Show All Lake Monitoring
The Minnesota Pollution Control Agency (MPCA) conducts and supports lake monitoring for a variety of objectives. One of our key responsibilities is to monitor and assess lakes in Minnesota to determine whether or not these lakes support their designated uses. This type of monitoring is commonly referred to as “condition monitoring.” While the MPCA conducts its own lake monitoring, local partners (SWCDs, watershed districts, etc.) and citizens play a critical role in helping us because their efforts greatly expand our overall capacity to conduct condition monitoring.
To this end, the MPCA coordinates citizen volunteer monitoring through the Citizen Lake Monitoring Program (CLMP), and manages Surface Water Assessment Grants given to local groups to monitor lake water quality. All of the data from these activities are combined with our own lake monitoring data to assess the condition of Minnesota lakes. Lake condition monitoring activities are focused on assessing the recreational use-support of lakes and identifying trends over time.
The MPCA also assesses lakes for aquatic consumption use-support, based on fish-tissue and water-column concentrations of toxic pollutants. Lake characteristics vary by region: in the northeast, lakes tend to be deep, clear, and low in nutrients; in the south and western parts of the state, lakes tend to be shallow, nutrient-rich basins.
In 2009, the MPCA began focusing its condition monitoring effort following the rotating 
watershed approach adopted by the agency’s stream monitoring programs. There are 81 major watersheds in Minnesota, and the MPCA has established a schedule for intensively monitoring lakes and stream reaches in six to eight of them annually.
With this strategy, we will cycle through all 81 watersheds every ten years. By intensively monitoring lakes and streams within a given watershed at the same time, the lake and stream data can be considered together to provide a more comprehensive picture of water quality status and a determination can be made regarding how best to proceed with development of restoration and protection strategies.
MPCA Lake Monitoring
The MPCA monitors approximately 100 lakes each year. Each lake is sampled monthly from May to September for a period of two years. The primary focus is on collection of total phosphorus (nutrient), chlorophyll-a (pigment in algae), and Secchi depth (distance light will travel in water). With this information, it is possible to determine the condition of the lake, commonly referred to as the “trophic status.”
Nutrient levels drive the productivity of the lake. An increase in nutrients often leads to an increase in plant or algal growth and a decrease in clarity. In general, high nutrient levels increase the likelihood that nuisance algal blooms will grow and that lakes will not meet aquatic recreational uses; however, there are sometimes other factors at play that also must be considered (i.e., tea-stained lake water decreases lake transparency, independent of nutrient levels).
For this reason, staff also collects information on water color, suspended solids, temperature, dissolved oxygen and a number of other parameters. After a lake has been monitored for a minimum of two years, the water chemistry data are used to assess its condition. The water quality data and the results of the condition assessment are incorporated in a variety of products, including lake assessment reports, status and trend/update reports and fact sheets.
The MPCA uses the following Standard Operating Procedure (SOP) when conducting its lake monitoring:
Citizen Lake Monitoring Program
In addition to monitoring lake water quality, the MPCA also coordinates the Citizen Lake Monitoring Program. Through this program, citizen volunteers make simple measurements of lake water transparency that help determine the condition of lakes.
Surface Water Assessment Grants
Local groups also monitor lake water quality. Since 2007, the MPCA has distributed Surface Water Assessment Grants to local partners, such as water conservation districts, watershed districts and non-profit groups.
Remote Sensing
Researchers from the University of Minnesota's (UMN) Remote Sensing Laboratory have been developing satellite-based approaches to monitor water resources. In 2003, Legislative Commission for Minnesota Resources funding allowed the MPCA and the UMN to partner on a project that paired citizen-collected Secchi disk data with Landsat satellite images to determine water clarity of all lakes across Minnesota greater than 20 acres in size.
This partnership has continued with additional funding from the passage of the Clean Water Legacy Act. The MPCA uses this remote sensing information to evaluate lakes that are inaccessible or difficult to monitor repeatedly (e.g., lakes within the Boundary Waters Canoe Area Wilderness). The fact sheet below describes the remote sensing technology in more detail. The Remote Sensing of Water Resources Web site also provides a wealth of information, including Lake Browser, which is a fantastic online, interactive lake water clarity mapping tool based on satellite data from 1990, 1995, 2000 and 2005.
Satellite Estimation of Minnesota Lake ClarityAssessing the Condition of Minnesota Lakes
All of the water quality data from the MPCA’s monitoring activities, and those of citizen volunteers, other state agencies, and local groups are gathered together and used to assess the condition of Minnesota lakes. Lake water quality data are compared to state and federal water quality standards to determine if each lake is fully supporting or not supporting those standards set for recreational use (e.g., swimming, wading, etc.).
Lakes not supporting aquatic recreational use are termed ‘impaired’ and are placed on a list biennially. A lake placed on the impaired waters list is required to be intensively researched through a Total Maximum Daily Load study to determine the source and extent of the pollution problem. The study also requires the development of a restoration plan.
The MPCA details its assessment findings in Lake Water Quality Assessment Reports. Lake assessment reports also include information on lake morphometry, trophic status and on trend analysis, if available.
Lake Water Quality Data
Water quality data collected by the MPCA, citizen volunteers and local group partners are stored in a federal repository for water quality data known as STORET . This data can be viewed through two separate applications: the Lake Water Quality Summary database and the Environmental Data Access page.
Special Projects
The MPCA occasionally collaborates with other national, state or local partners on special research studies. In 2007, the MPCA participated in a national study funded by the U.S. EPA called the National Lake Assessment Project . The study is yielding a variety of interesting findings about water quality patterns in lakes nationwide.
The MPCA is also involved in a long-term, collaborative monitoring effort that is being led by the Minnesota Department of Natural Resources called the Sentinel Lakes project. The MPCA is a partner in this effort, with a primary focus on collection and assessment of water quality data for the Sentinel lakes.
