Data from largest U.S. dam removal could shape future river restoration, scientists say

Reports Chicago • Miércoles, 7 de Diciembre de 2011

DEC 01, 2011

Standing at the edge of a two-lane highway in Olympic National Park in Washington State, biologist Kim Sager-Fradkin looked out over Lake Aldwell. Above the reservoir, clouds sat low over mountains coated by thick, dark green forests of Douglas fir, cedars and hemlocks and splashed with yellowing foliage of big leaf maples.

“Since the dam removal started, this lake has dropped incredibly,” Sager-Fradkin said. “We can see the channel flowing, we can see a lot of sediment down there. And we can actually see a river coming back.”

Lake Aldwell’s transformation is the result of a dam removal project currently underway. The removal of two dams on the Elwha River, the largest dam deconstruction project ever undertaken, is expected to have dramatic effects on renewing wildlife habitats and the natural landscape, she said. With the dams gone, 70 miles of prime habitat will be reopened.

Sager-Fradkin, head wildlife biologist for the Lower Elwha Klallam tribe, is one of many scientists working furiously to gather data that will demonstrate the ecological benefits of dam removal.  Researchers expect that fish, otters and other wildlife will soon return to the area.

“Everyone’s hope is that this is setting the stage for other ecological restoration projects elsewhere, and that we’re leading the charge and showing what can happen when you take a dam out of a river,” she said.

Dams, dams everywhere

Dams had their heyday from the early 1900s until the 1960s. They were used for hydropower, flood control, recreation, storing potable water, cooling power plants and for aesthetic reasons. Now, many of the dams are deteriorating, reaching the end of their working lives.

This year, dam removal projects include the Elwha dams (September) and the Condit Dam near White Salmon, Wash. (October). More dam removals have also been announced. On Nov. 23, the Great Works Regional Land Trust announced the removal of Shorey's Brook dam near the Simone Savage Wildlife Preserve in Maine to restore fish habitat. However, the number of removals is small compared to the number of standing dams in the United States.

Over 75,000 dams at least 2 meters high cut through rivers across the United States and approximately 85 percent will reach the end of their operational design by 2020, according to researchers Emily Stanley of the University of Wisconsin in Madison and Martin Doyle of Duke University, Durham, N.C.. Often, life expectancy is about 50 years, Stanley said. There are over a thousand dams  in Illinois alone, with 445  of them being over the age of 50, according to the American Society of Civil Engineers.

The Illinois Department of Natural Resources in 2007 identified 25 dams in the state needing to be upgraded. Of those 25 dams, 15 dams were earmarked for potential removal. The lowest preliminary removal estimate was $270,000 for the Riverside Dam on the Des Plaines River. The highest was a hefty $8.3 million cost to remove the Lower Sterling Dam on the Rock River. The reason for removal is related to safety, said Nick Textor, a senior civil engineer who worked with the American Society of Civil Engineers on their dam study.

A more extensive dam-removal project is also underway in Illinois. The Des Plaines River, running west of Chicago and north to Wisconsin, may become completely dam-free in the next few years. The U.S. Army Corps of Engineers has removed three of the nine low-head dams on the river and plans to finish the job in the coming years. The concrete dams, originally installed for aesthetic reasons, have posed an obstruction to the natural movement of fish, as well as affected the river flow and adjacent floodplains.

Some dams, such as the dam at the Necedah Wildlife Refuge in central Wisconsin, are fostering habitat preservation, said Emily Stanley, a professor of zoology at the University of Wisconsin. However, many believe that a large percentage of dams no longer serve a purpose.

“A lot of them, frankly, are not doing anything,” Stanley said. “A lot of dams were built to do things like generate hydropower or run mills, but that is a bygone era. They are often not generating revenue and, in some cases, they may become an economic liability if insurance becomes required by a state agency.”

In terms of green energy, most dams do not make a significant contribution, said George Pess, fishery biologist at the National Oceanic and Atmospheric Administration. He believes more dam removals are imminent.

“There’s efficient green energy and there’s inefficient green energy,” he said. “If you have old dams that are inefficient and that need a lot of money to be maintained over time, why not take them out and put your resources toward things that might be more efficient?”

However, just because many dams will be structurally or functionally retired, does not mean that they will all be removed, Stanley said.

“The reality is that there isn’t much funding to do with them, so in the case of Wisconsin, when a dam is structurally compromised, it has to become a really precarious situation before the agency can do anything about it,” she said.

Pat Crane, a fisheries biologist in Olympic National Park, near Forks, Wash., said although the removal of dams will be on a “case-by-case basis,” he anticipates more dam deconstruction throughout the country. “Not only because it is the environmentally right thing to do, but a lot of these structures are obsolete, have reached their life expectancy, maybe are orphaned in the case of the Manatawny Creek Dam.”

Environmental and cultural compromises

In the case of the Elwha Dam and several other dam removals, one of the primary reasons for dam deconstruction is to restore fish habitat.

