Introduction
The health of Canada’s environment is intimately linked to
our vast network of rivers, lakes and wetlands. They provide critical habitat
and serve as travel routes for innumerable species of wildlife. It is immensely
important that the ecological integrity of aquatic ecosystems is maintained.
Unfortunately, aquatic ecosystems and their wildlife face
many threats in Canada. These include industrial, agricultural and residential
pollution, wetland destruction, and deforestation of adjacent and nearby
uplands. One of the most serious threats is posed by hydroelectric and other
types of dams that physically obstruct waterways, fragment or destroy aquatic
habitat, block fish migration, and alter water flow regimes. In some cases large
volumes of water are diverted from one watershed to another. Dams in Canada are
seldom constructed with fish passageways, effectively blocking fish from
travelling upstream to critical spawning sites. On the way downstream, hydro
turbines are a more source of injury and mortality. As a result many species
have been devastated, especially in southern Canada. Salmon have declined
drastically on both Canada’s east and west coasts and been extirpated from Lake
Ontario and its tributaries. The American Eel has been eliminated from much of
its historical range in Ontario. Lake Sturgeon have suffered steep declines
throughout much of their range.
Below we briefly discuss the effects of hydroelectric
development on the environment.
Hydroelectricity –
not green or clean
Hydroelectric development is often touted as a source of “green”
and “clean” energy by government and hydro developers. Unfortunately this is
not the case, as hydro has a major negative effect on aquatic ecosystems and wildlife,
and on water quality. This applies to both large and small developments. Large
developments typically have a large environmental footprint and can involve
ecosystem destruction at a massive scale. Small developments typically produce
only small amounts of power. Therefore, to produce a large amount of power
numerous sites must be developed, with cumulative impacts that can be severe.
Some of the negative effects of hydro development are listed
below.
Environmental effects of hydroelectric development
Loss of
most productive habitats by flooding of river valleys, lakes and wetlands
upstream of the dam and generating station. Reservoirs are typically created
to store water for hydro facilities. They may extend upriver from the
generating station or be located far upstream. They flood low lying areas such
as wetlands, the shorelines of lakes and river banks. These areas, which
typically have high biodiversity, are permanently lost and wildlife drown. In
some cases prime farmlands, which are often located in river valleys are
flooded and farmers or communities displaced.
Loss of
forest habitat at greater elevations. Reservoirs often flood substantial
areas of forested lands well away from the river itself.
Interruption
of a river’s natural flow cycle. Aquatic wildlife and vegetation are
adapted to and often rely on the natural flow of a river and its seasonal
variation. Hydro development disrupts that pattern both in the reservoir(s)
above a dam and in the river below the dam.
Changes in
water temperature. Changes in water temperature due to hydro development can
have significant negative effects on some species.
Damage or
destruction of delta/estuary habitats far downstream of the generating station.
Deltas and estuaries are among the most productive habitats on earth. The
health of these ecosystems and their wildlife rely on natural seasonal flooding
regimes and on sediments transported by the river. Hydro facilities, often far
up the river can have devastating effects by eliminating the natural flooding
cycle, and decreasing sediments. The Peace River delta, one of the continent’s
most significant wetlands, has been severely damaged by the construction of two
upstream hydro facilities.
Sedimentation.
Sediments that normally are flushed downstream are deposited in slow moving
waters of hydro reservoirs. They no longer provide nutrients downstream. The
sediment build-up behind the dam can cause nutrient loading and a decrease in
oxygen.
Effects of
peaking operations. In peaking operations water is released from the
reservoir above the dam when demand for electricity is high, but held back when
demand is low such as at night or on weekends. Thus the water flow can change
dramatically over a short period of time and have significant negative effects
downstream. In particular, the release of large quantities water can cause severe damage to downstream
riverbanks and their habitat. In addition fluctuations in reservoir water levels
can render the shorelines of the reservoir unstable.
Damage or destruction of ecological links.
Rivers form important ecological links between natural areas which may be
damaged or severed by hydro development.
Fragmentation of a river’s ecosystem and the blocking of fish
migration routes. Dams act as a physical barrier that fragments a river’s
ecosystem and isolates aquatic species that live upstream or downstream. In
particular, hydro dams usually disrupt or eliminate fish migration. Fish
ladders are almost never installed. Therefore fish are unable to move upstream
past the dam. On the way downstream fish are killed and maimed in the turbines.
This has had drastic effects on many fish populations across Canada.
Dewatering sections of the river. In some instances a large
portion of a river’s flow is diverted via a pipe or channel to the generating
station and then back to the river. In extreme cases this can leave a section
of the riverbed essentially dry. In other cases a river may actually be
diverted into another watershed to feed generating stations there. This has
occurred for example in northern Manitoba where the Churchill River has been
diverted into the Nelson River.
Greenhouse gas emissions. Decaying vegetation in hydro reservoirs causes the release of the greenhouse gases methane and carbon dioxide. Flooded peatlands are thought to be the largest emitters associated with reservoirs in the boreal forest region. Flooded peatlands and forests no longer sequester carbon. In addition, substantial greenhouse emissions are associated with the production of the materials for the dam and with the operation of machinery during construction.
