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The Problem with Phosphates

The presence of phosphorous results in excess nutrients that promote the growth of algae — including blue-green algae blooms — and the propagation of Eurasian watermilfoil. Annual water quality assessments, including phosphorous sampling, are a useful part of a milfoil and blue-green algae monitoring program. This is especially true for a relatively small body of water like Lac Gauvreau that is bordered by agricultural land on the west side and that is subject to rainwater runoff from an expanding residential development on the east side.

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Phosphate levels concerning

Biologists assess Lac Gauvreau, finding high nutrient levels

High nutrient levels tied to growth of blue-green algae and Eurasian watermilfoil.

April 9, 2022 —Based on onsite observations and scientific evaluations, the non-profit environmental organization ABV des 7, has released a summative report on the condition of Lac Gauvreau and its shoreline. The report was commissioned by the Enviro Lac Gauvreau owners association.

In a Zoom webinar presented on April 9, 2022, biologist Jean-François Ouellet, M. Env., who is the General Manager of ABV des 7, gave assurance that much can be done to preserve and restore lake health. In presenting the organization's report, his prime recommendation was the preservation and restoration of the lake's riparian (shoreline) buffer.

> Visit our "Restore Your Shoreline" page for details, including slideshow and video presentations

2021 water quality tests results released in 2022

The Enviro Lac Gauvreau Association has released the final results and interpretations of water quality tests that were conducted during the summer of 2021. That data is now available on our "Water Quality Monitoring" webpage. Phosphorus levels remain as high as indicated in previous tests.

The last set of official water quality tests done by the Municipality in 2014 yielded phosphorous levels ranging as high as 0.038 mg/L for Parent Creek which flows into Lac Gauvreau. The readings were troubling, as Parent Creek water clarity was classified as Eutrophic — very bad — meaning that there was very low water clarity (turbidity) with high levels of phosphorous, algae and nutrients. The 2014 Municipal water quality tests also included phosphorous readings for Lac Gauvreau that ranged from 0.012 to a reading of 0.046 mg/L at Alphonsus Bay on the north-east end of the lake. An average of the four locations tested produced an overall water clarity classification of Mesotrophic, indicating moderately clear water with moderate levels of phosphorous, algae and nutrients. (Source) This status has since been downgraded to Eutrophic.

What does this mean for Lac Gauvreau?

The most important information about a lake’s health is gained by observing trends in the annual averages of test results over several years. There is no telling what test results would indicate now, however, but there are some clues. For example, by the end of summer the lake water begins to take on an odd green tinge. As fall progresses, that tint turns into a deep emerald green colour. Also, by mid-fall, a blue-green-yellow slick appears on the shoreline every morning (see photos below taken in mid October, 2019). The presence of pollen has been ruled out. These two occurrences may result from a buildup of algae in the water after a hot, nutrient-rich summer.

Click on images to enlarge

Eurasian watermilfoil in green-tinged
water (Lac Gauvreau, fall 2019)

Painted shoreline (Lac Gauvreau, fall 2019)

Lac Gauvreau Still At Risk!

Reported blue-green algae blooms have appeared in 2000, 2008 and as recently as late summer 2020 and spring of 2021, and Eurasian watermilfoil beds continue to grow in a pervasive manner throughout many parts of lac Gauvreau.

Background

According to the Lac Gauvreau News - August 2010, Published by the Gauvreau Lake Environmental Protection Association, “Phosphate levels in the Lake remain elevated, a state which continues to foster the possibility of the appearance of algae.”

The Lac Gauvreau News - June 2009, wrote this warning: “Lac Gauvreau Still At Risk!... The appearance of an algal bloom (cyanobacteria or blue-green algae) early last November confirms that our lake remains vulnerable to this kind of pollution [caused by nutrients such as phosphorous].”

High nutrient and algae levels have been of great concern for years. This story in The Low Down to Hull and Back News, June 18 - 24, 2008 reminded readers of this fact: “The health of the lake [Gauvreau] was called into question in 2000, when a blue-green algae bloom devastated cottagers by causing the closure of the lake… After 2000, with the help of the mayor, the lake’s volunteer environmental group put together an action plan to clean up the lake…”

Blue-green algae: Lac Gauvreau a model to follow
La Pêche, 27 August 2007 — Messrs Robert Bussière, Mayor of the Municipality of La Pêche, and John Leech, President of the Gauvreau Lake Environmental Protection Association were pleased to welcome Mme Line Beauchamp, Minister of Sustainable Development, the Environment and Parks, on the occasion of her visit to the Outaouais, part of a provincial fact-finding tour on the problem of blue-green algae. The visit is public recognition of the positive results of concerted efforts over seven years to significantly reduce blue-green algae and the public health threat presented by the production of cyanobacteria.

Proactive from the start of the crisis in August 2000, the Municipality has put in place several programs in collaboration with the Association.
>Read the joint press release in full

Revitalization project of Parent Creek

Characterization and revitalisation project of Parent Creek
Aware of the necessity of action for the protection of the water resource and aquatic habitats, the Gauvreau Lake Environmental Protection Association (GLEPA) decided to establish a drainage basin enhancement plan, starting with its main affluent.

