U.S. Water News Online
MISSOULA, Mont. -- Rivers rebound within a year after dams
are removed, an ecologist told scientists at a meeting in this city
near Milltown Dam, targeted for removal.
Fish have exceeded expectations in re-establishing migratory
routes, and it's a myth that smelly mud flats are left in the former
reservoir, Emily Stanley said.
She studies the ecological effects of dam removal with her
graduate students at the University of Wisconsin, and spoke at a
workshop sponsored by the University of Montana.
Stanley warned that when a dam is removed from a river, sediment
is redistributed and that can bring trouble, at least in the short
term, for some aquatic life downstream. She also said communities
often lament loss of their backyard reservoir and the fish and
wildlife it sustained.
Some of her comments were for state and federal regulators
overseeing the planned removal of Milltown Dam on the Clark Fork
River just east of Missoula.
"Within a month or two, the reservoir greens up,'' she said,
showing the newly green flats after removal of Rockdale Dam in
"But for people who live on a reservoir, two months is too long.
So we help nature along a little.''
On the Rockdale Mill Pond, state officials used a crop-duster to
spread winter rye and prairie flower seeds. They saw results in less
than two weeks.
Over time, vegetation grows in former reservoirs, but Stanley
cautioned that what appears sometimes is non-native and weedy.
"In Wisconsin, the strategy has been to get the seed in early so
it blocks the invasion,'' she said. "Sometimes it works. Sometimes it
Stanley has found fish studies positive.
On Wisconsin's Baraboo River, where seven dams were removed,
migratory species re-established long-abandoned historic routes
within a year. Eight of 16 migratory species not previously found
above the dams were quickly traveling past the former blockades,
"There was this huge celebration when they saw the first river
sturgeon migrate through Baraboo,'' she said. "They hadn't seen
sturgeon there in 150 years.''
Fishermen were ecstatic, especially when the caddis flies and
stoneflies returned "and the river remembered how to be a river,''
Not all fish migrate and the downstream movement of reservoir
sediment "can hammer the resident fish,'' she added.
"We still have an enormous amount to learn about fish. There are a
lot of opportunities for research into their biology and behavior.''
Stanley cautioned that although dam-removal projects often are
considered good, scientists and government officials must remember
reservoirs have their proponents.
"While I like rivers, reservoirs are important to the people who
live by them,'' she said. "So don't dismiss the significance of the
event (dam removal) to those communities.''
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