When it is completed in 2015, the Jirau hydroelectric dam will span the Madeira River, feature more giant turbines than any other dam in the world and hold as much concrete as 47 towers the size of New York’s Empire State Building.

And then there are the power lines, draped along 2,200 km of forests and fields to carry electricity from the middle of South America to Brazil’s urban nerve center, Sao Paulo.

Still, it won’t be enough.

The Jirau Dam and the Santo Antonio complex that is being built a few kilometers downstream will provide just 5 percent of what government energy planners say Brazil will need in the next 10 years.

So the country is building more dams, many more, courting controversy by locating the vast majority of them in the world’s largest and most biodiverse forest.

“The investment to build these plants is very high, and they are to be put in a region which is an icon for environmental preservation — the Amazon,” said Paulo Domingues, energy planning director for Brazil’s Ministry of Mines and Energy. “So that has worldwide repercussions.”

In the years between now and 2021, the Energy Ministry’s building schedule will be feverish: Brazilian companies and foreign conglomerates will put up 34 sizable dams in an effort to increase the nation’s capacity to produce energy by more than 50 percent.

The Brazil projects have received less attention than China’s dam-building spree, which has plugged up canyons and bankrolled hydroelectric projects far from Asia.

But Brazil is undertaking one of the world’s largest public-works projects, one that will cost more than $150 billion and harness the force of the continent’s great rivers.

The objective is to help the country of 199 million people achieve what its leaders call destiny: becoming a modern and efficient world-class economy with an ample supply of energy for office towers, assembly lines, refineries and iron works.

“Brazil is a country that’s growing, developing, and it needs energy,” said Eduardo de Melo Pinto, president of Santo Antonio Energia. “And the potential in energy production in Brazil is located, for the most part, in Amazonia.

“And that’s why this is important for this project to be developed.”

The Jirau, Santo Antonio and other projects, though, have until now generated more tension than electricity, raising questions that range from their environmental impact to whether future generations will be saddled with gigantic debt.

International Rivers, a U.S.-based environmental group that has tracked government agencies involved in the dam building, says plans call for 168 dams to be completed by 2021.

Most of the dams are small facilities that will be used to regulate water or to power silos, mineral extraction facilities and industrial complexes.

But whether the dams are large or small, homesteaders and Indian leaders say that the dams will cause irreversible changes in a forest that plays a vital role in absorbing the world’s carbon emissions and regulating its climate.

Across Brazil, rivers are being diverted. Canals and dikes are being built. Roads are being paved, and blocks of concrete are being laid across a network of waterways that provides a fifth of the world’s fresh water.

And the big dams will inundate at least 6,500 sq. km of forests and fields — an area larger than the American state of Delaware or the Middle Eastern nation of Brunei.

Environmentalists say the dams are a throwback, not the kind of projects a modern, democratic country should be aggressively pursuing. They say Brazil should focus instead on developing wind and solar energy while overhauling existing plants and instituting other reforms to reduce electrical demand.

“This is a sort of 1950s development mentality that often proceeds in a very authoritarian way, in terms of not respecting human rights, not respecting environmental law, not really looking at the alternatives,” said Brent Millikan, Amazon program director in Brazil for International Rivers.

In a swath of Rondonia state, along the BR-364 highway, several residents said the dams had uprooted communities of subsistence farmers and fishermen, unalterably changing their way of life for the worse.

Telma Santos Pinto, 53, said she had to leave her home of 36 years, receiving the equivalent of $18,000 as compensation from the companies building the Jirau Dam.

“The compensation was very, very low,” she said. “And we were obligated to accept that.”

Her town, Mutum Parana, was left underwater. Most of her neighbors moved into Nova Mutum — or New Mutum — a town of 1,600 homes, schools, churches and stores put up by the builders of Jirau.

“We were a community, all of us united,” she said. “All of us helped each other.”

Such laments come up against the hard economic realities that Brazil faces.

By 2021, the economy is projected to expand by 63 percent, the Energy Ministry says.

Hundreds of thousands of people are receiving electricity for the first time each year, and a ballooning middle class is consuming more.

Economic planners also predict that Brazil could become the world’s fifth-largest economy in a few years.

No Brazilian leader is more focused on that objective than President Dilma Rousseff, a former 1970s guerrilla who was energy minister in her predecessor’s government.

She says that Brazil is “privileged” to have so much water and that it is logical for the country to rely heavily on hydropower.

She counters environmentalists by arguing that Brazil’s energy mix — the country also relies on solar, wind and biomass, all renewable energy sources — is among the world’s cleanest.

“Economic growth is not contrary to the best environmental practices,” Rousseff said at the inauguration of one huge dam in October.

“We are proving that it’s possible to increase electrical generation and at the same time respect the environment.”

To be sure, the footprints of the new dams will be smaller than those of the past.

The proposed Belo Monte project on the Xingu, a huge dam that has galvanized environmentalists and Hollywood luminaries, will flood fives times less land than the 29-year-old Tucurui Dam, Brazil’s second-biggest, said Domingues, the energy ministry planner.

The Jirau Dam includes ladders to help migrating fish make it upstream and conservation programs for animal and bird life.

Gil Maranhao, the dam’s communications and business development director, said “the real deforestation is maybe zero” because the flooding has taken out cattle ranches and small subsistence farms rather than large swaths of forest.

He said the $7.7 billion project has created jobs and prompted the consortium building the dam to spend $600 million on social programs and housing for the 350 families that had to be relocated.

“The impacted population move from slums without electricity, without sewage, and we put them in new cities built for them,” he said, pointing to Nova Mutum.

Jose Gomes, a civil engineer who is the project’s institutional director, said rigid requirements ensured that the environmental impacts of the dam and the Santo Antonio complex were minimized.

Building dams, he said, here and elsewhere in the country, is a major priority that will not be derailed.

“Brazil needs two hydroelectric dams like this to provide power each and every year,” Gomes said. “We’re going to have energy guaranteed.”

Cranes stretch into the sky and steel reinforcements are going up. Although the turbines are not yet operating, the power houses are firmly installed.

Upriver, more than 250 sq. km of land lies underwater.

It is clear that the mighty Madeira River, the biggest tributary of the Amazon River, has been tamed.