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US Fish & Wildlife Service FieldNotes

Water Quality Investigation of Agassiz National Wildlife Refuge, Minnesota

Region 3, September 20, 2012
cattails
cattails - Photo Credit: n/a
Agassiz NWR headquarters
Agassiz NWR headquarters - Photo Credit: n/a
Gregg Knutsen, refuge biologist, maintains a Geostationary Operational Environmental Satellites Station.
Gregg Knutsen, refuge biologist, maintains a Geostationary Operational Environmental Satellites Station. - Photo Credit: n/a
Hydrologic Technician Jaime Nielsen collects water quality samples from the refuge’s main pool during drawdown period.
Hydrologic Technician Jaime Nielsen collects water quality samples from the refuge’s main pool during drawdown period. - Photo Credit: n/a
Jaime Nielsen, hydrologic technician, and Ashley Hitt, refuge biological technician, collect water quality samples from the refuge’s main pool during drawdown period.
Jaime Nielsen, hydrologic technician, and Ashley Hitt, refuge biological technician, collect water quality samples from the refuge’s main pool during drawdown period. - Photo Credit: n/a
Linnea Thomas, environmental contaminants biologist, samples one of the refuge’s primary outflow areas.
Linnea Thomas, environmental contaminants biologist, samples one of the refuge’s primary outflow areas. - Photo Credit: n/a

In 2006, segments of rivers and ditches associated with Agassiz National Wildlife Refuge were listed as impaired for unionized ammonia, dissolved oxygen and turbidity. The mission of Agassiz NWR is to provide quality habitat for migratory birds, a mission that is compromised by water quality degradation.  This has led to poor habitat quality by: impeding the growth of native vegetation (e.g., sedges, rushes), promoting the growth of non-native vegetation (e.g., narrow-leaved and hybrid cattail), and reducing the abundance and diversity of aquatic macroinvertebrates, an important food source for wetland-dependent birds. To develop management strategies to help improve the water quality and wildlife habitat at Agassiz NWR, the Service initiated investigations through the Environmental Contaminants, Division of Biological Resources, and Science Support Partnership programs to assess the sources, pathways, loads and sediment deposition contributing to water quality impairments and habitat degradation. These studies indicate sediment accumulation and elevated concentrations of nutrients occur within Agassiz Pool—threatening the sustainability of the wetland ecosystems at Agassiz NWR (Schottler and Engstrom 2011; Nustad and Galloway 2012).

 

This investigation has guided water/habitat quality management and has assisted in the development of several proposed mitigation strategies, including sediment removal from a ditch that bisects the refuge’s main pool, construction of a bypass waterway, and an increased drawdown frequency. The Service is currently collecting supplemental water quality monitoring data and samples within Agassiz Pool (the Refuge’s largest impoundment) and at its associated inlets and outlets during the 2012 open water season.

The results of this investigation (final Service report in development) have provided critical knowledge and guidance to help reduce sedimentation and water quality problems and improve wildlife habitat at Agassiz NWR.
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By:

Elissa Buttermore
Twin Cities Ecological Services Field Office, Environmental Contaminants Program

Gregg Knutsen
Agassiz National Wildlife Refuge

Josh Eash
R3 Regional Office, Division of Biological Resources
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REFERENCES

Nustad RA, Galloway JM (2012) Assessment of Nutrient and Sediment Conditions in and near Agassiz National Wildlife Refuge, Northwest, Minnesota, 2008-2010. U. S. Geological Survey Draft Report. 55 p.

Schottler SP, Engstrom DR (2011) Sediment loading and sources to Agassiz National Wildlife Refuge. St. Croix Watershed Research Station Final Report, 22 p.

Contact Info: Elissa Buttermore, 612-725-3548 ext 205, elissa_buttermore@fws.gov