By Sonya Angelica Diehn
Dams are often touted as environmentally friendly. Although they do represent a renewable source of energy, a closer look reveals that they are far from green. DW lays out the biggest environmental problems of mega-dams.
1. Dams Alter Ecosystems<p>Water is life — and since dams block water, that impacts life downstream, both for ecosystems and people. In the case of the <a href="https://www.dw.com/en/ethiopia-egypt-sudan-make-slow-progress-in-nile-dam-row/a-52015611" target="_blank">Grand Ethiopian Renaissance Dam (GERD)</a>, which is being built in Ethiopia and is set to be Africa's largest source of hydroelectric power, Egypt is concerned it will receive less water for things like agriculture.</p><p>Downstream ecosystems rely not only on water, but also on sediment, both of which are held back by big dams. As solid materials build up in a manmade reservoir, downstream land becomes less fertile and riverbeds can become deeper or even erode away. <a href="https://www.pnas.org/content/115/47/11891" target="_blank">Emilio Moran</a>, a professor of geography and environment at Michigan State University in the US, described sediment loss of 30 to 40% as a result of large dams.</p><p>"Rivers carry sediment that feeds the fish, it feeds the entire vegetation along the river. So, when you stop sediment flowing freely down the streams, you have a dead river."</p><p>And ecosystems may have adapted to natural flooding, which dams take away. </p><p>Mega-dams also often have a large footprint on land upstream. Aside from displacing human communities, flooding to create a reservoir also kills plants, and leaves <a href="https://www.dw.com/en/tanzanias-biggest-wildlife-reserve-under-threat/a-43902762" target="_blank">animals to drown or find new homes</a>. Reservoirs can also further fragment valuable habitat and cut off migratory corridors. </p>
2. Dams Reduce Biodiversity and Cause Extinction<p>Aquatic species, particularly fish, are vulnerable to the impacts of dams. Moran says the Itaipu Dam, which was constructed on the border between Paraguay and Brazil in the 1970s and 1980s, resulted in a 70 percent loss of biodiversity.</p><p>"On the Tucuruí Dam that was built in the 80s in the Amazon," he added, "there was a 60% drop in productivity of fish."</p><p>Many fish species rely on the ability to move about freely in a river, be it to seek food or return to where they were born. Migratory species are badly affected by the presence of dams. In 2016, the International Union for the Conservation of Nature (IUCN) reported a 99% drop in catches of <a href="https://www.dw.com/en/poaching-dams-imperil-ancient-danube-fish/a-43907515" target="_blank">sturgeon</a> and paddlefish — both of which are migratory — over a period of three decades. Overfishing and river alteration were cited as major threats to the species' survival. </p><p>A <a href="http://www.mrcmekong.org/highlights/the-study-on-sustainable-management-and-development-of-the-mekong-river-including-impacts-of-mainstream-hydropower-projects/" target="_blank">2018 study</a> predicted that fish stocks on <a href="https://www.dw.com/en/a-dam-building-race-threatens-the-mekong-river/a-50049206" target="_blank">Asia's Mekong River</a> could drop by 40% as a result of dam projects – with consequences not only for biodiversity, but for the people whose lives and livelihoods depend on those fish.</p><p>The stakes for biodiversity are particularly high for animals threatened with extinction. And not only for aquatic species. The <a href="https://www.dw.com/en/new-orangutan-species-found-in-indonesian-forest/a-41217498" target="_blank">Tapanuli orangutan</a> — the Earth's rarest ape, with only 500 individuals left — could finally be pushed to the brink if a planned hydroelectric project in Sumatra, Indonesia, is completed. Dams can literally snuff out species. </p>
