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Fox River Ecosystem Partnership
Statement Regarding Dams
It is
said that there are enough dams in the U.S. for one to have been built every
day since the nation began in 1776. Dams generally were built to store and
provide water for mechanical power generation, industrial cooling,
hydroelectric power generation, agricultural irrigation, human consumption,
and impoundment-based recreation. They also have been used for flood
control and maintaining channel depths for barge transportation.
Although beneficial for various uses, dams also have negative impacts that
may include increased risk of drowning; degraded aquatic habitat, water
quality, and fish communities; blocked fish spawning migrations; and
impaired flowing-water recreation (canoeing and kayaking). In many places
around the country, dams are being removed or modified rather than repaired
or reconstructed in an effort to restore naturally flowing river systems.
The Fox River Ecosystem Partnership (FREP) has identified in
its Integrated Management Plan for the Fox River In Illinois (1999)
dam removal or modification as an important watershed-based approach to
enhance and restore aquatic habitat and fisheries in the Fox River basin.
Current, ongoing studies evaluating the effects of dams on various
ecological parameters in the Fox River, including water quality, and fish
and invertebrate populations, and fisheries habitat suggest that dams are
having substantial negative impacts on the ecology of the watershed.
Fox River Ecosystem Partnership is fully aware that many
factors need to be considered when addressing any dam removal or
modification alternatives. However, from a strict ecological standpoint, we
believe that dam removal is the soundest alternative.
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Article from FREP's Fox River News Winter 2002
Fox River Fish Passage Feasibility Study
By Victor J. Santucci, Jr.,
Research Biologist, Max McGraw Wildlife Foundation, Dundee, Illinois
There are 15 mainstem dams and numerous
tributary dams in the Illinois portion of the Fox River watershed. Many of
these dams were originally built in the 1800’s to provide mechanical power
for grist or lumber mills, but today serve little function except to
maintain flat-water pools/impoundments upstream of the dams. The Max McGraw
Wildlife Foundation has recently completed a two-year study to determine the
effects of dams on fisheries, macroinvertebrates, physical habitat, and
water quality in a 100-mile stretch of the Fox River between the Chain of
Lakes and Dayton, Illinois. In addition, fish passage options were
identified for each of the 15 mainstem dams. Options included complete dam
removal and river restoration or retrofitting dams with ramps, fishways, or
bypass channels to provide fish and/or canoe passage. Cooperators on this
project include the USEPA, the Illinois Department of Natural Resources, and
Steve Gephard, a Fish Passage Specialist from Connecticut.
Sampling for the study took place during summer low-flow
conditions at 40 sites located in free-flowing river areas directly below
dams, impounded river directly above dams, and free-flowing or impounded
mid-segment areas between dams. Results convincingly showed that dams are
having a detrimental effect on the Fox River by reducing biodiversity of
fishes and altering macroinvertebrate communities. Dams appeared to
influence these aquatic organisms by degrading habitat and water quality
conditions and fragmenting the river by acting as barriers to fish movement.
Following are highlights of the study results, or ten ways
dams are impacting the Fox River.
• Dams adversely affect fish communities. Based on fish
community index values, free-flowing river reaches (below dam or mid segment
free-flowing stations) averaged a "B" rating or highly valued aquatic
resource, whereas impounded reaches (above dam and mid segment impounded
stations) averaged a "D" rating or limited aquatic resource.
• Free-flowing reaches supported more abundant sport fish
communities than impounded reaches.
• Dams were found to restrict distributions of 30 species of
fish.
• Dams alter and degrade macroinvertebrate communities.
Stations within free flowing reaches of the river had an abundance of
mayflies and caddis flies whereas impounded stations had high proportions
(>95%) of tolerant midge larvae (chironomids) and benthic worms (oligocheates).
• Dams may be preventing freshwater mussel recolonization of
improved sections of river because mussel larvae use fish as a means for
dispersal and dams block fish migrations.
• Habitat quality indices indicated good habitat quality in
the free-flowing river and severely degraded habitat in impoundments.
• The 15 Fox River dams are impounding 47% of river miles and
55% of surface area in the nearly 100 miles of river between the Chain of
Lakes and Dayton, Illinois.
• Nutrient
concentrations (total phosphorus and nitrogen) and algal biomass were
extremely high in the river during the summer low-flow period.
• Dissolved oxygen
concentrations fluctuated widely at impounded stations (2.5 - >20 mg/l), but
not at free-flowing stations (5-8 mg/l). Dissolved oxygen fluctuations
appear to be driven by daytime photosynthesis (oxygen is produced) and
nighttime respiration (oxygen is consumed) of planktonic algae.
• Minimum dissolved
oxygen levels fell below the IEPA recognized standard of 5 mg/l at 9 of 11
impounded reaches of river between McHenry and Dayton, Illinois. Substandard
oxygen sags occurred throughout impounded reaches not just immediately above
the dams, lasted from 1.5 to 16 hours in a 24-hour period, and occurred
during periods of low flow and high water temperature or from July through
September in 2001.
A project final report will be available in May. In the report, we will
summarize all of the data collected during the study and recommend that some
form of fish passage be considered at all Fox River dams. Determining the
correct passage option for an individual dam is a complicated decision
involving many stakeholders (i.e., dam owners, government agencies, local
municipalities, organizations, and the public) and a variety of social,
economic, and environmental issues. Our data suggest that dam removal is the
best option when the ecological health of the river is of prime
consideration. Removing dams will eliminate barriers to migration for all
types and sizes of fish, restore high quality river habitat, and eliminate
lake-like conditions that support high algal biomass and substandard
dissolved oxygen levels. Ramps, fishways, and bypass channels will allow
fish to get over or around dams but will do little or nothing to improve
habitat and water quality conditions in the river. These alternatives should
be considered only when dam removal is ruled out as a fish passage option.
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