HYDRO-ELECTRIC DAMS

Dam and Reservoir Creation
The damming of a river and the creation of a larger lake and flooded area in the reservoir causes a fundamental change to the environment in a larger surrounding area. These impacts range from loss or change of habitat to local climatic changes. Most of these impacts are contained in sections below, but some prime impacts from dam construction include:

Environmental Changes

• Loss of fish habitat as lakes change in size and depth and river flows change
• Loss of big game habitat as shoreline and shallow areas are impacted
• Loss of waterfowl habitat as marshes and wetlands are changed or eliminated
• Loss of fur bearing animals as habitats are changed and water flows vary
• Impediments to fish travel past dam and high current areas
• Impediments to animal travel due to new lakes and high water flow
• Local climate changes with potential for more fog, more humidity
• Release of methane and other green house gasses from decaying vegetation
• Downstream water may be over oxygenated, up stream water under oxygenated
• Changes in water temperatures and seasonal temperature changes

Impediments to Travel and Normal Life

• Logs and debris in the water endanger boats and motors
• Sudden changes in water depths and flows create danger
• Ice becomes unsafe in winter due to water level changes
• Dams make passage difficult, and create long portages
• Traditional portage trails are flooded or washed out
• Traditional camping sites are unsafe or flooded
• Docks and lakeside cabins and sheds are at risk from ice or flooding
• Shorelines are subject to slumping and erosion

Loss of Economic and Traditional Use Opportunities

• Turbines kill a lot of fish, especially large fish.
• Fish populations change in reservoirs due to environmental changes
• Fish populations change downstream due to habitat changes (Sturgeon)
• Fish populations suffer from loss of spawning habitat
• Waterfowl habitat is impaired or disappears
• Fur bearing animals are endangered and lose habitat (beaver and muskrat)
• Wild rice crops are in peril from changing water levels
• Travel and use of traditional resource locations is lost or impaired

Change in Seasonal Water Flows

Large dams often have high flows in winter (power demand for heating), low flows in spring (lower power demands and need to fill reservoir), high flows in summer (air conditioning power needs), and low flow in fall (reduced power and topping reservoir for winter). This reverses the normal water cycle of low flows in winter and high flows in spring and early summer, low flows in late summer, and increasing flows in fall and early winter before freeze up.

Fish and Fish Habitat are Damaged and Impaired

• Fish and other species depend on natural seasonal flows for life cycle.
• High flow in spring are necessary for spawning fish to travel and lay eggs
• Low flows expose eggs to drying or predation (esp. Sturgeon)
• Impacts life cycles of aquatic insects, which are food for fish
• Changes plant growth affecting hiding and resting habitat for fish

Big Game, Fur Bearers and Waterfowl are Also Affected

• Waterfowl habitat in swamps and marshes are affected by flow changes
• Waterfowl need stable water levels in spring and early summer to build nests and raise young and prevent predation
• Moose feed, rest and seek shelter in shallow water, and eat aquatic plants
• Animals can die or be injured crossing areas of unsafe ice or currents
• Animal migration patterns are disrupted by reservoirs and flow changes
• Fur bearers (mink, muskrat, beaver, otter, etc) are impacted by changing water level, especially in terms of winter denning success.

Flow Variation Interferes with Navigation and Winter Travel.

• Large water level changes above and below dam expose rocks, reefs.
• Lower flows below dam during summer may impair boat travel
• Open water below dam in winter prevents river crossing.
• Unsafe ice on reservoir in winter due to water level changes.
• Docks and storage sheds exposed to flooding and ice damage

Water Flow Peaking

Hydro-electric dams are easy to stop and start as the water is always ready to run the turbines. This is unlike coal or natural gas fired plants where starting and stopping boilers consumes fuel and takes time. So hydro-electric power is often used for "peaking" when loads are high for short periods of time.

Daily and Weekly Change in Flow

• Flows depend on power needs, not nature or northern community needs.
• Large flows during afternoon and evening for cooling, cooking supper, heating.
• Low or no flow during night when home use is less.
• Extra low flows on weekends due to more activities in the home.

Strongly Impacts Fish Habitat and Other Animals

• Water levels rise and fall in short periods of time not in a natural rhythm
• Stops some fish from spawning, especially in the spring and fall.
• Eggs and young fish are washed away, or dried out, and fish are trapped in pools.
• Kills insects and other fish food.
• Changes plant growth, affecting fish hiding and resting habitat
• Has impacts on wet lands and water fowl habitat for ducks, geese etc
• Wetland impacts affect large game animals like moose.

Impacts Navigation and Travel

• Danger of sudden flooding or surges below dams
• Changes in water level on lakes both upstream and downstream
• Debris from drowned trees and material swept off shore
• Impacts on travel between lakes and on portage trails
• Causes dangerous ice conditions in winter

Other Impacts

In addition to the dam and its immediate impacts, there are many other impact associated with hydro-electric power. These include:

• The power corridors that take the power out and connect to the electricity grid have their own impacts, which are not covered here.
• Roads that service the power plant or power corridor
• Spraying and vegetation removal and control under the power lines.

LEARN MORE:

Forest Threats & Solutions The impacts of human developments in the forest.

Hydro-electric Projects Threaten the Churchill River Learn about the Island Falls and Wintego Dams.