AUSTIN, TEXAS — Hydropower, a renewable energy source often overshadowed by excitement about wind and solar power, is enjoying something of a global resurgence.
Huge, controversial dam projects have recently made headlines in Brazil, Chile and Laos. Many developing countries, hungry for energy to supply their growing economies over the long term, are determined to keep building more modest-sized dams too.
Record amounts of hydropower capacity came online in 2008 and 2009, the most recent years for which data are available, according to Richard Taylor, executive director of the International Hydropower Association in London.
“There has been, over the last decade, a dramatic increase in the deployment of new hydropower capacity,” Mr. Taylor said.
The private sector, he added, has become more willing to provide financing for projects, which include not only the construction of new dams but also the modernizing of existing ones in places like Europe and the United States. The biggest new dams can cost billions of dollars.
But the renewed attention to hydropower, which accounts for about 16 percent of the global electricity mix, comes with environmental red flags. More attention than ever focuses on people who face displacement, as well as the effects of new dams on land and fish.
In Chile last week, demonstrators protested against a government plan to dam two rivers that wind through a wild, remote part of Patagonia. Last month, officials from Southeast Asian countries failed to reach an agreement about a proposed dam project on the Mekong River in Laos, amid concerns from Vietnam, Cambodia and Thailand about downstream implications.
An additional environmental issue — one that has caused mounting concern in recent years — is climate change. Changes in rain or snowfall patterns can drastically affect the amount of power a dam produces and also the amount of sediment flowing through the river.
Prolonged droughts are already taking their toll. Brazil, which gets about 80 percent of its electricity from hydropower, experienced a bad drought about a decade ago, and Chile has struggled with drought, too, according to Deborah Lynn Bleviss, a professor in the energy, resources and environment program at Johns Hopkins University’s School of Advanced International Studies in Washington.
A 2009 drought took a toll on countries including Guatemala, Venezuela, Argentina and Uruguay, as well as Brazil, she said.
“All have had impacts on hydropower capacity in these countries,” Ms. Bleviss said in an e-mail.
The region around Three Gorges Dam in China, the largest hydropower project in the world, is coping with a severe drought that has closed part of the Yangtze River to shipping, according to the state-run China Daily newspaper.
Small hydropower projects are especially vulnerable to climate change, according to Leandro Alves, who heads the energy division for the Inter-American Development Bank’s infrastructure and environment department, because they may not have enough reservoir storage capacity to compensate for decreased precipitation.
However, some dams may get more water, not less, as the climate changes. In a summary report on renewable energy released last week, the Intergovernmental Panel on Climate Change said that the effect of climate change would vary depending on a project’s location.
“For hydropower the overall impacts on the global potential is expected to be slightly positive,” the report states.
“However, results also indicate the possibility of substantial variations across regions and even within countries.”
In Norway, which gets nearly all of its electricity from dams, climate change on balance may benefit hydropower plants. “The studies have uncertain results, but the main result is that climate change on average will lead to more rain and thereby better production capability in Norwegian power plants,” said Tor Arnt Johnsen, who heads the analysis section of the Norwegian Water Resources and Energy Directorate, which is part of the Ministry for Oil and Energy, in an e-mail.
However, he noted, climate change is expected to lead to substantial weather variations. Thus, in especially dry and cold years, the dams are likely to produce less electricity, which could result in high electricity prices and the need to import power.
