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What are people doing to improve the impact of dams?
Seattle City Light (#) is
voluntarily raising river flows downstream of the Ross Dam on Skagit Rive to
save salmon nests downstream. Read more in the Dam News!
Lower
Snake River (#) dams have done the same, helping spring migration of
endangered fish like chum and steelhead, species of salmon.
In Washington state, new fish ladders are in the works for several
dams. A fish ladder picks the fish up on one side of the dam,
carries them up and over the dam in an elevator and deposits them on the
other side. Read more in the Dam News!
Five small dams in California will be decommissioned, flows will be
increased, fish ladders will be enlarged, and screens will be placed on
turbines to help runs of winter, spring, fall, and late-fall chinook and
steelhead on Battle Creek. Fish often must pass through turbines (which make
electricity) to pass a dam. The fish are disoriented when they emerge and
cannot continue on their journey.
The Flat Rock Dam in Philadelpha County, PA (#) will soon have new fish
ladders to help shad, striped bass, and other fish travel up the Schuylkill
River. The dam, a 21 ft-high concrete gravity dam, was built in 1977 for
recreation purposes. A budget of $21.8 million has been allocated for
the project, which is estimated to bring in $2.5 million in
fishing trip revenues once it's complete.
PR Newswire:
PA Dept of Envr Protection press release, 6/11/99
Two dams are going down near Portland, Oregon: Marmot Dam (Marmont in the
National Inventory
of Dams (#)) on the Sandy River and Little Sandy Dam on the Little Sandy
River. The Marmot is 87 years old
and 40 feet high and supplied water and hydroelectric power (type other). The
breach (*) of these dams will allow for passage of salmon and steelhead,
prompted by the listing of theses fish as threatened species. The project cost
projection is $10 million and should take 2 years. It is reported that the
structures will actually be removed.
The Savage Rapids dam, near Grants Pass, Oregon is a concrete
multiple-arch buttress dam built in 1921 forirrigation; officials would like
it removed to improve fish runs. But a bill has passed in the Oregon Senate
which would give the legislature the power to veto a dam removal
in Oregon. Removal has not passed yet.
States News Service: Salem, Oregon headline, 5/5/99
The fish at Bonneville (#) Dam just can't
win. A huge pipeline was built to transport the fish around the dam, but the
pipe is open and makes the fish extremely susceptible to seagulls out for
dinner. A screen for the pipe is in the plans.
The Bonneville Power Administration (#) is
offering money for fish -- an effort to improve the salmon population in the
Columbia and Snake Rivers
(#). Northern pikeminnow are huge predators of young salmon; each northern
pikeminnow greater than 11 inches in length caught and brought in to a
registration will get you $4 - $6. The BPA feels that millions of young
salmon have survived as a result.
American shad have begun their migration from the Chesapeake Bay up the
Susquehanna River to centeral Pennsylvania with the help of fish
ladders on the Conowingo
Dam (#) in Maryland. The fish have two choices: the west
lift, from which they will be shipped upriver by truck and returned to the
river near Harrisburg, Pa; or the east lift, from which they
will be released into a manmade flume to swim upriver themselves. Tours are
available.
PR Newswire: PECO Energy Company press release,
4/26/99
The US Bureau of Reclamation (#) is
trying to help some fish that have been hurt by the Glen Canyon Dam. The
humpback chub have been endangered since 1967 because of the
temperature drop in the Colorado river when the dam was built.
The Bureau has suggested a plan to warm the water by taking it from the top of
the lake; this might improve the fishes' chance of survival.
Their plan is waiting for approval.
Associated Press Heaadline, 1/27/99
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What's your opinion on the societal impact of dams? |
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Authorities, politicians, and engineers have to take both the advantages and
disadvantages into account when planning a dam
or considering its decommission. If a dam is being built, they also have to consider what type of dam
should be built. The design of the dam, the size
and shape, must also be considered, and is usually dealt with by the Civil Engineers.
The best type of dam varies from site to site. |
What are four of the different
types of dams?
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