mexico is well documented, and significant
portions of the loading have been attributed to the
upper Mississippi River basin resulting from extensive
agricultural production acreage. Small streams and
ditches provide the best opportunity to mitigate the
high levels of nutrients from subsurface tile drainage.
Drainage ditches are limited in their removal potential
because they are relatively narrow and are periodically
dug out for maintenance. Maintenance of drainage
channels is expensive for landowners. Alternative designs
to these ditches have the potential to ameliorate the
environmental impact of drainage and to reduce the cost
of maintaining them.
Goals
The project focused on evaluating alternative designs
for agricultural drainage ditches that are of statewide
interest. The work did improve the Mullenbach drainage
ditch located in the Cedar River Basin.
Five years of water quality and quantity data were
analyzed, which included more than 100,000 continuous
nitrate, flow, pH, conductivity, temperature and
precipitation readings as well as more than 1,000 grab
samples of other types of water quality variables. In
addition, data were collected to evaluate the physical
stability of the ditch and changes in the biological
characteristics. Tools were developed to assess the
feasibility of two-stage ditches using economics and
physical conditions of the sites.
Results that count
Two-stage ditch was a successful alternative design. It
improved the habitat for fish and, hence, improving their
Fish index of biological integrity (IBI) scores. The number
of pools and riffles increased from 5 to 65 and from 5
to 68, respectively, from pre-construction to 2013. The
design is stable with relatively moderate increase of 11%
in bank width over the project duration. Denitrification
rates were estimated to between 10% and 30%. More
research is needed on the alternative design of rock inlet,
seepage trenches and bench treatment systems.
Financial information
Funding type: Section 319
Grant amount: $286,128
Matching funds: $87,000
Final in-kind: $148,904
Contact information
University of Minnesota
Bruce Wilson, Professor
1390 Eckles Avenue
St. Paul, MN 55108
612-625-6770
wilson@umn.edu
MPCA Project Manager: Charles Regan
Two stage Mullenbach drainage ditch in Mower County, Minnesota
Minnesota Pollution Control Agency www.pca.state.mn.us 48