Minnesota River Basin Impaired Waters by Watershed

Impaired Waters in the Minnesota River Basin by Major Watersheds  
Minnesota River Basin Impaired Waters  

What are Impaired Waters?


The Impaired Waters List for the Minnesota River Basin includes the following pollutants or stressors.

Fecal Coliform

A type of bacteria found in the intestinal tracts of mammals. The presence of fecal coliform bacteria in water is an indicator of pollution and possible contamination by pathogens.  Reported in Colony Forming Units/100 mL of sample (CFU/100 mL).

Not all fecal coliform bacteria cause disease, but this relatively simple test is used as an indicator that fecal matter is getting into the waterbody, and that other potentially harmful contaminants may be also be entering the waterbody. The main sources of these bacteria are from animal and human waste. Animal sources of bacteria include feedlot and manure runoff, urban runoff, and wildlife. Improperly treated human waste may come from overflows from sewage treatment systems in cities and towns, unsewered areas with inadequate community or individual wastewater treatment, or a single home with a failing septic system. (MPCA)

Escherichia coli (E. coli)
A type of coliform bacteria present in the gastrointestinal tract of warm-blooded animals.  The concentration of E. coli bacteria is an indicator of the probability of contamination of surface water by microbial pathogens.  Reported in Colony Forming Units/100 mL of sample (CFU/100 mL).

Measures particles in the water, such as sediment and algae. Related to the depth sunlight can penetrate into the water. Higher turbidities reduce the penetration of sunlight in the water and can affect species of aquatic life that survive in the waterbody. Causes of high turbidity include organic matter, algae, sediment and solids that do not settle out of the water; measured in Nephelometric Turbidity Units (NTU).

Common anionic form of chlorine which carries one net negative charge. It is a common anion in many waters. Chlorides may get into surface water from several sources including: rocks containing chlorides, agricultural runoff, wastewater from industries, effluent wastewater from wastewater treatment plants, and road salting.

Fish bioassessments
A bioassessment is an evaluation of the biological condition of a waterbody that uses biological surveys and other direct measurements of resident biota in surface waters. Fish bioassessments evaluate the fish population, the bottom dwelling insects and other invertebrates, and plants or attached algae. Data collected from bioassessments can be used to determine whether the biological health of the waterbody is what would be expected if pollution and other water quality stressors were not causing an effect.

Mercury in fish tissue
Mercury is a highly toxic element that is found both naturally and as an introduced contaminant in the environment. It can be toxic when consumed by animals and humans. Although concentrations in water are very low, mercury accumulates through the aquatic food chain, resulting in high concentrations in fish that can threaten the health of people and wildlife. It is measured in units of nanograms per liter (ng/L) in water and milligrams per kilogram (mg/Kg) in fish. Sources of mercury include weathering of the earth's crust, the burning of garbage and fuels, and industrial emissions.

Fish Consumption Advisory
An advisory issued by a government agency recommending that the public limit their consumption of fish. Advisories are issued to limit exposure to toxic substances in the fish that have the potential to impact human health. A fish consumption advisory is prepared annually by the Minnesota Department of Health. Fish caught from selected lakes and streams are tested for toxic substances (mercury, sometimes PCBs and dioxins). Many of the lakes tested have restrictions on fish consumption due to high mercury levels. PCBs and dioxin levels in fish have also resulted in suggested restrictions on fish consumption in some lakes and streams. Other states and the federal government also issue advisories.

Mercury Water Column
(see Mercury above) The water column is a conceptual column of water from surface to bottom sediments

PCB in Fish Tissue
Polychlorinated biphenyls (PCBs) are a family of man-made chemicals that contain over 200 individual compounds with varying levels of toxicity. PCBs were widely used as coolants and lubricants in transformers, capacitors, and other electrical equipment and various inks, adhesives, and paints until they were banned in 1977.

Although PCBs are no longer manufactured, exposure still occurs as a result of historical contamination. Eating contaminated fish is a major source of PCB exposure for humans because PCBs bioaccumulate in some species of fish found in contaminated waters. These compounds are highly toxic to aquatic life, persist in the environment for long periods of time, and are bioaccumulative. PCBs are suspected carcinogens, and are linked to infant development problems.

PCB in Water Column
(See PCB above). Beyond fish tissue, PCB is also measured in the water column -- a conceptual column of water from surface to bottom sediments

Oxygen, Dissolved 2,5 
The amount of oxygen dissolved in water. Most fish and beneficial aquatic insects "breathe" oxygen dissolved in the water column. Dissolved oxygen is the oxygen necessary to maintain a healthy ecosystem for fish and other aquatic life in a waterbody. Low DO can be harmful to aquatic organisms. Oxygen concentrations in the water column fluctuate under natural conditions, but prolonged episodes of depressed dissolved oxygen concentrations of 2 mg/L or less can result in "dead" waterbodies. Measured in mg/L or ppm.

Ammonia (Un-ionized) 2,5
Ammonia is an inorganic nitrogen compound. In water, ammonia levels in excess of the recommended limits may harm aquatic life.

Acetochlor is a member of the class of herbicides known as chloroacetanilides. It is primarily used to control weeds in cornfields. Herbicides containing acetochlor are used widely in Minnesota and marketed as Harness, Surpass and Keystone, among other brands. Measured in µg/L or ppb.

Nutrient/Eutrophication Biological Indicators
Eutrophication is the aging process by which lakes are fertilized with nutrients. Natural eutrophication will very gradually change the character of a lake. Cultural eutrophication is the accelerated aging of a lake as a result of human activities.

MPCA Impaired Waters Glossary
MPCA Glossary
Virginia Cooperative Extension
Water on the Web Glossary

Learn more about Minnesota’s Impaired Waters on the MPCA website




This page was last updated 8/08