The dredging of the Parent creek in the 1960s resulted in the disappearance of habitat diversity. The Association thought that it was possible to implement corrective measures to revitalize the creek, increasing the quality of fish habitats and their productivity. The aquatic habitats of the creek were not known at the time. Acquiring this knowledge was an essential first step in establishing priorities for its revitalization.

The following were the specific objectives of the project:

Characterize the aquatic habitats of Parent and Gibson Creeks (18 Km),
Characterize the conditions of the creeks shorelines and erosive areas,
Establish a five-year plan for the revitalization of aquatic ecosystems.

Several studies had already established the Parent Creek as the main source of nutrients, such as phosphorus and nitrogen, which favour the anarchic growth of plants, algae and cyanobacteria in the lake. The expected by-product of the creek revitalization project was the substantial reduction of nutrients inflow to the lake and the slowing of its aging process.

The GLEPA mandated a private consultant’s firm to conduct the characterization of the Parent creek. Read more and see the report below.

Due to a GLEPA initiative, the environmental consulting firm PRO FAUNE published a ‘Development Plan for the Aquatic Habitats and the Banks of Parent Creek’. This study report identified a number of concerns that affect the quality of the aquatic habitats of the creek – and as a consequence, the water quality of Lac Gauvreau – including the condition of the creek banks along the farm fields, the electric fencing, and the access by cattle for drinking water.

Information already available was combined with data collected on the ground in September 2007, allowing an evaluation of the problems of Parent Creek and the formulation of recommendations for the development of the potential for fauna and of water quality. With this information, the Association and its local and governmental partners were able to compose a plan for intervention and protection of the sensitive habitats for fauna and the creek banks in order to preserve the biodiversity of the principal inflow to Lac Gauvreau.

In summary, to improve the quality of the Parent Creek ecosystem and to optimize its potential for fauna, the report deemed it essential to keep livestock at a distance from the Creek, to establish adequate watering sites, to stabilize the creek bed and banks, and to ensure the effectiveness of individual septic systems of residences in the drainage basin in order to reduce the runoff of suspended material, total phosphorus and fecal coliform. Read the Parent Creek revitalization study; key findings published June 28, 2008. Read the Executive Summary Parent Report.

> Read article in Gauvreau Lake News, June, 2008

In 2007, Lac Gauvreau received $14,000 to study the impact of pollutants flowing into Lac Gauvreau from Parent Creek. According to The Low Down to Hull and Back News August 29 - September 4, 2007, “…The aim of the study… is to… pinpoint the sources of any deterioration [of Parent Creek], such as high levels of nutrients. High levels of nutrients, like phosphates, can lead to higher chances of algae bloom…” [and of promoting the growth of Eurasian water-milfoil].

> Read Association press release

Eutrophication - The death of a lake

Eutrophication is a singular but natural form of pollution of certain water ecosystems which occurs when a lake receives too much nutritive substrances assimilible by algae, causing those to proliferate. The principal nutrients at the origin of this phenomenon are phosphorus and nitrogen.

A lake receives, naturally and continuously, quantities of nutrients brought by streams and surface waters. Stimulated by this substantial contribution, certain algae grow and multiply excessively. This growth occurs particularly in the surface layers of a lake because plants need light to develop. It is then said that the lake is aging. Such a situation, when it occurs, still worsens when the temperature is high because the concentration of oxygen in water decreases inversely to temperature.

This natural process is very slow: it can spread out over centuries or millenia, and sometimes over longer periods. But eutrophication can be strongly accelerated by the contribution of domestic, industrial and/or agricultural effluents and lead to the death of aquatic ecosystems in a few decades and even in few years. This phenomenon is also known as hypereutrophication or dystrophication.

>Read more on Wikipedia

Reduce phosphate in our lake

What you can do to reduce phosphates?

Do not run outdoor shower outflow directly onto the ground or directly into the lake, regardless of the type of soaps and personal care products you use. Place outdoor showers in sensible locations that are far from the shoreline and that have no impact on the quality of the lake water.
Be sure that the cleaning products and detergents that you use are phosphorus-free. This includes dish and laundry detergents, as well as personal care products.
Follow maintenance guidelines for your septic system.
Phosphorus sticks to soil particles, so ensure that your property is well-vegetated and no soil or nutrients are washed into your lake.
Plant shrubs, trees, and grasses downhill from your septic system to act as a sponge (they will tie up excess nutrients and water, as well as prevent soil erosion).
Develop and maintain vegetative buffer strips along lake shorelines, stream and river banks to slow down run-off, capture sediments and increase infiltration and phosphorus uptake rates.

Phosphorus pollution from agricultural runoff can seriously impact water quality. In addition to the above best-practices, the following are good reminders to local agricultural property owners in the Lac Gauvreau watershed.

Know your soil and manure phosphorus levels through testing and analysis. Match fertilizer and manure phosphorus to crop needs.
Do not over-apply fertilizer or manure phosphorus on sites adjacent to rivers, streams, creeks, reservoirs or lakes
Manipulate animal and poultry diets to reduce the amount of phosphorus excreted in manure.
Apply manure based on crop nutrient requirements, using methods that reduce the risk of runoff to surface waters.
Maintain effective soil erosion control practices on application sites including no-till agriculture, contour tillage, leaving crop residues on the soil surface after harvest and growing winter cover crops.