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Acerca of

lac Brome


Phosphorus (P) is the determining element for the proliferation of cyanobacteria. To avoid water degradation, it is essential to reduce its intake.

But nature does things well. Phosphorus is an element present in nature in very limited quantities. Its contribution is essential to the growth of living organisms, just like nitrogen (N) and potassium (K).

Unfortunately, human activity disrupts the natural phosphorus cycle with the result that too much phosphorus ends up in water bodies, altering the natural balance and causing biomass (aquatic plants, cyanobacteria, etc.) is abnormally stimulated (we often speak of a ratio of 1 to 500, that is to say that 1 kg of phosphorus can lead to the production of 500 kg of biomass). We will say that the lake is too productive and that its aging is accelerated (eutrophication).

Image by Antoine Rault

The main
sources of phosphorus contaminating
streams and lakes

Phosphorus can be particulate or soluble (dissolved). Most of the time (70% to 90%), it is particulate and attaches itself to fine soil particles, which are carried by water runoff towards watercourses.  The sources of phosphorus production are numerous and most of the time anthropogenic (by man).

origine phosphore
cycle du phosphore

The main sources of phosphorus inputs
to the lake


Sediment already present in the lake contains large amounts of phosphorus, a result of past carelessness. This phosphorus, under certain conditions, can be released into the water column and become available again for plants and algae. 


This important source in Brome Lake could eventually be reduced if the inflows from the watershed are radically reduced and if the lake manages to "take back the upper hand" (through the process of water renewal, which we know takes 10 months to Lac Brome and by the evacuation at the outlet).  CLB's strategic target is to reduce the phosphorus input into the lake by 50% over 5 years, i.e. 10% per year. 


Fertilizers for aesthetic purposes, PROHIBITED! All municipalities in the watershed must ensure that the spreading of any fertilizer is prohibited on the lawns. Ville de Lac-Brome has already adopted such a measure in 2010. In 2011, golf courses in the municipality will be subject to the same by-law.

Sources of phosphorus, article by Peter F. Wade

Comparative table of phosphorus concentrations 
for major dishwasher soap brands


Surface water management: difficult to walk the talk!

We agree on the need to better manage surface water, in particular, because of the erosion and damage to public and private infrastructures caused by water surges, it is clear that concrete initiatives require a lot of consultation. and political courage.

CLB is particularly disappointed with the timidity of the measures proposed in terms of riparian strips and the protection of mountain peaks. On the other hand, certain initiatives deserve to be commended, in particular the protection of the wooded cover and the measures to promote the infiltration of water on the land.

Let's hope that the MRC and the mayors will be able to take the bold measures that are necessary and will make the MRC a leader in the field of runoff management, an essential factor in the quality of the water in our lakes and rivers. Other MRCs have done so.

La santé du lac
The health of Brome Lake is a concern for many citizens
due to the increased presence of cyanobacteria. 
Image by Niklas Hamann

The salt accumulates
in fresh water

The tons of salt spread on the roads of Quebec this winter have not disappeared. As the snow melted, much of it ended up in freshwater lakes and rivers. 

Image by Jordan Whitfield

The salt accumulates
in fresh water

The tons of salt spread on the roads of Quebec this winter have not disappeared. As the snow melted, much of it ended up in freshwater lakes and rivers. 

The first
success factor

The first factor of success is certainly the management of runoff water, in particular when laying out street ditches, drainage ditches, dirt roads, bare soil (during construction of all kinds). Countering soil erosion is a top priority that can be easily accomplished.


Erosion and sedimentation

Erosion is the action exerted by wind, water or ice that moves soil particles. The sensitivity of a soil to erosion depends on the climate, the relief, the presence of vegetation and the nature of the material.

The health of a lake is the result of the health of its watershed. The quality of the water is therefore not only the concern of the residents of the lake but of all those who live near a watercourse (ditch, stream, etc.) which flows into the lake. .

Our worst enemy is phosphorus. Every year, the tributaries pour far too much phosphorus into the lake, particularly in the spring. Phosphorus is carried by sediments present in runoff water. Phosphorus inputs from tributaries are high and accumulate at the bottom of the lake every year! This is approximately the equivalent of 100 truckloads of sediment flowing into the lake, thus contributing to its premature aging (eutrophication).

Installations septiques

Septic systems near watercourses

are a real potential for contamination.


Septic systems

The territory of
the town of Brome-Lake


Septic systems




Septic systems



at Brome Lake
and its watershed

Harmful to the environment






Should the deployment of new techniques for disposing of slurry be accentuated, provided that the capacity of each catchment area is respected in terms of animal units?


In terms of riparian strips, there are solutions that allow spectacular returns. For example, the hybrid poplar is a real phosphorus pump, it grows extremely quickly and can be harvested after a few years. On the other hand, as long as this type of development involving an extended riparian strip will compete with subsidized crops, in particular the cultivation of corn, which we know is very harmful to waterways, it is very unlikely that we will progress towards strips residents worthy of the name!

The agricultural environment can contribute to the sanitation of our bodies of water. Farmers are bombarded with all sorts of new government requirements. They are pragmatic people who, for the most part, would like nothing better than to implement good environmental practices on their land. In our region, some farmers are involved in the Prime-Vert program. However, it is going too slowly. It would be a win for everyone if the bureaucratic requirements were simplified and if the multiple government agencies (MAPAQ, MDDEP, Fisheries and Oceans, Natural and Wildlife Resources, MRC) were better coordinated.

Sequester CO2
protecting waterways

The Arbre-Évolution cooperative offers a turnkey service to farmers who want to use their riparian strips to sequester carbon… and profit from it.

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