3. Dams Contribute to Climate Change (and Are Affected by It)<p>As reservoirs fill, upstream forests are flooded, eliminating their function as carbon sinks. As the drowned vegetation decomposes, decaying plants in manmade reservoirs release methane, a powerful greenhouse gas. That makes reservoirs sources of emissions — particularly those in <a href="https://www.dw.com/en/forest-sos-earths-green-lungs-disappear/a-44908586" target="_blank">tropical forests</a>, where there is dense growth. It's estimated that greenhouse gas emissions from dams amount to about <a href="https://academic.oup.com/bioscience/article/66/11/949/2754271" target="_blank">a billion tons annually</a>, making it a significant global source.</p><p>And as the climate changes, more frequent and prolonged drought means dams will capture less water, resulting in <a href="https://www.dw.com/en/hydropower-supply-dries-up-with-climate-change/a-42472070" target="_blank">lower electricity production</a>. Countries dependent on hydropower will be especially vulnerable as temperatures keep rising. </p><p>Moran described a vicious circle, for example in Brazil, which gets 60 to 70% of its energy from hydropower: "If you wipe out half the rainforest, there will a loss of half the rainfall. And then there won't be enough water to provide the amount of power from those dams," he explained. </p>
4. Dams Reduce Water Quality<p>Manmade reservoirs trap fertilizers that run into the water from surrounding land. In addition, in some developing countries, sewage flows directly into the reservoirs. This kind of pollution can result in algae blooms that suck the oxygen out of the water, making it acidic and potentially harmful to people and animals.</p><p>Still water in large manmade lakes is warm at the top and cold at the bottom, which can also affect water quality. While warm water promotes the growth of harmful algae, the cold water that is often released through turbines from the bottom of a reservoir may contain damagingly high mineral concentrations. </p><p>In some cases, water in manmade reservoirs is of such bad quality that it is not even fit to drink. </p>
5. Dams Waste Water<p>Since more surface area of the water gets exposed to the sun, reservoirs result in much more evaporation than the natural flow of the river before that dam existed. It's estimated at least 7% of the total amount of freshwater needed for human activities evaporates from the world's reservoirs every year.</p><p>This effect is made worse in hot regions, Moran pointed out. "Certainly if you had a reservoir in a tropical area with high temperatures, there is going to be a lot of evaporation," he said. And big reservoirs "are, of course, evaporating constantly."</p><p>Reservoirs are also a haven for invasive plant species, and weed-covered reservoir banks can lead to evapotranspiration — or the transfer of water from the land to the atmosphere through evaporation from soil and transpiration from plants. Such evapotranspiration amounts to six times more than the evaporation from the water's surface. And there is even evidence that dams increase water use and promote water waste by creating a false sense of water security. </p><p>In the face of <a href="https://www.dw.com/en/water-shortages-pose-growing-risk-to-global-stability/a-50394997" target="_blank">dwindling global freshwater resources</a>, some question whether dams should be reconsidered. </p>
So What Are the Alternatives?<p>The evidence is damning. But if mega-dams have so many harmful environmental effects, what are the alternatives? Although some green groups point to small hydropower as being more ecologically sound, Moran is skeptical. "A dam is a dam - it's blocking the fish, it's blocking the sediment."</p><p>He pointed to the need to consider not just how to maximize energy production, but also maintain ecological productivity. One option he cited is the use of in-stream turbines. </p><p>And many environment advocates agree that other renewable energies such as solar and wind can provide clean electricity at a far lower environmental cost. </p>
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Removing one gigantic dam can have a massive effect on restoring a river ecosystem.
