06 Aug 2015: Opinion

Undamming Rivers: A Chance
For New Clean Energy Source

Many hydroelectric dams produce modest amounts of power yet do enormous damage to rivers and fish populations. Why not take down these aging structures, build solar farms in the drained reservoirs, and restore the natural ecology of the rivers?

by john waldman and karin limburg

Hydroelectric power is often touted as clean energy, but this claim is true only in the narrow sense of not causing air pollution. In many places, such as the U.S. East Coast, hydroelectric dams have damaged the ecological integrity of nearly every major river and have decimated runs of migratory fish.

This need not continue. Our rivers can be liberated from their concrete shackles, while also continuing to produce electricity at the site of former hydropower dams. How might that occur? A confluence of factors — the aging of many dams, the advent of industrial-scale alternative energy
Conowingo Dam
American Rivers
If Maryland's Conowingo Dam were removed, large-scale solar projects could be built on the site of its drained 9,000-acre reservoir.
sources, and increasing recognition of the failure of traditional engineering approaches to sustain migratory fish populations — raises fresh possibilities for large rivers to continue to help provide power and, simultaneously, to have their biological legacies restored.

The answer may lie in “sharing” our dammed rivers, and the concept is straightforward. Remove aging hydroelectric dams, many of which produce relatively small amounts of electricity and are soon up for relicensing. When waters recede, rivers will occupy only part of the newly exposed reservoir bottoms. Let’s use these as a home for utility-scale solar and wind power installations, and let’s employ the existing power line infrastructure to the dams to connect the new solar and wind power facilities to the grid. This vision both keeps the electricity flowing from these former hydropower sites, while helping to resurrect once-abundant fish runs, as has recently happened in Maine.

More than a half-century of modern attempts to allow fish to traverse what often are sequences of dams that block access to their historical spawning reaches in eastern U.S. rivers presents a dismal record. Highly unnatural
No other action can bring ecological integrity back to rivers as effectively as dam removals.
conveyances such as fish ladders are often only marginally helpful to fish on their upstream spawning runs, which is one reason why some migratory fish runs have fallen as much as five orders of magnitude. Take Atlantic salmon, a revered game and food fish that once may have numbered a half-million in U.S. rivers. In 2014, fewer than 400 attempted to reach their New England spawning grounds. Such relict populations are often protected from harvest, yet are still not meaningfully restored.

No other action can bring ecological integrity back to rivers as effectively as dam removals. Yet such efforts may come at the cost of a loss of hydropower. And so what many hoped would be a precedent-setting breaching of the Edwards Dam on Maine’s Kennebec River in 1999 — which had yielded only 3.5 megawatts of power — has not been followed by the dismantling of other, higher-wattage dams on the East Coast.

Yet, the efficacy of dam removal to restore migratory fish was shown in the Kennebec after the Edwards Dam fell; for the first time in more than a century-and-a-half, alewives, a species of herring, were able to access an upriver tributary, the Sebasticook. Within just a few years the Sebasticook’s run of alewives swelled from non-existent to almost three million, supporting scores of bald eagles and an “alewife festival” that celebrates the Sebasticook’s extraordinary renewal.

In “sharing” a river more equitably between energy production and its ecological imperatives, the critical step would be the breaching of existing dams. Though that may seem improvident — if not downright radical — it is important to remember that many of these concrete walls are middle-aged or older and will be reaching their life expectancies in the
In breaching a dam and draining a reservoir, substantial areas of land could become available for new uses.
coming decades. Deteriorating dams are a serious public safety concern — one likely to increase as climate change generates more frequent and intense storms.

We believe the compelling ecological and impending structural reasons for dam removals should be considered in light of the rapidly evolving national energy landscape, and that, together, they signal exciting possibilities for a dramatically improved stewardship of major rivers. Fortunately, traditional hydropower facilities already offer the real estate that lies under reservoirs and existing electrical transmission lines that could be used by renewable energy sources.

