Impaired Waters and TMDL

As the environment becomes increasingly important to Minnesotan's, row-crop farmers are being accused of not being as environmentally friendly and/or impairing the lakes and rivers around their fields with run-off and pesticides.

Minnesota farmers must become very actively involved through MSGA and/or other farm and commodity organizations representing farmers interests on environmental issues. This is especially important because TMDL and Impaired Waters are becoming more and more of an issue for farmers.

TMDL is defined as the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards. TMDL also refers to the process of allocating pollutant loadings among point and nonpoint sources. (A point source is a pollution source that can be pointed to one entity, like a wastewater facility. Farmers are considered non-point sources, non-specific entities).

The Minnesota Pollution Control Agency defines "impaired waters" as a lake or stream where water quality does not support one or more of its beneficial uses — categories which the Clean Water Act (CWA) requires the state to classify their water resources. Examples are drinking water, recreation, industrial consumption, agriculture and wildlife, aquatic life and aesthetics. The CWA requires that states assess their water resources to determine if they meet designated uses. The ones that don't meet the water quality standards are listed as impaired. Five impairments that commonly show up in Minnesota water include Phosphorus, fecal coliform bacteria, turbidity, nitrogen and mercury.

According to the MPCA, for each pollutant that causes a water body to fail state water quality standards, the CWA requires states to conduct a Total Maximum Daily Load (TMDL) study. The studies identify all sources of each pollutant in an affected body of water. How the pollutant source is reduced is determined by water-quality sampling and computer modeling, as well as public input.

The Environmental Protection Agency defines TMDL as "a written plan and analysis of an impaired waterbody established to ensure that the water quality standards will be attained and maintained throughout the waterbody in the event of reasonably foreseeable increases in pollutant loads." Farming practices will be a significant component of the plan.

In the Minnesota River Basin alone there are more than 80 lakes and 84 river reaches with identified impairments, and among the river reaches, there are more than 200 separate impairments, according to the MPCA. Many of the impairments occur during high-flow conditions when field runoff reaches the river. According to the MPCA, the lower Minnesota River TMDL was created in the mid-1980s. It was developed in response to dissolved oxygen concentrations that were significantly below water quality standards and could threaten fish populations. The TMDL included both point source and nonpoint source reduction goals. As a result, the two large Metropolitan wastewater facilities have modified their treatment. In addition, there has been a sustained, basin-wide effort to reduce nonpoint sources of pollution. It has been estimated that there has been a 25 percent reduction in sediments in the river since the TMDL was created. This TMDL is an excellent example of how point sources and nonpoint sources work together to reduce a variety of pollutants after a TMDL is created. The TMDL's set the environmental goals and recommend approaches for improving water quality.

The Minnesota River Basin is just on example of TMDL, and there are many more in other rivers, streams and lakes throughout Minnesota. For more information about TMDL, and how farming in the future may be affected by the Clean Water Act and TMDL's, go to the MPCA Web site.