THREE DECADES OF WATER QUALITY CHANGE (1976-2005) IN THE MISSISSIPPI NATIONAL 
RIVER AND RECREATION AREA

Brenda Moraska Lafrancois1, Suzanne Magdalene2, D. Kent. Johnson3
 
1National Park Service, Marine on St. Croix, MN 55047, 2St. Croix Watershed 
Research Station, Marine on St. Croix, MN 55047, 3Metropolitan Council 
Environmental Services, St. Paul, MN 55101

The Mississippi National River and Recreational Area (MNRRA) spans a 116 km 
stretch of the Mississippi River in the Twin Cities Metropolitan Area.  
Although many agencies monitor Mississippi River water quality, none has 
analyzed or interpreted the data with specific respect to MNRRA.  To 
understand park-specific water quality trends, we compiled thirty years of 
Metropolitan Council monitoring data (1976-2005) for six Mississippi River 
sites, a nearby Minnesota River site, and the Metropolitan Wastewater 
Treatment Plant outflow.  Data showed strong spatial trends, with increasing 
concentrations of nutrients and sediments from upstream to downstream, and 
strong temporal trends, with significant decreases (as per seasonal Kendall 
trend tests) in the flow-adjusted concentrations of most nutrients, total 
suspended solids, and turbidity over the period of record at all sites.  Only 
nitrate concentrations increased significantly over time.  Water quality in 
MNRRA appears highly sensitive to changes in both wastewater treatment and 
tributary inputs.

Keywords: water quality, trends, nutrients, sediments, Twin Cities 
Metropolitan Area

Brenda Moraska Lafrancois
National Park Service
St. Croix Watershed Research Station
16910 152nd St. N
Marine on St. Croix, MN 55047
Ph: 651.433.5953 x35
Fax: 651.433.5924
Email: brenda_moraska_lafrancois@nps.gov 

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