Enviro Lac Gauvreau
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Enviro Lac Gauvreau

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Water quality test results

Enviro Lac Gauvreau tests the water for two different purposes. In the summer months, we test the lake water for the presence of E.coli (Escherichia coli) to determine safety for swimming. We also collect data that helps us track the aging of the lake to detect if the otherwise natural process is being sped up by human factors.
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Is the lake safe to swim in?
Presence of E.coli is also used to determine standards for swimming and drinking water. The amount of E.coli in the water helps us determine if the water is safe for us to swim in. It can also help determine the presence of faulty septic systems. E. coli is a type of bacteria that lives in the intestines of people and animals.

Generally, the quality of the lake water for swimming has been excellent over the last few years. Algae blooms can also be an issue for swimming safety if the type of algae is the blue green algae and contains cyanobacteria, which is toxic. When we suspect algae may be blue green algae, we investigate. Over the years we have not yet detected the toxic version of blue green algae.


CLICK ON TABS BELOW TO VIEW ANNUAL E.COLI TEST RESULTS

    science 2024 water quality test results
    E.coli testing for swimming safety (Summer 2024)
    August 26, 2024 Test Results Show Improved Water Quality

    Enviro Lac Gauvreau (ELG) regularly tests several locations in the lake for E.coli. The map above shows the E.coli levels for each spot tested.

    Test results from August 26th show reduced E. Coli levels at Baie Ste-Anne resulting in swimming advisory being called off.

    Results received from the lab showed that samples taken on August 19 indicated levels that were unusually elevated. Samples taken in Baie Ste-Anne were well above the level for safe swimming according to the standards set by the Province of Quebec. Residents were advised to avoid swimming in this area, as well as around the mouth of Parent Creek.

    We suspect that these high levels of E.coli were the result of run-off from recent rainstorms. We have also reported the dangerous levels in Parent Creek to the Municipality.


    LAC GAUVREAU TEST RESULTS FOR JUNE, JULY & AUGUST 2024

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    Testing done by: MicroB in Hull

    Province of Québec Standards for Swimming (Units: CFU/100ml)
    CFU = Colony Forming Units
    0 - 20: Excellent
    21 - 100: Good
    101 - 200: Acceptable
    201 - +: Not recommended
    science 2023 water quality test results

    LAC GAUVREAU TEST RESULTS FOR JUNE, JULY & AUGUST 2023

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    Physical-chemical data - Summer 2023
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    science 2022 water quality test results

    LAC GAUVREAU TEST RESULTS FOR JUNE, JULY & AUGUST, 2022

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    science 2021 water quality test results
    2021 water quality test results
    Thanks to Municipal funding, a full battery of water quality tests was done last summer, and the results have now been released. Samples were taken on July 5th, August 5th, and mid September, 2021. Volunteers also collected E. Coli samples, done annually, to get a complete profile of Lac Gauvreau's overall health. Following scientific advice and analysis, the results are in! Credit goes to the volunteer test team: Emma Doorly, Barb Booth and Susan Peck. Similar tests will be conducted this summer.
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    Table - Trophic Status

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    The Enviro Lac Gauvreau Association has released the final results and interpretations of water quality tests that were conducted during the summer of 2021, using the "RSVL" Water Quality Sampling Protocol. It took until now to publish this report because the 2021 results are difficult to compare with results from earlier years, since samples were not taken in the same places as previously used. Consequently, RSVL has directed Enviro Lac Gauvreau to measure only at the deepest spot (the “pit”) starting in 2022.

    Phosphorus levels high

    The 2021 phosphorus numbers are roughly the same as in the past. The combination of the different variables analyzed shows that Lac Gauvreau had, even some fifteen years ago, the characteristics of a relatively old lake (i.e. meso-eutrophic).

    The lake is significantly enriched with phosphorus (average concentration of 21 ug/L) and the level of chlorophyll A is very high (average concentration of 13.3 ug/L). The water in the lake is very cloudy, with an average transparency of 1.8 meters.

    Dissolved organic carbon (DOC) concentration of approximately 8 mg/L was measured a few times in two bays in 2021. Although this was not measured at the pit, it indicates a very strong colouration of water, which could have a major impact on transparency.


