Myth:
Hydroelectric dams block the migration of anadromous fish and
are the cause of species declines
The hydropower
industry has taken extensive steps and spent hundreds of millions
of dollars to minimize the impact dams have on aquatic life.
The industry has been careful, where possible, to install systems
with proven capabilities to move fish both upstream and downstream
in all phases of their life cycle. Typically, turbines already
successfully pass between 85 and 95 percent of fish migrating
downstream on major rivers. This percentage can be further improved
using advanced turbine systems. Scientific applications of spillways,
fish screens and other collection and diversion techniques have
greatly improved downstream migration. For upstream passage,
lifts, bypass canals and ladders that simulate natural waterfalls
have proven to be successful.
But dams cannot
account for diminished runs prior to dam construction. Nor do
they explain why undeveloped rivers experience similar trends
in salmon counts as rivers with dams.
We will always
be frustrated with efforts to restore fish populations to the
rivers if societies efforts focus only on dams. There are a
multitude of factors that contribute to the ultimate failure
of species to return to their spawning grounds during their
life cycle. Often ignored are the harmful effects of: legal
and illegal harvesting that occurs both in-river and in the
ocean; hatcheries that cause disease to native species and increased
harvests; habitat degradation caused by mining, logging, agricultural
run-off, road construction and urban development; not to mention
the effect of climate conditions like, most recently, El Niņo
which warms the ocean currents and may disrupt fish migration
patterns.
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