Total Daily Maximum Load (TMDL)

What is a TMDL?

The federal Clean Water Act requires states to adopt water quality standards to protect lakes, streams, and wetlands from pollution. The standards define how much of a pollutant (bacteria, nutrients, turbidity, mercury, etc.) can be in the water and still meet designated uses, such as drinking water, fishing, and swimming. A water body is "impaired" if it fails to meet one or more water quality standards.


To identify and restore impaired waters, Section 303(d) of the Clean Water Act requires states to:

  1. Assess all waters of the state to determine if they meet water quality standards
  2. List waters that do not meet standards (also known as the 303d list) and update every even-numbered year
  3. Conduct TMDL (total maximum daily load) studies in order to set pollutant reduction goals needed to restore waters


Federal and state regulations and programs also require implementation of restoration measures to meet TMDLs. For more information on TMDLs, please visit the MPCA website.


TMDLs in Benton County


Major Watershed Restoration and Protection Project (MWRPP)

What is a MWRPP?

The Major Watershed Restoration & Protection Project (MWRPP) is a State developed 10-year cycle program which provides an approach for State-wide assessment of water quality and aquatic life. The Watershed approach is designed to intensively monitor streams and lakes within a major watershed to determine the overall health of the water resources, identify impaired waters, and identify those waters in need of additional protection efforts to prevent impairments.


A watershed is the area of land that all drains to the same body of water. In Minnesota there are 81 major watersheds. Through this program monitoring sites are placed to provide methodical spatial coverage within the study watershed therefore leading to a more thorough assessment of main stem rivers and their tributaries. The goal of the new 10-year cycle is to address all impairments within 4-5 years from the start of monitoring. The next four to five years would be used to implement BMPs and other watershed restoration practices to address impaired waters. The whole cycle is then repeated. This effort will help coordinate the efforts of local, state and federal entities to most effectively manage watershed resources. Most importantly this process will provide a communication tool that will inform stakeholders, engage volunteers, and activate citizens. To learn more please visit the MPCA's Watershed Approach webpage.


Steps of the MWRPP are as follows:

  1. Monitor and gather data and information (Years 1-3)
  2. Assess the data (Years 1-3)
  3. Establish implementation strategies to meet standards (Years 1-3)
  4. Implement water quality activities (Years 4-10)


MWRPPs in Benton County