Impacts of river and lake regulation

Regulation changes the natural flow rate or water level of a lake or river. What impacts does this have?

The water level in regulated lakes and rivers usually varies less than it would do naturally. Spring floods are less severe, and in periods of drought, the water level does not drop as low as it would without regulation. A less variable water level benefits farmers and shoreline residents.

While some animals breeding close to the shore may also benefit from the fact that their nests are not flooded, regulation means that flood meadows and their unique species are lost.

When the hydrological conditions of a river are modified, many other things also change, such as the way sediments are carried by the flow and deposited. This may have a major impact on the living conditions of animals in and along a river.

The greatest concrete change is brought about by dams, which alter the channel of a river and prevent migratory fish from swimming upstream to their spawning grounds. Special fish passes are built in an effort to mitigate this adverse impact, and in recent years their designs have been improved, making it easier for fish to find their way upstream past a dam.

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