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Enviro Lac Gauvreau

UPDATE: August water quality test results released

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September, 2022 UPDATE—Results of the third set of water quality samples collected in August have been released. Our Association's sampling program measures 1) Total Phosphorus (TP) and 2) bacteria (E.coli) levels to determine safety for swimming. The next set of samples will be collected in the fall. Welcome our water testers as they go about their volunteer job.

Results of the first set of full RSVL test samples conducted in June 2022 have been released. More samples will be taken as summer progresses, and analysis/verdict will be available only at the end of the season. Enviro Lac Gauvreau is now fully supported by the “Réseau de surveillance volontaire des lacs” (RSVL).

> See the full report below

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    science 2022 water quality tests underway
    Results of THREE sets of water quality samples done by Enviro Lac Gauvreau volunteers


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    • E.coli - Bacteria (E.coli) samples from all lake testing sites in June, July and August indicate levels well within those considered safe for swimming. Although Parent Creek levels are extremely high, the E.coli reading at Site 5 at the creek's outlet into the lake is low.
    • Total Phosphorus (TP) - Sampling from three sites in June indicated a range from 17 to 20 (μg/L), the highest being in Parent Creek (Site 6). July and August results from only two locations (Sites 5 and 6) show that warmer temperatures and greater boating activity may have resulted in the much higher phosphorous levels, doubling in Parent Creek.
    • According to the table below (source), Total Phosphorus (TP) levels place Lac Gauvreau at the threshold between Mesotrophic and Eutrophic. Mesotrophic lakes have an intermediate level of productivity. These lakes are commonly clear water lakes and ponds with beds of submerged aquatic plants and medium levels of nutrients. Eutrophic lakes have high biological productivity with excessive levels of nitrogen and phosphorus that support an abundance of aquatic plants and algae. Occasionally, an excessive algal bloom will occur.
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    Results of the first set of full RSVL test samples conducted in June 2022 have been released. According to RSVL testing protocol, samples are to be collected only at the deepest part of the lake (the pit). More samples will be taken as summer progresses, and analysis/verdict will be available only at the end of the season. Enviro Lac Gauvreau is now fully supported by the “Réseau de surveillance volontaire des lacs” (RSVL).

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    RSVL is a provincial organization tasked with developing a picture of the health of lakes across the Province by helping members monitor parameters that affect the water quality and degree of aging of their lakes. The program measures levels of total phosphorous (TP), dissolved organic carbon (COD) and chlorophyll A (chl a). Following the RSVL protocol, our volunteers take water samples near the deepest part of the lake (the “pit”). This is done once a month in June, July and August. Transparency measurements are also taken, once every two weeks, using a Secchi disc. RSVL then arranges for pick-up of the samples, analysis and production of reports.
    science 2021 water quality test results
    Summary — 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.
    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.
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    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 Three Tests - "RSVL" Water Quality Sampling Protocol
    Three Tests using the "RSVL" Water Quality Sampling Protocol, 2021
    Protocol developed for the Réseau de surveillance volontaire des lacs (RSVL)
    July, 2021 — The three tests measure for:

    • Total phosphorus (TP), by nature the scarcest nutrient in lakes. TP is present in small amounts relative to the demand of algae and aquatic plants for growth. There is a direct relationship between phosphorus concentration, lake productivity, and trophic level. Eutrophic lakes, such as Lac Gauvreau, generally have a high phosphorus concentration;
    • Chlorophyll a (Chl a), a green pigment found in plants and algae. This parameter is thus an indicator of the biomass (quantity) of suspended microscopic algae in a lake water. Chlorophyll a concentration increases in relation to nutrient concentrations, especially phosphorus. There is therefore a relationship between chlorophyll a and the trophic level of a lake. Eutrophic lakes, such as Lac Gauvreau, are often subject to a significant production of algae;
    • Dissolved organic carbon (DOC), a general indicator of the amount of organic material dissolved in water as a result of the decomposition of plant or animal material. DOC concentration is used to evaluate the presence of humic substances causing the yellow or brownish colour of lake water. These humic substances are common in wetlands such as bogs, swamps and marshes. Water transparency, and hence Secchi disk readings, decrease with an increase in dissolved organic carbon concentration.
    Information obtained from these three parameters is completed by regular measuring of water transparency. Transparency diminishes with the increase in the quantity of algae in lake water. There is thus a relationship between water transparency of a lake and its trophic state. Eutrophic lakes, such as Lac Gauvreau, are generally characterized by low water transparency.

    > Read this full description of the Water Quality Sampling methods used by Lac Gauvreau volunteers (English PDF)
    science Archived E. Coli Tests
    science Archived Municipal tests
    science Archived H2O des Collines tests



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