A Group Effort<p>Large dam removals, like those on the <a href="https://therevelator.org/klamath-dam-science/" target="_blank">Klamath River</a> in California and Oregon, or the <a href="https://therevelator.org/save-southern-resident-killer-whales-extinction/" target="_blank">hotly debated Snake River dams</a> in Washington, get lots of media attention. But smaller dam removals are quietly happening all across the country.</p><p>In the past 20 years around 1,100 dams have been removed in the United States — many of them aging, unsafe structures that had outlived their usefulness.</p><p>That's the story in the Cleveland National Forest, too.</p><p>Not a lot is known about the early history of the dams there, but most were likely built in the 1930s by the Civilian Conservation Corps, a public work program started to help Americans rebound from the Great Depression, says Kirsten Winter, a biologist in the Cleveland National Forest who has spearheaded the dam-removal project. It's not unusual for dams to be built in national forests, but this high a concentration of small dams may be a regional phenomenon in Southern California forests.</p>
Before and after dam removal on San Juan Creek in the Cleveland National Forest. Julie Donnell / USFS<p>The project has generated a lot of interest and a diverse array of partners, including California Department of Transportation, Federal Highways Administration, Orange County Parks, Orange County Transportation Authority, the U.S. Fish and Wildlife Service, California Department of Fish and Wildlife, and the U.S. Marine Corps. The coalition has brought funds, organizational support, technical knowledge and a lot of energy to the process.</p><p>"People are really pretty enthused about removing dams," says Winter.</p><p>Despite all the partners, it's still been a learning experience, she adds, because the dams vary so much in size and accessibility. Some are just a few feet high and 10 feet wide. Others reach 14 feet in height and stretch up to 100 feet across.</p><p>To breach the dams and break apart the mortar, crews employed a wide range of techniques. For sites near roads, they bought in conventional excavators. Steeper canyons required the use of a nimble "spider" excavator. Explosives took down a few dams where appropriate, while other places required sledgehammers and jackhammers. An extra bit of muscle (organizational and otherwise) came from a partnership with Marines from nearby Camp Pendleton. Corps members have helped remove 31 dams since 2018.</p>
Ecological Benefits<p>The biggest benefactors of the dam removals in the Cleveland National Forest will be steelhead — a type of salmonid. Like salmon, steelhead are anadromous, spending their time in both freshwater streams and the ocean. But unlike salmon that return to their natal headwater streams to spawn and die, steelhead will often spawn more than once.</p><p>They're also a key indicator species, says Jacobson. "When they disappear, that means there are probably multiple issues within a watershed."</p><p>In the San Juan, dams are one of them.</p>
Endangered Southern California steelhead spawning in Maria Ygnacio Creek in Santa Barbara County, Calif. Mark H. Capelli / WCR / CC BY-NC-ND 2.0<p>"Dams create a very artificial situation," says Winter. "It's not just that they hold water, but they retain sediment and then they create these weird splash pools below."</p><p>Without the dams, the streams are able to create a more natural gradient and pool structure. That's good for other native wildlife like the arroyo toad and the arroyo chub, both federally listed as endangered, as well as the California newt, a California Species of Special Concern.</p><p>While the process of removing the dams can be a bit messy, "we've seen no negative effects to the habitat or to species due to the dam removal," says Donnell.</p><p>One of the biggest concerns with any dam removal is ensuring that any trapped sediment released from behind the structures doesn't cause ecological problems as it moves downstream. But Donnell says they've timed the removals to account for that and the streams naturally carry large sediment loads during storm events.</p><p>"We're actually doing some of dams in phases rather than all at one time because of the sediment load that's being held behind them," she says.</p><p>In areas where dams have been removed, Donnell has already noticed an improvement. "The bedload and sediment transport have been able to naturally flow once again," she says. "And the channel is starting to adjust back to a natural state."</p>
A Connected Watershed<p>As groundbreaking as the Cleveland National Forest's efforts are, the benefits for steelhead hinge on the downstream initiative.</p><p>Just five miles inland from Doheny State Beach, around the town of San Juan Capistrano, two barriers on Trabuco Creek block steelhead from 15 miles of upstream spawning habitat in the San Juan Creek watershed.</p><p>A quarter-mile-long concrete flood-control channel runs underneath five bridges, including the north- and southbound lanes of Interstate 5. The drop and the speed of water flowing through the hardened channel inhibits steelhead from making it through the gauntlet.</p>
Ripple Effect<p>With the dam removals in the Cleveland National Forest nearing completion, Donnell says she's hoping to soon begin presenting her data and methodologies so others can learn from the project.</p><p>"We've definitely heard from other forests and other districts wanting to know how we went about it, because this is new," she says.</p><p>McClain says American Rivers has been sharing the project's success story because it's a good example of how to think holistically about managing water and restoration opportunities for aquatic ecosystems.</p>
San Juan Creek in the Cleveland National Forest shortly after a dam was removed. Julie Donnell / USFS<p>But it also makes sense fiscally. Why spend money maintaining dams we don't need?</p><p>"Even from a federal budget management perspective, we should be looking at where there may be projects on the federal books that are no longer serving a purpose," she says.</p><p>Thanks to the coordinated efforts in the San Juan watershed, southern steelhead will have a better chance of survival. But efforts to try and aid their recovery also have a larger benefit.</p><p>"We're not only restoring their environment, but also ours," Jacobson says. "We're actually improving the rivers overall."</p><p>And in the process, they may have established a model for mass dam removal across the country.</p>
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By Jodi Helmer
Each year, millions of tons of grain make their way along what was once one of our wildest river systems, the Columbia-Snake River. Four dams — the Lower Granite, Little Goose, Lower Monumental and Ice Harbor — erected between 1955 and 1975, ease the way for massive barges bound for ports on the West Coast, and ultimately, markets in Asia. Soybeans, wood products, mineral bulks, and automobiles also travel the river by barge. But outnumbering all other cargo is the soft white wheat grown by farmers from 11 states.
