Management

Water Quality Monitoring

The systematic collection and analysis of water samples and measurements to track lake health over time and detect changes in water quality.

What It Means for Your Lake

Water quality monitoring is the foundation of lake management and the data source behind every LakeQuality report card. In Minnesota and Wisconsin, lake monitoring is conducted by a network of state agencies, federal programs, county governments, lake associations, and trained citizen volunteers. The primary monitoring parameters include Secchi depth (transparency), total phosphorus, chlorophyll-a, dissolved oxygen profiles, temperature profiles, pH, conductivity, and total suspended solids. Most monitoring occurs during the summer index period (June through September), when thermal stratification is established and water quality conditions are most relevant to recreation. The Minnesota Pollution Control Agency (MPCA) operates the Citizen Lake Monitoring Program (CLMP), one of the oldest and largest volunteer monitoring networks in the nation, with over 1,000 volunteers taking weekly Secchi readings on approximately 1,200 lakes each summer. Wisconsin DNR runs a similar program through the Self-Help Monitoring Program and the Citizen Lake Monitoring Network. Professional monitoring by agency staff provides more comprehensive data including nutrient chemistry and biological assessments, but covers fewer lakes, the MPCA directly monitors approximately 200 to 300 lakes per year on a rotating basis. The EPA Water Quality Portal aggregates monitoring data from all federal, state, tribal, and volunteer sources into a single searchable database, which is the primary data source used by LakeQuality. Long-term monitoring records are essential for detecting water quality trends because lake conditions vary naturally from year to year based on weather patterns, a single year of data cannot distinguish natural variability from actual change. The most valuable monitoring datasets span 10 to 30 years or more and reveal whether lakes are improving, declining, or stable over time.

Frequently Asked Questions