Mercury pollution. Bacteria in reservoirs convert inorganic
mercury in flooded soils to methyl mercury which is then concentrated up the
food chain. Mercury is a strong neurotoxin and when contaminated fish are
consumed by humans they can suffer very serious health effects. High levels of
mercury have been reported in fish from many Canadian hydro reservoirs and have
resulted in bans or restrictions on the human consumption of fish.
Power corridors and access roads fragment wilderness and natural
habitat. Power corridors and access roads may extend for long distances
through what were previously wilderness areas depending on the remoteness of the location of
the generating station.
Service roads allow access for poachers and other illegitimate users.
Service roads and power corridors act as conduits for invasive species. Invasive species pose a threat to many ecosystems across the country.
Interbasin water transfers associated with some hydro developments can
permit the movement of invasive species from one basin to another.
Cumulative effects of multiple hydro projects in a single watershed.
Environmental Assessments seldom consider the cumulative effects of the various
existing or proposed hydro projects on the river, nor the effects of dams
constructed for other purposes. The cumulative effects of several smaller dams
can often equal that of a single large dam.
Other effects of hydro development
Hydro development has other major
drawbacks that are not necessarily of an environmental nature.
Damage to recreational resources and ecotourism. Many recreational
and scenic resources, such as canoe routes, scenic waterfalls and rapids occur
along rivers and can be lost due to hydro development. This has a direct
negative impact on ecotourism.
Destruction of historical, archeological and cultural sites.
Typically historical, archaeological and cultural sites are clustered along
river banks and lake shores, as these were the places that First Nations and
European settlers chose for their settlements and camps. Rivers formed the main
transportation routes across much of the country prior to 1900, and in the north until the mid 1900's. Portages around waterfalls and rapids are
particularly rich sites. Unfortunately they are also the sites of hydro
generating stations and associated infrastructure. Many important sites have
been permanently lost due to hydro development. Many more are threatened.
Safety concerns. Hydro dams are a safety hazard for downstream
users such as boaters and swimmers, because of the large fluctuations and flows
that occur downstream. In addition, catastrophic dam failures due to
earthquakes or aging facilities can cause substantial damage and loss of life.
Example of hydroelectric proposals
An example of the hydro projects that
threaten Canada’s rivers, aquatic ecosystems and wildlife is outlined below.
Peace River Site C
hydroelectric project, northeastern British Columbia
Site C, a mega hydroelectric project is under construction on the Peace River in northeastern British Columbia. The dam will create a reservoir stretching more than a hundred kilometres (LINK) along
the river and its tributaries. It will flood critical wildlife habitat, prime
farmland, and historical and First Nations cultural sites. It will likely have
detrimental effects on the Peace River delta, a United Nations World Heritage
Site downstream.
Wildlife habitat:
The section of the Peace to be flooded forms a critical ecological link in the
south to north Yellowstone to Yukon (Y2Y) Conservation Initiative. Hydro development threatens to sever this
link for species such as the grizzly bear. The Peace River Valley provides the
only breach in the Rocky Mountains and hence is an important east-west corridor
for wildlife. Wildlife have already been drastically affected by development
along the Peace, especially by the WAC Bennett dam and its huge reservoir which
were constructed farther upstream in the 1960’s.
Peace River delta:
The Peace River delta is a huge freshwater delta located downstream in Alberta
where the Peace River meets the Athabasca-Slave River system at the west end of
Lake Athabasca. It is of international importance and has been designated a
United Nations World Heritage Site. The wetlands of the delta have already been
significantly affected by the WAC Bennett dam because of alteration of the
river’s natural flow regime. No environmental assessment was carried out when that
dam was constructed in the 60’s. It is unclear how serious the effects of the
new proposed project will be for the delta as the necessary environmental
studies have not been conducted.
Farmland: Only a
tiny fraction of British Columbia is suitable for agriculture. Much of the
Province’s food is imported. One would have thought that the protection of the
Province’s prime farm land would be a top priority. Think again! The portion of
the Peace River Valley that will be lost due to flooding by the Site C dam
includes a large area of class 1 and class 2 farmland, which is considered the
best in northeastern BC.
Despite the approval of the project by both the federal and provincial governments, fierce opposition has continued on the part of environmentalists, First nations and farmers. Local First Nations filed a law suit to
stop the project due to the devastating effects which it would have on their
traditional lands. Alberta First Nations filed a separate lawsuit claiming that
the downstream effects of the project on the Peace River Delta have not be
properly considered. Heritage Canada National Trust designated the Peace River as one of Canada's 10 Most Endangered Places because the Site C project will destroy many First Nations traditional and sacred sites, other historical sites, wildlife habitat and prime farmland.
The site C project, which was first developed nearly half a
century ago, and has been rejected in the past, should be halted once again.
For more information:
Stop Site C
Wilderness Committee (includes a map of the
portion of the Peace River that is affected)
Peace Valley Environmental Association
Report on Peace River Valley natural and cultural values
Y2Y Conservation Initiative
Its Our Valley
For information on rivers at risk in Ontario:
Ontario Rivers Alliance
For information on the many negative environmental effects of hydroelectric development, both large and small:
Ontario Rivers Alliance, Hydro Impacts 101 Report
Moses-Saunders hydro dam, St. Lawrence River, Ontario