Construction of the Ice Harbor Dam in 1959. US Army Corps of Engineers<p>"When the dams went in, we closed down the rail lines, and, in doing so, barging was the only way to get our grain to market," Jones says. "We don't have the infrastructure to start using rail again, [and] we can't afford to pay another 50 cents a bushel to ship our grain."</p><p>Nevertheless, Jones acknowledges <a href="https://www.nrdc.org/stories/columbia-snake-river-basin-salmon-are-losing-their-way" target="_blank">the steep toll the dams have taken on salmon</a> and is part of a bipartisan, multi-stakeholder coalition searching for fresh ideas to help save them — while supporting farmers, too. Its work is increasingly urgent: From populations numbering 130,000 fish in the 1950s, wild Snake River spring Chinook salmon <a href="https://www.wildsalmon.org/images/factsheets-and-reports/2017.Graphs.Snake.River.Adult.Returns.pdf" target="_blank">dropped to approximately 5,</a><a href="https://www.wildsalmon.org/images/factsheets-and-reports/2017.Graphs.Snake.River.Adult.Returns.pdf" target="_blank">800</a><a href="https://www.wildsalmon.org/images/factsheets-and-reports/2017.Graphs.Snake.River.Adult.Returns.pdf" target="_blank"> in 2017.</a> Thirteen populations are listed under the Endangered Species Act, and all four salmon and steelhead populations in the Snake River Basin are at risk of extinction, according to <a href="https://archive.fisheries.noaa.gov/wcr/publications/gis_maps/maps/salmon_steelhead/critical_habitat/wcr_salmonid_ch_esa_july2016.pdf" target="_blank">NOAA Fisheries</a>. The dwindling number of salmon is having ripple effects across the food chain. In Washington State, only 73 <a href="https://www.nrdc.org/stories/tahlequahs-newborn-and-scarlet-gone-orca-advocates-race-save-their-kin" target="_blank">Southern Resident </a><a href="https://www.nrdc.org/stories/tahlequahs-newborn-and-scarlet-gone-orca-advocates-race-save-their-kin" target="_blank">orcas</a> remain, due in part to the lack of Chinook salmon, their main prey. </p><p>In response, wildlife advocates are renewing calls to <a href="https://www.nrdc.org/experts/giulia-cs-good-stefani/orca-task-force-report-call-action" target="_blank">restore the lower Snake River</a> by breaching the four dams. A <a href="https://nwenergy.org/featured/lsrdstudy/" target="_blank">recent report released by the NW Energy Coalition,</a> with support from NRDC, found that a mixed portfolio of solar, wind, energy efficiency, demand-response, and storage can replace the power the four Snake River dams contribute to the Northwest. Such a change would increase the system's reliability and cost ratepayers little to nothing. A free-flowing Snake River would also safeguard salmon from increasingly hot, even deadly, water temperatures, according to <a href="https://www.columbiariverkeeper.org/our-work-saving-salmon/fighting-cold-water%20Show%20less" target="_blank">modeling done by Columbia </a><a href="https://www.columbiariverkeeper.org/our-work-saving-salmon/fighting-cold-water%20Show%20less" target="_blank">Riverkeeper</a>. "We must break the political logjam around this issue. If we don't, the fish are cooked," says <a href="https://www.nrdc.org/experts/giulia-cs-good-stefani" target="_blank">Giulia C.S. Good Stefani</a>, a senior attorney in NRDC's Nature Program.</p><p>"After looking at the science and economics, our coalition endorsed removing the four dams," says Sam Mace, inland Northwest project director of the nonprofit <a href="https://www.wildsalmon.org/about/save-our-wild-salmon-coalition.html" target="_blank">Save Our Wild Salmo</a><a href="https://www.wildsalmon.org/about/save-our-wild-salmon-coalition.html" target="_blank">n</a>. "It's not the only thing that needs to be done to restore the [salmon] runs to healthy, harvestable numbers, but it has to be the cornerstone of any plan that is going to be successful."</p>
