WATER QUALITY

Lac Manitou is an oligotrophic lake: naturally low in plant life with lots of oxygen in deep waters to support fish life. This determination comes from testing down by the Ministère du Développement durable, de l’Environnement, de la Faune et des Parcs (MDDEFP).

Without a lot of plant life, our lake remains crystal clear; when it is calm, you can see right to the bottom. No weeds to get caught in while swimming, nothing to snag your boat’s motor. An oligotrophic lake offers an oxygen rich environment which makes it a welcoming habitat for many fish species including lake trout.

These are some of the qualities that draw us to Lac Manitou and they are qualities that can change quite easily. Lakes evolve but natural is very slow. But humans can accelerate change to super speed. Anything that adds nutrients to the lake depletes oxygen and increases the potential for plant growth: soap and detergent, pesticides, herbicides, a leaking septic system, boat fuel, shoreline modifications.

The AALM monitors the health of the regions’ three lakes: Lac Manitou, Lac de la Grise, and Lac Fer-à-Cheval. We test for fecal coliform, clarity and nutrient levels. We also do PH testing in Manitou.

The most recent testing results show that our lakes are in good condition, although some trouble spots were found. Here’s a synopsis of the report: Water Quality in Our Lakes: 2024 Results.

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)