Long Prairie River Watershed - Low Dissolved Oxygen: TMDL Project

Minnesota's Impaired Waters and TMDLs


Low dissolved oxygen (DO) due to high levels of ammonia impair water quality in the Long Prairie River. The entire length of the river was listed as impaired in 2002. Low dissolved oxygen occurs primarily during low-flow conditions, when the volume and current of the water in the river are less than average. The MPCA hired a consultant to complete a modeling study of the Long Prairie River. Results from the TMDL study indicate that, with ammonia reductions, it is possible to meet the dissolved oxygen standard in the Long Prairie River during low flow conditions. The TMDL report was approved by the EPA on August 5, 2005.

Map and location

The Long Prairie River flows approximately 100 miles from its headwaters at Lake Carlos to its outfall near Motley into the Crow Wing River, and eventually, to the Upper Mississippi River. 


TMDL report and implementation plan

The Long Prairie Dissolved Oxygen Implementation Plan 2007 was completed in 2007. Since that time, Todd County, along with other partners have received over $845,000 in Section 319 Grants, and have matched with cash or in-kind another $1.3 million.
Flagship projects in this area included bank stabilizations using engineered streambarbs at locations along the river. Changes to vegetation, hydrology and natural channels have caused many segments of the river cut into banks at the loss of 10-20 feet per year. Streambarbs allow river current energy to be redirected and the barbs enable sediment deposition where banks have eroded.
The Long Prairie River Watershed is dominated by agriculture, and the sand and gravel which outlines the river valley is highly permeable. The resulting higher infiltration rates make animal waste containment a top priority. Farm­yard fixes are engineered to store dirty water and ma­nure in place until they can be properly field applied. This keeps nutrients locked up and river life in balance where farm site water and river waters converge.
In the last ten years alone nearly 70 projects have been completed with the help of MPCA 319 funds. This fund­ing source combined with private, public and land­owner dollars has resulted in hundreds of conservation projects all along the river. These projects have result­ed in significant reductions of many pollutants such as nitrogen, sediment and phosphorous.
Projects over the years as diverse as rotational grazing plans, livestock exclusion fencing projects, agricultural waste pond closures, alternative livestock watering sources, nutri­ent management plans, minimum tillage, riparian grass buffers, storm water control – rain gardens, reforestation and riparian tree planting projects and bank stabilization and shore land erosion control projects have helped restoration efforts on this unique river.


Information contact

Anna Bosch
Watershed Project Manager
MPCA Brainerd Regional Office
7678 College Rd, Suite 105, Baxter, MN 56425