A healthy lake
We must ensure that the lake is protected from contamination by watermilfoil, storm sewers, shoreline erosion and sediment agitation
An initial survey of the extent of aquatic seaweeds was conducted in 2008, followed by controlled observations in 2012 and 2017. The area of floating seaweeds inventoried in Lac des Sables increased by 290% between 2008 and 2017. In 2017, an “aqua scope” was used to map submerged seaweed beds. Biofilia’s 2017 analysis shows that seaweeds cover 22% of the Lake’s shoreline between 0 and 3 meters deep (swimming area).
At moderate levels of abundance, seaweeds are attractive and environmentally necessary, being an important part of the ecosystem. Their presence in the lake is quite natural and normal. However, when they are too abundant, they become a real problem.
The increase in seaweed coverage of 290% over 9 years in Lac des Sables constitutes accelerated aging. The reasons for this increase are diverse; nutrient supply, the agitation of sediments that are at the bottom of the lake by boats that produce large waves, and the spread of seaweed by boats with propellers.
We need to significantly slow this spread of aquatic seaweed.
Watermylfoil, the most important danger
Fortunately, analyses indicate that watermylfoil is not yet present in Lac des Sables. It already contaminates 132 lakes and 16 rivers, including 40 lakes in the Laurentians (2018) such as Trout Lake and Quenouille Lake. It is an invasive exotic aquatic plant with a great capacity for adaptation. It disturbs natural habitat and impairs water quality.
Natural predators of this plant are very rare and it has an additional advantage: it can reproduce by fragmentation of the stem. Thus, a small piece of severed stem can take root and give birth to a new plant. Fragments can be carried by the current, by boats and by animals. As a result, in a very short period of time, you can quickly end up with gigantic seaweed beds that destroy ecosystems.
Only one solution – prevention
Mandatory washing of 100% of boats and trailers before entering the lake is the only known solution. Even today, no effective way has been found to solve the problems of lakes with watermylfoil.
Call to action
Make sure all boats and trailers, including fishing boats, personal watercraft, etc. are washed at the washing station before entering the lake. See the document here: Waterfront areas, pesticides and fertilizers – City of Sainte-Agathe-des-Monts
The supply of sediment to the lake must be controlled to ensure the survival of the lake.
Lac des Sables is highly urbanized. Ensuring its health for future generations is a major challenge.
Analysis by the biologist firm (Biofilia) shows that storm drains around Lac des Sables are direct sources of pollution to the lake. In fact, storm drains are one of the main sources of contamination of the lake.
Storm drains carry contaminants such as phosphorus, suspended materials and fecal coliform bacteria to the Lake. In high concentrations these contaminants affect water quality, especially during rainy periods. The constant supply of pollutants on a daily basis inevitably causes pollution of the lake’s waters.
How can these contaminants be prevented from polluting the lake? The solution is to install sediment collectors at the end of storm drains to prevent them from spilling into the lake.
Around Lac des Sables, there are 25 storm drains (8 major and 17 minor) flowing into the lake, many in the downtown area.
By September 2019, 4 sediment collectors had been installed by the City to correct three major storm sewers and 1 minor. The last sediment collector was installed in 2012. The next one is scheduled for 2020.
See the locations of storms drains below:
Let’s ask the City of Sainte-Agathe-des-Monts to make it a priority – Contact us – City of Sainte-Agathe-des-Monts
We need to limit shoreline erosion to keep the lake healthy. Shoreline vegetation is ecologically important to the Lake.
Erosion in the Lake
Every year, larger and larger portions of land disappear into the Lake.
Shoreline erosion is the phenomenon of material loss caused by the flow of water on the banks. This water flow may be a wave (caused by wind, a natural current, a boat), runoff (rain accentuated among other things by the degradation of lake shorelines) or a phenomenon of water variation (high/low water levels).
The presence of boats on the Lake such as “wake surf” and “wake board” boats contributes significantly to the erosion of the banks. A 2013 study by the University of Quebec in Montreal (UQAM) shows that these types of boats have a significant impact on shoreline erosion when they travel within 250 meters of the shore. Unfortunately, the configuration of Lac des Sables does not allow compliance of this standard for these types of boats. Currently, federal navigation regulations allow this type of boat to navigate on the Lake. Out of respect for the health of our Lake, we ask that these activities be carried out only in the center of the lake, south of l’Ile aux Bleuets between Major Bay and Viau Bay.
Find out more: Project to assess the impact of waves created by wakeboat boats on the shores of Lakes Memphrémagog and Lovering
See the map produced in 2018 for the location of erosion sites.
Deforestation of the shoreline
A 10 to 15 meter waterfront strip must be preserved under the MDDELCC Shoreline, Coastal and Floodplain Policy.
The waterfront strip is a belt of vegetation along the waterfront. It is measured from the high water line. Its width varies depending on the slope of the bank.
In 2008, 42% of the shores of the lake were considered disturbed or severely disrupted by human activity. We are talking about roads, cement docks, grassy land up to the lake and other human creations… A major shoreline regeneration program was then set up by the Municipality. Residents had three years to reforest the banks. This program has proven to be extremely beneficial, as can easily be seen on the shores. The City has also carried out work on areas under its responsibility. An update of all this work is planned for 2020.
Vegetation on the shores are important ecologically in the following ways:
– Water filtering
– Rooting to fix the soil
– Erosion barrier
– Recycling nutrients carried in water
– Habitat of a multitude of plants and animals, several of which are threatened
Learn about regulations: Waterfront bands, pesticides and fertilizers
Sediment agitation contributes to the spread of aquatic seaweed.
The “wake surf” and “wake board” boats cause huge waves that cause significant sediment agitation at the bottom of the lake. Agitation of the sediment contributes greatly to the proliferation of aquatic seaweeds.
In 2015, a comprehensive study by Laval University concluded that “wake surf” and “wake board” boats had an excessive impact on sediments when the depth is less than 5 meters.
Navigation map showing the depths of Lac des Sables.
It is mandatory to decontaminate all boats before entering into the water.
It is mandatory that all boats and trailers, without exception, be washed every time they enter the lake.
Washing is necessary to prevent the watermylfoil from entering the lake and to decontaminate the boats. This washing service is free for residents of the City of Ste-Agathe-des-Monts and is easily accessible at the boat ramp.
Article 3: decontamination of boats:
Ref: Regulation number 2013-M-144-4 Article 3
Check with the boat ramp: 819-326-7698