Rethinking Infrastructure<p>The push to restore the river by removing the earthen portion of the dams has been controversial. More than half of U.S. wheat exports are shipped on the Columbia–Snake River system, making it the <a href="https://www.pnwa.net/factsheets/CSRS.pdf" target="_blank">top wheat export gateway in the nation</a> and the third largest in the world. As a result, farmers have the most to lose, according to Sam White, chief operating officer for <a href="http://www.pnw.coop/" target="_blank">Pacific Northwest Farmers </a><a href="http://www.pnw.coop/" target="_blank">Cooperative</a>.</p><p>"You've got people who say, 'Remove the dams at all costs; we want them out, we want to save our salmon,' and then you've got people who are using the river to move products saying, 'No, [the dams] are important to my livelihood,'" White says. "The closer you are to the river, the more economical it is to use the barge."</p><p>But White also estimates that just 40 percent of the region's crops are shipped via barge, down from a high of 80 percent a decade ago. Local farmers have diversified their crops, planting canola, peas, lentils and garbanzo beans, which are shipped through alternate ports reached via trucks or rail. And if rail transportation were built out further, Jones says, farmers like him might be able to abandon barge shipping altogether.</p><p>Already, there is some progress on this front, and models to follow elsewhere in the Columbia Basin, as with the McCoy grain terminal shuttle train loading facility near Oakesdale, Washington, <a href="https://dnews.com/local/new-grain-terminal-breaks-ground-in-mccoy/article_873342c6-1c7c-55b0-9cef-9450c050cc41.html" target="_blank">completed in 2013 with investment from agricultural groups</a>, including the Pacific Northwest Farmers Cooperative. "More companies are trying to make loop rail systems where they can store 100 [railcars] until they're filled with grain and could be economically shipped down to Portland," Jones says. "But that's going to mean building new rail lines or updating older rail lines. A lot of that depends on what finances are put in to [help] companies build rail lines, build storage capacity, and all the things necessary to be able to hold and ship grain."</p><p>Jones believes that offering farmers subsidies to help them adapt to the additional expenses of shipping their grain if dams are removed would be much cheaper than maintaining aging dams. With these supports in place, more farmers would be willing to make the shift, he posits, adding, "I'm pro-dam removal but we have to keep farmers whole."</p>
Spawning Solutions<p>After decades of disagreement, there seems to be a growing awareness on both sides that finding a compromise is essential. At the annual Environmental Conference at the Andrus Center for Public Policy at Boise State University in April, participants came together to discuss the theme, "Energy, Salmon, Agriculture, and Community: Can We Come Together?"</p><p>In his <a href="https://vimeo.com/334511830" target="_blank">lunchtime address</a>, Republican congressman Mike Simpson from Idaho acknowledged that the $16 billion investment in salmon recovery from Bonneville Power Administration, the government agency responsible for delivering electricity from the dams, wasn't working. "I am going to stay alive long enough to see salmon return to healthy populations in Idaho," he went on to say. "You cannot address the salmon issue without addressing dams…they are interwoven."</p><p>Good Stefani, who was a panelist at the conference, met with Simpson this past summer. He's been working with partners around the region, meeting with leaders and decision makers to discuss ways to identify solutions that work for both farmers and fishermen, should the dams come out. "Idaho has had abysmal salmon runs, and that's a huge problem, not just for the ecosystem," she said. "It's also an economic hit to the state. Family and local businesses have paid the price — all the way up the river from Lewiston to Orofino to Riggins to Challis to Salmon."</p><p>One official from Idaho's Department of Labor estimated that salmon and steelhead fishing brings in about <a href="https://billingsgazette.com/outdoors/steelhead-fishing-closure-hammers-idaho-economy/article_481f7f8c-7a85-5a7e-bf5c-029b53b9144f.html" target="_blank">$8.61 million per month</a> to Clearwater and Nez Perce counties alone. But in September, the Idaho Fish and Game Commission had to close all steelhead fishing on the Clearwater River and severely limit fishing on the Snake and Salmon rivers on account of the struggling population. These developments have the local outdoors industry deeply concerned. Last month, a group of <a href="https://www.spokesman.com/stories/2019/dec/08/idaho-outfitters-discuss-grim-salmon-steelhead-out/" target="_blank">about 60 Idaho outfitters and guides met</a> in the Clearwater River Casino near Lewiston to talk about the toll of the closures on their communities.</p><p>Idaho tribes, too, have paid incalculable costs. McCoy Oatman, vice chair of the Nez Perce Tribal Executive Committee, spoke as one of the panelists at the Boise conference. He reminded participants of the importance of salmon as a food source, saying, "we're past the 11th hour" for these fish. "We as tribal people know that."</p>
