Each summer, the AALM Environment Committee monitors the health of our lakes. The 2024 results show that our waters remain generally clean, though some sites need ongoing attention.

Fecal coliform levels, a measure of bacterial contamination, were mostly excellent across Lac Manitou, Lac de la Grise, and Lac Fer-à-Cheval. On Manitou, nearly all sites were below 10 counts per 100 ml, well within the “excellent” category. Only one location, in Townsend Bay, showed a higher reading (68), which dropped back to safe levels on retesting. At Fer-à-Cheval, results were more variable, ranging from 60 to 120 counts—classified as “good” to “passable.” The Grise remained excellent, with all sites between 3 and 10 counts.

Water clarity, measured with a Secchi disk, remained stable. Manitou averaged 6.8 m, essentially unchanged from last year’s 7 m. Fer-à-Cheval averaged 2.4 m, consistent with 2023. Data for the Grise were unavailable this year.

Nutrient levels tell another part of the story. At Fer-à-Cheval, dissolved organic carbon and chlorophyll (an indicator of algae) were higher than in 2023, while phosphorus was lower. At the Grise, results showed low phosphorus and modest algae levels, consistent with healthy water.

Finally, pH testing on Manitou showed a neutral reading of 7—typical for the Laurentians and favorable for loons.

Overall, these results confirm that our lakes remain in good condition, but they also remind us that careful monitoring and responsible shoreline practices are essential to keep them healthy for the future.

Below are links to the raw data collected over the years (some are pdfs and some are xlsx:

Water Quality Report 2024

Lac Manitou Water tests 2012-2023

Lac de la Grise Water tests 2012-2023

Lac Fer-à-Cheval Water tests 2012-2023

Water tests 2016 (PDF)