In breaching a dam and draining a reservoir, substantial areas of land could become available for new uses. Take the Conowingo Dam in Maryland, for example. The Conowingo is the largest of four hydroelectric dams on the lower 55 miles of the Susquehanna River and sits only nine miles above the head of Chesapeake Bay. Its 572-megawatt capacity is fed by a 9,000-acre reservoir that also serves as an emergency water supply for Baltimore, and provides water for cooling intakes at the nearby Peach Bottom nuclear plant. The pool is also used by recreational boaters and fishers.

If the Conowingo Dam were removed, this would free up more than enough area to replace the lost hydroelectric generation with power from solar parks along the former reservoir bottom, and allow for other land uses, such as creation of fringing wetlands and forests. For comparative scale, California’s new, 392-megawatt Ivanpah Solar Electric Generating System has three units occupying 3,500 acres. More sun shines on the Mojave than in the mid-Atlantic region, but according to the National Renewable Energy Laboratory calculator, acre for acre, the Conowingo region should support 76 percent of the power-generating capacity of the desert. Thus, about three-quarters of the river bottom would need to be in solar to match the output of Ivanpah.
Although manmade reservoirs have their aficionados, rivers often have more of them.

One other issue facing the Conowingo Dam removal would be the sediments behind the dam that would need to be stabilized. The reservoir itself is close to capacity, and current plans are to dredge the pool, at an estimated cost of $48 million to $267 million annually. Those who are concerned for the ecological health of the Chesapeake Bay fear that if the dam is removed, millions of tons of sediment, enriched with nutrients and, potentially, toxic substances, could pour into the bay. But sediment stabilization is routinely done in dam removals and could be safely accomplished with careful design and engineering.

Finally, what of the pushback by those who cherish the status quo? Few local residents were alive when the Conowingo Reservoir began filling in 1928, so the big pool is their cultural heritage. Surely, any such drastic change would be hotly debated in many forums. But only a small number of houses exist on the 29 miles of shoreline that would be affected if the reservoir were removed.

The same issues were faced in the debates about removing mainstem dams in the Penobscot River in Maine, and eventually a consensus emerged there. Preservation of power generation (diverted to smaller tributaries) was important to closing the deal, and will likely be important in other cases. And although manmade reservoirs have their aficionados, rivers often have more of them — the scores who appreciate the fishing, paddling, and nature watching they provide. One study showed large economic benefits from the Edwards Dam removal.

And what about the nuclear plant, and Baltimore’s emergency water supply? The Peach Bottom plant could install water-miserly, closed-cycle cooling towers, and Baltimore could still withdraw water from the
Perhaps hydro companies should not continue to act as gatekeepers for what could be healthy rivers brimming with life.
Susquehanna in an emergency.

There are other potential tools available to help share rivers. Any remaining backwater ponds could be outfitted with floating solar panel arrays, as used successfully in Japan. Also, because reservoirs are nestled in valleys, in some instances the surrounding ridges might host wind turbines. Though combined alternative energy sources such as these might alone make up or exceed the original hydropower lost, “run of the river” hydropower — in which only a portion of the current is routed through turbines — could also contribute. But, critically, while generating some hydropower, the river’s mainstem would remain free-flowing, opening the way for resurgent fish migrations.

On the Penobscot River, the precedent of restoring a major river while maintaining equivalency of energy production was recently accomplished. This was done by increasing hydroelectric generation capacity on a set of tributaries while reopening the mainstem channel through dam removals and more effective fishways — thus returning nearly 1,000 miles of river habitat to eleven species of sea-run fish, including Atlantic salmon, sturgeon, and river herring. Other, once biologically productive New England rivers now clogged with multiple dams — such as the Kennebec, Merrimack, Connecticut, and Housatonic — could be prime candidates for some of these new ways of thinking about the future of rivers.

Other innovative approaches could also be explored. The previously submerged but newly available riverfront property might be sold or


A Successful Push to Restore
Europe’s Long-Abused Rivers

Polar water acidification
From Britain to the Czech Republic, European nations have been restoring rivers to their natural state — taking down dams, removing levees, and reviving floodplains. For a continent that long viewed rivers as little more than shipping canals and sewers, it is a striking change.
transferred for conservation easements or for parks or even environmentally sensitive residential development. The revenue from these sales could be used for solar or wind projects in other promising but underutilized locations, such as landfills and urban brown fields.