Taking the Long View<p>In Washington State, tribes and <a href="https://www.ecowatch.com/tag/conservation">conservation</a> groups have ample experience in advocating for dam removal — and maintaining the patience to see their efforts through. Once the decision was made <a href="https://www.nps.gov/olym/learn/nature/elwha-ecosystem-restoration.htm" target="_blank">to </a><a href="https://www.nps.gov/olym/learn/nature/elwha-ecosystem-restoration.htm" target="_blank">remove</a><a href="https://www.nps.gov/olym/learn/nature/elwha-ecosystem-restoration.htm" target="_blank"> the Elwha Dam and Glines Canyon Dam</a>, it took two decades before the final section of the dams were removed in 2014, but the impacts to the river ecosystem were immediate. <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0187742" target="_blank">Research</a> showed that habitats were restored; salmon, steelhead, and trout repopulated the river; and new species moved in.</p><p>Mace believes that sharing those success stories might lead more opponents of dam removal to reconsider their positions. "I have been trying to extend a hand and have conversations with some of the folks that have been traditionally opposed [to breaching the dams], to the communities who use the benefits of the dams, to see if we could come to some kind of understanding at least and see whether there would be a willingness to figure out some solutions," she says. "We are seeing people take more of a long view. They're realizing that the salmon crisis won't go away unless we take some bold actions."</p><p><span></span>In the meantime, Good Stefani takes heart in the dialogues being had at forums like the Boise conference. "When we talk face-to-face, we confront the uncomfortable fact that finding a solution is complicated and there is no villain here," she says. "We have to stop fighting about who has more to lose and start asking what everybody needs. We all want our kids to be able to float and fish these rivers, to know that increasingly rare kind of abundance."</p>
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At least 1,688 dams across the U.S. are in such a hazardous condition that, if they fail, could force life-threatening floods on nearby homes, businesses, infrastructure or entire communities, according to an in-depth analysis of public records conducted by the the Associated Press.
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By Paula Ezcurra and Octavio Aburto
Thousands of hydroelectric dams are under construction around the world, mainly in developing countries. These enormous structures are one of the world's largest sources of renewable energy, but they also cause environmental problems.
The dammed Fuerto and Santiago Rivers show greater erosion where they reach the Pacific coast than the free-flowing San Pedro and Acaponeta rivers. Images at right show coastline changes during the two periods: blue indicates land accretion, red indicates erosion.
Ezcurra et al., 2019., CC BY-NC
Vegetation profile of sandbars of the free-flowing San Pedro River (A) and dammed Santiago River (B), where receding black mangrove forest is being eroded away into the advancing coastline
Ezcurra et al., 2019, CC BY-NC
Only a little more than one-third of the world's 246 longest rivers remain free-flowing, drastically reducing the diverse benefits that healthy rivers provide to people and nature everywhere, according to a new study by World Wildlife Fund (WWF) and partners.
By the Numbers
5: Priority recommendations that the U.S. Environmental Protection Agency (EPA) has implemented since March 2018. Those actions relate to chemical standards, nonpoint water pollution and water pollution assessment. There are, however, 14 priority recommendations that the agency has not acted on. (Government Accountability Office)