Damning Dams

Is One Of The Greatest Engineering Marvels Of The Industrial Age Becoming Obsolete?

An inevitable part of many 1950s science documentaries was an awestruck tribute to our ability to “tame nature”—by building huge dams and controlling the flow of mighty rivers. There are an estimated 800,000 dams on the planet and 40,000 large dams—an incredible 20,000 in China alone.

The really big dams are the largest structures ever built by man, engineering marvels as awe-inspiring as the great pyramids of Egypt. And they rival the pyramids for the sheer magnitude of construction: It took 5,000 workers on 24-hour shifts for five years to build the colossal Hoover Dam.

Photo: Glen Canyon Dam

A growing coalition is trying to remove the Glen Canyon Dam in Arizona and restore the Colorado River’s original flow.

Dams have also brought great benefits to society. In the 1930s, the great era of dam building in the United States, they brought electricity to rural areas. They helped control flooding and brought irrigation to the arid West. Says Marc Reisner, author of Cadillac Desert, the classic account of dam-building in the American West, the Hoover Dam’s “turbines would power the aircraft industry that helped defeat Hitler, would light up downtown Los Angeles and 100 other cities….Hoover Dam proved it could be done.”

But 50 years later, there are signs that these monuments to the industrial age may not be as permanent as their builders planned. In a proposal that would have been unthinkable 10 years ago, a range of groups are calling for the dismantling of Arizona’s Glen Canyon Dam, to restore the Colorado River’s original flow. Even Daniel Beard, former commissioner of the Federal Bureau of Reclamation and once a staunch dam defender, has called for Glen Canyon to be dismantled.

Glen Canyon isn’t the only target of the new dam deconstructionists. Last December, the Quaker Neck Dam in North Carolina became the first big dam to come down. The Edwards Dam in Maine will be removed next summer, and a dam on the Elwha River in Washington will likely be next. As many as a dozen dams are now slated to be dismantled in the U.S., American Rivers reports.

Why the seemingly sudden shift? In many cases, the benefits don’t justify the damage to fisheries and river ecoystems. Studies in Cambodia, Canada, Laos, Thailand, Brazil and many other countries concluded that dams have a significant effect on fisheries—disrupting migratory fish patterns and spawning habits. On the Columbia River in the American west, for example, the estimated cost of losses to salmon fisheries between 1960 and 1980 was $6.5 billion, according to the National Marine Fisheries Service. The World Bank, the largest single international financier of large dam projects, admits that the results of these studies could mean that the bank’s “assumptions about the environmental impact of dams are wrong.”

Steve Glazer, chair of the Sierra Club’s Colorado River task force, sees the effects on western river basins. “Dams have a tremendous impact on natural function in ecosystems,” he says. “Because of the changes in temperature and in water quality, the native fish in the Colorado River are all threatened by the construction of dams.”

New dam construction fragments river habitat the same way a six-lane freeway breaks up land habitat. Juvenile fish are often stranded trying to make the journey to the sea. As reservoirs are filled, severe and immediate flooding leaves river ecosystems significantly altered, and sometimes devastated. But it’s not just the species directly affected that are in danger. Dams prevent the seasonal flooding that create species-rich flood plains. And native species downstream often can’t survive the colder waters released beneath a dam. Estuaries at the mouth of rivers, deprived of freshwater flow, are often devastated as well.

As dam builders move into developing nations, large dams threaten some of the world’s greatest remaining stores of biodiversity. According to Philip Williams, president of the California-based International Rivers Network (IRN), existing plans for six major hydroelectric dams threaten the Mekong, “whose biodiversity is second only to the Amazon and whose fishery and floodplains support much of the population of Cambodia.” The $1.5 billion San Roque Dam in the Philippines, partially financed by the Export-Import Bank of Japan, is the largest private hydroelectric project in Asia, and is expected to cause considerable erosion and damage local fisheries.

And dams are part of a plan to build a 2,000-mile shipping channel into the Pantanal region of Brazil, one of the world’s largest tropical wetlands. In Sarawak, on the island of Borneo in Malaysia, preparations were made for “Operation Noah”—an attempt to relocate some of the 220 mammal and bird species, 104 fish species, and 1,230 plant species, many unique to Borneo—that were threatened by the planned $5.4 billion Bakun Dam. Fortunately, the project was indefinitely postponed in September 1997.

Dams also have incalculable human costs, as people are displaced and archaeological treasures inundated. (Since human civilizations often rise along rivers, riparian areas harbor a disproportionate share of the world’s archaeological sites.) When China finishes its Three Gorges Dam on the Yangtze in 2009, for example, the project will flood an area with 1,208 known historic sites, and displace nearly two million people.

In Silenced Rivers: The Ecology and Politics of Large Dams, IRN’s Patrick McCully estimates that 30 to 60 million people have been displaced by large dams. “The available evidence suggests very few of these people ever recover from the ordeal, either economically or psychologically,” he writes.

“We’re beginning to understand that we need to put ecosystems back into the equation,” says Sandra Postel, director of the Global Water Policy Project. “Even if dams aren’t decommissioned or breached, I think there will be more of an effort to manage them in a way that restores some of the ecological functions that have been lost.”

Even in poor regions like the African Sahel, hard-hit by drought and famine, there is evidence that the benefits dams bring may not outweigh the environmental and human costs. According to a World Resources Institute analysis of a major regional dam project on the Senegal River, many hoped-for economic benefits still hadn’t materialized more than 10 years later. But valley fisheries were devastated, forcing people to truck in fish from the coast. Incidents of bilharzia, diarrheal diseases and malaria increased and surprisingly, nutrition has not improved as expected.

As the true costs of large dams are better understood, governments may learn the value of small-scale solutions. Environmentalists and river advocacy groups urge a better planning process for large dams. They argue that more efficient energy use and water distribution can go a long way toward making new dam projects unnecessary.

Our mighty dams might have been built to last through the ages, but there’s nothing that says we can’t shorten their lifespans.