A discussion of new strategies is timely because we are about to double-down on the flawed status quo. The Federal Energy Regulatory Commission will be evaluating many East Coast hydro dams for relicensing within the next few years — licensing that would lock in the failed fish passage paradigm for as much as an additional half-century.

As two conservation biologists who study rivers, we believe it’s time to explore a dramatically different vision. It may be that hydro companies should not continue to act as the gatekeepers for what could otherwise be healthy rivers brimming with life. Certainly, society requires electrical power, and rivers already are part of our grid. The way forward just may be to share a river more equitably between renewable energy production and its natural ecology.

POSTED ON 06 Aug 2015 IN Biodiversity Energy Forests Policy & Politics Water Asia North America 


The dam removal arguments are sound, but the idea to cover the reservoir area with solar panels instead of letting it become productive riparian habitat again is a terrible idea. These reservoir areas are extremely important restoration areas for the river, fish, preventing erosion, reconnecting wildlife coordinates, shading flows.... Solar panels should be on rooftops not next to rivers.
Posted by William on 07 Aug 2015

Placing structural elements like solar panels and wind turbines in or near a flood plain is folly. Not to mention the ugliest thing I can think off. I much prefer the sight of a lake/ reservoir to 500 wind turbines or 5,000 solar panels. What new wave thinking is this? Hydropower and its associated reservoir offer multiple uses unlike solar arrays and wind turbines. Please factor those thoughts into your desire to erase hydropower.
Posted by Phil on 07 Aug 2015

And how do you propose to tell the thousands of travelers who commute to work, school, etc. over US Route 1, which is part of the Conowingo Dam?
Posted by Jane Bellmyer on 08 Aug 2015

Other issues at stake, at least in the West, are goods/commodity transport through the lock systems, irrigation water to support your food supply and flood control for down-river communities. Energy is not the only reason dams were built in years past.
Posted by Jason on 10 Aug 2015

“It always seems impossible until it's done.”
― Nelson Mandela

So take heart, those of you who would make a start on putting this broken world back together. If enough ideas like this are implemented there may still be hope for our grandchildren although the time is getting very late.
Posted by John F. Dunbar on 12 Aug 2015

Removing hydroelectric projects on rivers may not have any problem as equivalent power can be produced through alternatives. But what are the implications of undamming irrigation projects. What are the alternatives for reaching water to farmers? All major dams in India are multipurpose. They include irrigation and power generation.
Posted by K Babu Rao on 15 Aug 2015

Have you considered capacity factor?

They hydro plant probably has a capacity factor between 30 and 65\%. Ivanpah, your reference solar facility, had a capacity factor of 14.9\% from April '14 through March '15.

76\% of 14.9\% is 11.21\%. The 76\% number you cite may not be credible, as NREL has overestimated renewable energy capabilities regularly. However, even allowing the credit of that number, have you thought about where you are getting the rest of the electricity that the hydro plant produced?

I agree the dams should come out for ecological reasons, but the notion that they can be readily replaced with intermittent renewable energy facilities occupying a portion of the former lakebed seems mathematically unsupportable.

Energy is not that easy.
Posted by Frank Jablonski on 19 Aug 2015

A good piece that is unfortunately too narrowly
focused. Irrigation and flood control need to be
addressed. Then too, you can't replace base-line
continuous power with only intermittent sources.
Worse, those intermittent sources gobble a
tremendous amount of land to generate equivalent
year-round energy as a hydro, coal, gas, or nuclear
plant. There are solutions and the authors need to
dig a little deeper.
Posted by BillB on 17 Sep 2015


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john waldman and karin limburgABOUT THE AUTHORS
John Waldman, a professor of biology at Queens College, New York, works on the ecology and evolution of anadromous fishes, historical ecology, and urban waterways. Karin Limburg is a professor of environmental biology at the SUNY College of Environmental Science and Forestry. She studies human impacts on watersheds, rivers, estuaries, and coastal oceans, particularly effects on fisheries.



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