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Ancre 1

Brome Lake: the city’s
economic heart

It is essential to remember that the quality of the social fabric and the economic level of Lac-Brome is directly proportional to the quality of the lake water and its safe uses; the two components are intrinsically linked.

An unusable lake means, among other things, a drop in the property value of residences, loss of income for the municipality, drop in tourist attraction, the number of second homes, reduction in tourism and business customers.

Brome Lake

Issued : May 16, 2024

Water transparency

SECCHI depth

Water temperature

Risk of cyanobacteria bloom

Water level

Water flow at outlet


5,8 m of visibility

15,6 °C

Very low

197 m

5,00 m³/sec

Condition du lac

Conditions générales du lac

The life of a lake on a geological scale is relatively short.  Like human life, from birth, the lake ages, the walls of its basin are slowly covered with sediments from the tributaries, or organic matter that decomposes at the bottom.  Slowly the lake changes, it becomes shallower, there is more siltation, aquatic plants, until the day when the lake looks more like a marsh than a body of water proper.  All these changes modify the trophic level of the lake, which means: the level of biological production and the physicochemical composition of the water.

Niveaux trophiques des lacs

CLB measures throughout the summer the different parameters that give an indication of the trophic level of the lake.  The following table shows what levels the lake is at in 2021 according to each indicator.

Niveau trophique lac Brome 2023_RSVL.png

The mesotrophic lake

The lake is considered mesotrophic, so the lake is productive, this productivity is characterized by an increase in algae and aquatic plants. The change from an oligotrophic lake to a eutrophic lake naturally operates over a long time scale, but human activities can cause these changes to accelerate rapidly.

Qualité de l'eau

Abundant phosphorus and nitrogen are the main cause of this degradation.

These essential nutrients for plants, when present in excess, create an imbalance that increases the productivity of the lake.  So more food, more plants and fish, but also eventually, a lack of oxygen for aerobic living beings, such as fish. The level of chlorophyll is high, which shows an environment with a very high biomass of microscopic algae in suspension. This variable places the trophic state of the lake in the eutrophic class.

As for the average concentration of dissolved organic carbon, it is 3.4 mg/l, which indicates that the water is slightly colored.  The color therefore has a small effect on the transparency of the water. The loss of water transparency is therefore attributable to the algae present in the water column.

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