This article is part of a special National Geographic news series and initiative on global water issues.

Ethiopia has announced that it will construct a controversial multibillion-dollar Nile River dam that could supply more than 5,000 megawatts of electricity for itself and its neighbors, including newcomer South Sudan.

The project—the Grand Millennium Dam—has sparked worries about environmental and human costs and is refocusing attention on the country’s troubled history with large dams.

At a public ceremony in March, Ethiopian Prime Minister Meles Zenawi laid the cornerstone for the new dam, a hydroelectric power plant that will span a section of the Blue Nile River in the country’s Benishangul-Gumuz region.

The Blue Nile originates in Ethiopia’s Lake Tana and is one of two major tributaries of the Nile, the world’s longest river.

When completed in 2015, the Grand Millennium Dam will be the largest hydroelectric power plant in Africa. It will also create the country's largest artificial lake, with a capacity of 63 billion cubic meters of water—twice the size of Lake Tana in Ethiopia’s Amhara region.

In late June, Ethiopia announced that it would build four additional dams on the Blue Nile that will work in conjunction with the Grand Millennium Dam to generate more than 15,000 megawatts of electricity.

The cost of the four new dams has not been disclosed, but the Grand Millennium Dam is estimated to cost about $4.7 billion.

Power Hub

Ethiopia has stated that it wants to become a major power hub for Africa by generating hydropower electricity that it can sell to its neighbors, and the country is in a unique position to succeed.

"They call Ethiopia the water tower of Africa," said climatologist Chris Funk of the University of California, Santa Barbara (UCSB). "If you look at an elevation map of the continent, it's all pretty low except for the Ethiopia highlands. So you have these big high mountains that get a ton of rainfall and so the potential for hydropower is pretty massive."

This potential has not been lost on the Ethiopian government. According to environmental group International Rivers, Ethiopia has more than 20 dams that are either currently operating or under construction–more than any other African nation.

Ethiopia's government says the bulk of the Nile dams' generated electricity will be exported to neighboring countries, but Egypt and Northern Sudan have expressed concern that the mega dam project could seriously reduce the downstream water flow of the Nile River in their countries.

Conservationists also are worried about the Grand Millennium Dam's environmental impacts. To date, no environmental impact assessment report, or EIA, for the project has been published and the country has not indicated that any studies are planned.

This isn't surprising, said International Rivers spokesperson Lori Pottinger.

An EIA report that Ethiopia released in 2009 for Gibe III—another large dam project on the country's Omo River that is currently under construction—was widely criticized as flawed and inadequate and led the World Bank, European Investment Bank, and the African Development Bank to pull out of the project in 2010.

Ethiopia may be seeking to avoid a similar public backlash with the Grand Millennium Dam, but the lack of an EIA report has made it difficult to raise international funds for the project, Pottinger said.

Troubled Waters

Ethiopia also has a troubled history of large dam projects that does not inspire confidence. The country’s dams have been linked to the controversial government practice of "land grabs."

The Ethiopian government, which owns all land in the country, has been pushing tribal people off their ancestral lands and is leasing large tracts of land to foreign interests, critics say.

"The government has already initiated extensive agricultural irrigation schemes . . . for private corporations and the government, forcing large numbers of the indigenous population out of these agricultural and livestock grazing lands," said Claudia Carr, a professor of international rural resource development at the University of California, Berkeley.

"Since they have nowhere to go for alternative survival, armed conflicts in the region are sharply rising,." Carr added.

According to a 2009 Africa Resources Working Group (ARWG) report, the Gibe III dam could reduce the level of Lake Turkana by as much as 66 feet (20 meters) and affect as many as half a million people living in Ethiopia and Kenya.

Such a drastic drop in water level would not only threaten wildlife in the region—including hippopotamus, crocodiles, and migrant waterfowl—but it would also increase the lake’s salinity because the salt concentration in the lake increases as the water level drops, Carr said.

"Lake Turkana is already just borderline potable for humans and livestock,” she added. “An increase in salinity would push conditions over this limit, as well as disrupt the entire biology of the lake itself.”

Charging Ahead

Despite its difficulty in soliciting foreign funds, the government of Ethiopia has said it is committed to the Grand Millennium Dam and that it plans to fund the project without foreign aid by selling bonds to the public.

“The Ethiopian population has agreed to build the Grand Millennium Dam. All workers are giving one month salary, traders are buying bonds, the diaspora is contributing to the dam,” Ethiopian government spokesperson Haji Ibsa Gendo told Bloomberg News earlier this year.

But even if the Grand Millennium and Gibe III dams are successfully completed, it's still unclear who will buy their electricity.

According to the Sudan Tribune, Ethiopia has "initial agreements" to export electricity to Sudan, Dijibouti, and Kenya. But dam critics say the majority of Africans are not connected to the power grid, and that Ethiopia will be generating far more electricity than it or its neighbors currently need.

"It's anyone's guess how they're going to sell off this electricity," Pottinger said.

News reports indicate that South Sudan could also be a potential buyer of Ethiopia’s electricity, but the situation is complicated by a 1929 agreement that gives Egypt and Sudan rights over all of the Nile’s water–an agreement that would now presumably include South Sudan and which Ethiopia and several other African nations are challenging.

“Currently Sudan has a relatively large chunk of rights to the Nile and it’s unclear how those are going to be divided, who they’re going to side with, and what they’re going to want from Ethiopia,” Pottinger said. “I don’t think anybody can guess what’s going to happen at this point.”

Climate Change

There is also a danger that some of Ethiopia's dams will become obsolete in a few decades as climate changes driven by global warming alter hydrological cycles across eastern Africa.

One set of climate analyses, by UCSB's Funk and his colleagues, predicts that southern Ethiopia could experience as much as a 20 percent decline in rainfall in the coming decades as a result of changing climate patterns. If this happens, it could threaten the electricity production of Gibe III and other dams on the Omo River.

"Whether you believe my analysis of why the rainfall is declining, certainly the observation suggests the decline is happening. You can be an unbeliever in climate change and still be concerned that the rainfall is going down," Funk said.

According to International River's Pottinger, no dams in Ethiopia are being analyzed for the potential impacts of climate change.

"This region of East Africa is already extremely dependent on hydropower," she said.