Aquatic Environments: Lakes, Rivers and Streams

Many aquatic environments have been channelized or even filled in to make way for urban and municipal development. They are now protected by numerous laws and regulations at every level of government.

What is an aquatic environment?

Aquatic environments include watercourses (streams, rivers, large rivers, etc.) and bodies of water (mainly lakes). They may be natural or man-made. They are covered with water most of the time, and their flow is either permanent or intermittent.

The St. Lawrence River, the Gulf of St. Lawrence and the seas surrounding Quebec are protected under the Environment Quality Act, like all other aquatic environments in Quebec.

Ditches along public or private roads, drainage ditches and boundary ditches do not benefit from the same protection as aquatic environments, unless they contain fish or are an extension of a stream.

The two types of aquatic environments

Watercourses

Watercourses have a source and a confluence or a mouth. They are generally linear. Streams, rivers and large rivers are all watercourses.

They serve as corridors for fish and for the migration of other aquatic species.

Bodies of water

Bodies of water include lakes, inland seas and oceans. They may be natural or man-made. They form in depressions in the ground, in excavated basins or at the bottom of valleys that have been blocked by a dam or dike. Bodies of water receive all the water from the higher ground of their watershed, either directly or through a network of tributaries. They are permanently covered with water.

For our purposes, ponds, marshes and swamps are considered wetlands rather than aquatic environments.

Aquatic environments commonly found in Quebec

• Stream
• River
• Large river
• Lake

Stream

Streams are shallow watercourses. Their bed is usually 1 to 5 m wide. They may be fed by a spring and flow into another stream or a river. They have a very low flow (less than 2 m³/s), but the direction of the current is easy to determine. It is not unusual for a stream to dry up during dry periods.

River

Rivers are watercourses that flow into a large river, a lake or another river; they are tributaries. The Magog River flows into the Saint-François River. The Saint-François River, in turn, flows into the St. Lawrence River, as do the Richelieu and Ottawa rivers.

Although rivers vary in width, the direction of the current is always easy to determine.

Large river

Large rivers (fleuves in French) are major watercourses with wide beds and high flows. They are formed by one or more rivers and flow either into another large river or into an ocean. For example, the St. Lawrence River flows into the Atlantic Ocean, and the Fraser River flows into the Pacific Ocean.

A large river can flow for more than 500 km, and its watershed can cover an area of more than 100,000 km².

Lake

Lakes are bodies of open water permanently covered with fresh water. They are wide, generally round in shape and usually more than 2 m deep. Because of their low flow, it is often difficult to determine the direction of the current. They may be artificial or natural.

Lake Ontario, Lac Saint-Pierre and Lac Saint-Jean are examples of lakes well known to Quebecers.

Aquatic environment terminology

Bank or shore

Banks (or shores) are the land areas along the edge of a watercourse or body of water that flood easily.

High-water mark

The high-water mark is an imaginary line marking the transition between the aquatic and terrestrial environments. It is generally the level the water reaches each year. Its position can be determined using a botanical method, by observing the plants present: the high-water mark lies where terrestrial plants take over from aquatic plants.

Littoral zone

The littoral zone extends from the centre of a watercourse or body of water to the high-water mark.

Riparian buffer

Riparian buffers are the strips of land on each side of an aquatic environment, extending from the high-water mark to 10 m for banks with a slope of less than 30%, and to 15 m for banks with a slope of more than 30%.

Work in the riparian buffers and littoral zone of an aquatic environment is strictly regulated.

Floodplain

Floodplains (or flood zones) are flat or gently sloping areas located near a watercourse or body of water. They are covered with water only during floods, and are therefore subject to occasional or periodic flooding. Floodplains are categorized as high-velocity zones when they are flooded by 20-year floods, and low-velocity zones for 100-year floods.

References

• Vos lacs et cours d’eau : des richesses collectives à protéger
• Ministère de l’Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs
• Protocole de caractérisation de la bande riveraine
• Government of Quebec 
• CRE Laurentides