Monitoring the Thompson Chain of Lakes

The Thompson Chain of Lakes region stretches approximately from Kalispell to Libby. The Chain of Lakes consists of 18 lakes including McGregor Lake, Little McGregor Lake, Lower Thompson Lake, Middle Thompson Lake, Upper Thompson Lake, Horseshoe Lake and Loon Lake.

Visitors enjoy swimming, boating, camping, and water skiing, and the lakes are especially noted for great fishing. Thompson Chain of Lakes State Park also offers some of the most outstanding opportunities for wildlife viewing in northwest Montana.

The Thompson Chain of Lakes Stewardship Coalition (TCLSC) is a non-profit dedicated to protecting the natural beauty of the 18 lakes that makes up the Thompson Chain of Lakes in northwest Montana. The coalition is made up of individuals who share a deep appreciation for this special place. The group promotes conservation, sustainability, and meaningful community engagement. 

The Thompson Chain of Lakes Stewardship Coalition is a nonpolitical neighborhood organization founded in 2022. Their mission is to protect and conserve the land and clean water of The Thompson Chain of Lakes for current and future generations. They hold the Lincoln County Commissioners and Planners accountable to the vision and land use prescriptions clearly identified in the Thompson Chain of Lakes Neighborhood Plan.

The three lakes that TCLSC will be monitoring are important lakes to monitor because they are closed basin spring fed lakes with no inlet nor outlet making them extremely vulnerable to contaminants. Many residents in this community get their only drinking water from the lakes. Those residents with wells, for the most part, have shallow wells of 50 feet or less. There is no water quality monitoring currently being done on any of these lakes and we specifically have no baseline data on nitrogen or phosphorous levels. The spring fed lakes in this system are sinks for sediment as well as contaminants contained in surface runoff and groundwaters. Significant water quality concerns associated with Nitrogen and Phosphorus contamination from septic system effluent was highlighted 29 years ago in the Thompson Chain of Lakes Management Plan and Environmental Analysis.

Due to the high porosity of coarse glacial and alluvial soils found throughout the area, contaminants are able to migrate into shallow gravel aquifers impacting wells and affecting springs that feed the lakes. Because of this hydrology the water system of the Thompson Chain of Lakes is threatened as is the entire watershed and the ecology of this area of Montana per recent hydrological analysis. The lake/land interface in the Thompson Chain of Lakes is perhaps the most sensitive area in terms of water quality. The proximity and intensity of human land uses in this interface may have a significant influence on water quality.

Surface and groundwater quality degradation associated with stormwater runoff, septic system effluent, and pesticide and fertilizer application are ongoing concerns in the Thompson Chain of Lakes area. The cumulative effects of large-scale development on the water resources need to be seriously evaluated when making land use decisions. Scientific data is critically needed to encourage decision makers to consider environmental impacts when evaluating future development near the spring fed basin lakes.

TCLSC's project is designed to provide a scientific baseline and ongoing water quality analysis for residents and for County and State Officials. It will help protect and conserve these vulnerable lakes now and into the future. The benefits to the community are that this analysis will inform residents and others with important water quality information to assure that wetlands, unique fish and wildlife habitats, species of special concern, and other environmentally sensitive areas are protected by protecting the quality of the water. This project will also ensure that water quality and quantity is protected and conserved for public health.

They three lakes to be monitored are spring fed with no inlet nor outlet making all three vulnerable to contaminants. The surrounding area of the 65,000 acres that make up the Chain of Lakes is largely open space and undeveloped. Most of the development is associated with residential cabins and homes along the lake shores of two of the three lakes. Due to the pristine natural forested beauty of the area, it attracts ever expanding demand for development and recreational uses.

Crystal Lake is 183.6 acres, 153 ft at the deepest location, with an average depth 49 feet. There are several seasonal cabins and year-round homes on the lake. There is a FWP public boat launch, and one small, dispersed day use area. Lavon Lake is 16 acres, 92 feet maximum depth, and an average depth 30 feet. Cabins and homes surround the lake and there are no public sites. Horseshoe Lake is 138 acres, maximum depth 134 feet, average depth of 44 feet. There are no cabin nor homes, and one FWP public campground.

To learn more about Thompson Chain of Lakes Stewardship Coalition or Monitoring Montana Waters, click the caption below each organization's logo.