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    Map of the location of the sampling stations at Lac Gauvreau from 2002 to 2021
    *Bélisle stream, located north of Parent stream, is not shown here on the map


    Swimming is safe in most areas

    The average values for the vast majority of sectors are representative of "excellent" or "good" water quality, suitable for swimming, with the exception of Parent and Bélisle creeks. For these sectors, the maximum values observed exceed the criteria allowing indirect contact with water, such as with boating and fishing, because the water is considered unhealthy. The beach at the Whippoorwill Campground is the most effected because of its close proximity to the Parent Creek outlet.

    Blue green algae blooms can render perfect swimming water unsafe, even when the e-coli count is very low. So, in the event of a blue green algae bloom, the quality of the water may become unsafe for swimming.
    As they do annually, Enviro Lac Gauvreau volunteers collect samples that assess for E. Coli levels at various locations on the lake and in Parent Creek. See the map above where locations A through D indicate Faecal Coliform sampling only. Annual testing has consistently yielded average "Good" to "Excellent" results. The 2021 E. Coli measurements were no exception. The net results of these tests show that Lac Gauvreau continues to be safe for swimming.

    Recommendations - Lake health

    Enviro Lac Gauvreau must follow the protocols of the Voluntary Lake Monitoring Network (RSVL) in order to assess the health of the lake in the long term.

    • In order to determine the state of health of a lake, the concentrations of total phosphorus and chlorophyll A, as well as the transparency of the water, must be measured at the lake pit (deepest place) in the first meter of water.
    • Samples must be taken at a certain frequency. For example, sampling should be done three times during the summer.
    • Water transparency must be assessed at least ten times between the months of May and October (MELCC, 2022).
    The monitoring of Lac Gauvreau as part of the RSVL program in 2022 will make it possible to carry out these analyses.


    science ARCHIVED - E. Coli Tests
    science ARCHIVED - Municipal tests
    science ARCHIVED - H2O des Collines tests
Provincial tracking of water quality and aging of lakes
Enviro Lac Gauvreau participates in a voluntary lake testing program run by the Province of Quebec called Quebec Volunteer Lake-Monitoring Program or in French: “Réseau de surveillance volontaire des lacs” (RSVL).

RSVL helps lake residents monitor water quality and degree of aging of their lakes. Specifically, the program measures levels of total phosphorus (TP), dissolved organic carbon (COD) and chlorophyll A (chl a).

Following the RSVL protocol, volunteers take water samples near the deepest part of the lake (site #2 on the map). This is done once in June, July and August. Transparency measurements are also taken using a Secchi disc once every two weeks. RSVL then arranges for pick-up of the samples, analysis, and production of reports.

> See analysis of RSVL data on the health of lakes across Quebec in the Journal de Montreal

> The Province of Ontario has a similar lake testing program and useful information on their website
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Map showing six water testing sites.
Is the lake prematurely aging?
A detailed description of the aging process, often referred to as eutrophication, and how to measure it, is available on the Government of Quebec’s website. La page Web est aussi disponible en français.

In a nutshell, eutrophication is the process of aging that naturally occurs in lakes. The process can be sped up by human intervention such as too many nutrients getting in the lake from septic systems or use of fertilizer nearby.

The earliest results of Total Phosphorus we have for Lac Gauvreau are from 2002. Between 2002-2005, the concentration of Total Phosphorus in the deepest part of the lake averaged 20 (µg/L). These test results were collected by the University of Ottawa. These results classify Lac Gauvreau as Mesoeutropic.

Since 2022, Lac Gauvreau has been part of the Quebec Volunteer Lake-Monitoring Program or in French: “Réseau de surveillance volontaire des lacs” (RSVL). Between 2022-2024, the concentration of Total Phosphorus in the deepest part of the lake averaged 14 (µg/L), with annual results ranging between 11 - 17 (µg/L). These results classify Lac Gauvreau as Mesotrophic, a slight improvement from testing in the early 2000s.

Total Phosphorus in other parts of the lake has been measured and was higher than these averages. In particular, Parent Creek from Chemin Kennedy to the place where the water enters the lake has consistently been measured as eutrophic.

A concentration of Total Phosphorus that is about 35 (μg/L) denotes a lake that is eutrophic. A eutrophic lake has excessive aquatic vegetation, poorly oxygenated water, a muddy bottom and low biodiversity. The water in a eutrophic lake is warm and turbid (which is the opposite of clear or transparent).




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