In Olympic National Park, salmon are born in the rivers and then travel to the sea where they gain 90 percent of their body weight, Pess said. When the salmon return to the same rivers to spawn, many of them are eaten or die naturally. The marine-derived nutrients in the fish then transfer to the riparian zone and have a positive effect on local species, Pess said.

“Those nutrients get distributed across the ecosystem and actually increase the growth rate in animals and [improve] their condition, enhancing their survival over time,” he said.

The importance of having fish in a riparian zone is recognized across the United States.

“Fish are definitely mobile nutrient-vectors, and it’s not just moving the nutrients out into the riparian areas, it’s whatever role they play as a grazer or predator up in these aquatic habitats,” Stanley said. “Dams removed a member of the community that should have been there.”

She called fish migration “a pretty common phenomenon” and said that with the return of fish to a riparian area, “habitats will become healthier.”

The impact fish have on rivers is not just environmental - fish also play an important cultural role for communities, said Frances Charles, the tribal chairwoman of the Lower Elwha Klallam Tribe in Washington State.

“It has an impact on our livelihood, it has an impact on the food source,” she said. After the removal of the Elwha dams, the tribe will honor a five-year moratorium on fishing to help the salmon runs return to a healthy level.

“Our cultural rights will have to be built again,” Charles said. She added that she supports the removal of dams elsewhere in the country.

Marilyn Edgington, who came to the Elwha Reservation after the dam was built, said she has only heard stories about the large runs of fish from elders. Although she is not sure that she will live to see the fish return, she said she does have one wish.

“I hope that my grandchildren can see the fish come back,” Edgington said.

Considerations in dam removal

In the case of the Midwest, there are additional factors to consider with dam removal. While it is “reasonable” to expect native species to recolonize, there are some instances when leaving a retired dam in place may be a good idea, according to Matt Catalano, a post-doctoral research associate at Michigan State University, East Lansing, Mich.

“Another issue to think about is the invasive species,” he said. “Some of the dams might be keeping out invasive species such as Asian carp.” If Asian carp were to move through the rivers, they could colonize other places, such as Lake Eerie, Catalano said.

In addition to invasive species, the initial release of sediment should always be considered, said Stanley.

If a dam is removed quickly and not very carefully, a release of sediment can smother downstream areas. After time, however, positive environmental effects appear, Stanley said.

“In continuing to follow these sites over a longer time period, we see things like rapid upstream movement of fish into areas of the river where they haven’t been in 100 years,” she said. “We see the sediments get colonized quickly by plant communities and a quick return of classic river aquatic communities.”

These risks have not stopped some dam removal projects in the Midwest, Catalano noted.

Catalano did his master’s research on the Baraboo River in Wisconsin, where four dams were removed to allow native species, like the lake sturgeon, to return.

“There were accounts from people that lived there in the 1800s of sturgeons that came up the river, and they wanted a run of big, majestic sturgeon coming back,” Catalano said.

The experience is consistent with Pess’s belief that, once the decision to remove a dam is made, natural processes will soon reinstate themselves.

“The beauty of reconnecting a system is that these systems know what to do with themselves,” said George Pess. “You don’t need to teach an ecosystem what to do, you just need to give it the opportunity to do it.”

Indeed, when the four dams were removed from the Baraboo River in Wisconsin, fish began moving upstream in less than a year.

“This is just what fish do, they are travelers,” Stanley said.

In the case of the Elwha River, Pess said he believes there will be a one- to four-fold increase in salmon in the next 10 to 20 years.

Elwha serves as an example

Information gathered from the removal of Elwha River dams will be helpful in deciding what to do with dams across the United States, Stanley said.

“I think it’s going to be a very important example,” she said. “It’s one that I’m keeping my eye on.”

Although Stanley and other researchers in the Midwest have done a lot of work on small dam removal, the size of the Elwha project will help scientists better understand issues with sediment and ecosystem restoration, she said.

“What we learn from the Elwha example will be extremely important in what we can and can’t do in removing big dams and what is and isn’t possible with restoring big rivers,” she said. “I think that’s a lesson that dam managers will be interested in knowing.”

The testament of Native American communities and those who work with them is also a strong case for removing obsolete dams and refraining from building new ones.

“Look at the effect on human and animal populations,” Fradkin-Sager said. “Is it really worth it? I would argue no.”

In disconnecting a river, said Pess, you cause disruption to the communities that depend on it.

“People in a lot of places evolved with those natural cycles,” he said. “If you disrupt those natural cycles, that can have a profound effect in how people live and raise their children and ultimately survive,” he said.

Although the Elwha Dam removal is a huge project, the lessons about preserving the ecosystem and the cultures around the dam are universal.

“The bottom line is if you put in a dam, you are fundamentally disconnecting a system,” Pess said. “Whether you’re talking about a small creek that has a small push-up dam or the Nile, it will have a profound effect on a variety of things.”

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