Water Quality

Water sampling tells our quality story

2022 RMB Lakes Database results.

More information about the Trophic State Index of Leech Lake can be found in the LLA Spring 2023 newsletter.

Background: Every summer since 2008 Leech Lake Association volunteers have collected water samples and taken Secchi disc readings from four places in Leech Lake: the main basin north of Stony Point, Agency Bay, Walker Bay and Kabekona Bay. These samples are analyzed to give us important information about the overall health of the lake. The tables linked below contain data about the following indicators:

TP or Total Phosphorous: A nutrient needed for plant growth. Phosphorus can enter the lake during run-off from fertilizer, manure or through seepage from leaking septic and holding tanks.
Chia or Chlorophyll-a: The pigment that makes plants and algae green. Chlorophyll-a is measured in lakes to determine algae concentration, or how green the water is.
Secchi Disc: A measure of water clarity that can indicate the overall health of a lake. A white metal disc is lowered into the water on a segmented rope until it can’t be seen anymore and raised to the point where it can be seen. The depth of the disk to the surface of the water is the Secchi Depth.
TSI or Trophic State Index: A measurement of overall lake productivity (nutrient enrichment). The overall TSI of a lake is the average of the TSI for phosphorus, chlorophyll-a and Secchi Disc.

Trophic States are deemed divisions of a continuum in phosphorus and algal concentration. The TSI ranges from 0-100. 0-30 is Oligotrophic, where water is very clear, phosphorus is low, and algae is sparse. This might describe a very deep, cold water lake, with oxygen throughout the year at the bottom of the lake. A TSI of 30-50 is an in-between stage where the number of aquatic plants algae increases due to more available phosphorus. Leech Lake fits within this range, though TSI may vary some between the basins. Agency Bay, for example, had an annual mean of 40.3 in 2008 and 41.4 in 2020.

With the appearance of Zebra mussels in the lake, water clarity will likely increase. How this will impact the fish population is not well known. LLA will continue to collect samples and fund analysis of the phytoplankton population in Leech Lake. Continuing these studies over the next few years will provide the DNR with the information it needs to monitor the food chain and its effect on the Leech Lake fishery as the lake reacts to Zebra mussels, other invasive species, and changes to the lake chemistry due changes in phosphorus and chlorophyll-a levels.
If you are interested in volunteering to help collect water samples or want to learn more about LLA efforts in this area, contact Tom McGovern at tommcgovern2@gmail.com (Water Quality chairperson).

Watersheds: A look at the big picture
Minnesota has 80 major watersheds. Leech Lake is part of the Leech Lake River watershed, which is consists of approximately 854,659 acres (1,335 sq. miles) in the northern part of the Upper Mississippi River Basin. The watershed includes parts of Beltrami, Cass and Hubbard Counties, as well as the Leech Lake Reservation (Leech Lake Band of Chippewa). The Leech Lake River Watershed has 277 total river miles and contains over 750 lakes with a total acreage of 166,374.

Extensive work has been done to document and monitor the health of the water in our watershed. LLA actively participates in water quality monitoring through the Citizen Lake Monitoring Program.

According to the Minnesota Pollution Control Agency, the surface water resources within this watershed meet Minnesota water quality standards for conventional pollutants (not including mercury). These resources are prized, and their protection is vital in sustaining the local economy and natural heritage and character of this watershed.

The major threats to the watershed include:

Loss of shoreline and aquatic habitat due to development.
Population growth of up to 60% projected for the watershed by 2030, according to Minnesota State Demographers.
Increased nutrient, contaminant, and sedimentation loading from stormwater runoff from development and other non-point sources.
Loss of biodiversity due to competition from invasive species.

Much is being done to understand how we can protect the watershed and preserve our water quality for future generations. Explore the MPCA website and the many resources found there.

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HISTORY OF WATER QUALITY SAMPLES