By Xan Rice, Guardian
At the foot of a towering gorge slicing through southern Ethiopia, the Omo river suddenly disappears into a tunnel bored into the rock face. Excavators claw at the soil and stone in the exposed riverbed beyond, where a giant concrete wall will soon appear in the ravine.
At 243 meters, the Gibe III dam will be the highest on the continent, a controversial centerpiece of Ethiopia's extraordinary multibillion-pound hydroelectric boom.
The country that prides itself as "The Water Tower of Africa" plans to end an energy shortage by building a network of mega dams on the web of rivers that tumble down from its highlands.
By 2020, with the help of Italian and Chinese construction firms, Ethiopia will, it hopes, have increased its power generation capacity 15-fold and become a significant exporter of electricity to the region.
"For a developing country like ours the dams are a must," said Abdulhakim Mohammed, head of generation construction at the Ethiopia Electric Power Corporation (Eepco). "Power is everything."
But the pace and scale of the hydro projects have alarmed environmental groups, who say proper impact assessment studies are not being carried out.
Gibe III, which will have a generating capacity of 1,870MW — double what was available in all of Ethiopia last year — has sparked the greatest opposition.
This week a coalition of campaign groups, including International Rivers, based in California, and Survival International, launched an online petition with the aim of stopping the dam, warning of potentially disastrous social and economic effects for tribes downstream.
"It's an unnecessary, highly destructive project," said Terri Hathaway, Africa campaigner for International Rivers.
Nobody disputes the urgent need for additional electrical power in Ethiopia. In rural areas, where the bulk of the 80 million Ethiopians live, only 2% of households get access to electricity and the capital, Addis Ababa, has been hit by blackouts.
Meanwhile, a fast-growing economy and high population growth has caused the demand for electricity to rise by 25% each year, according to Eepco.
The country's topography makes hydropower an obvious solution. Lake Tana, in Ethiopia, is the source of and provides 85% of the water for, the Blue Nile, one of the two main tributaries of the Nile. The country also has another dozen large river basins. By some estimates, due to the volume of water cascading to the lowlands, the country has got the potential to generate 45,000MW of hydropower, putting it second in Africa only to the Democratic Republic of Congo.
While Ethiopia has approved plans for several new hydro schemes in the coming years, including a giant 2,100MW project on the Blue Nile, which will also serve Sudan and Egypt, a number of dams have already been built, or are almost complete. The 93-mile long reservoir created by Gibe III will stretch to the tail of the 420MW Gibe II power project, which was opened in January by the Italian construction company Salini.
Further north, Salini is also constructing a power plant near Lake Tana, while Sinohydro, the Chinese firm that helped build the famous Three Gorges Dam, has just completed another.
The dam-building frenzy is about much more than simply lighting up Ethiopia's homes. For some, it is about viewing the country's rivers in the same way as other nations view their oil or mineral wealth: a valuable source of foreign currency.
In the next few years Ethiopia plans to start transmitting power to its neighbors. The construction of transmission lines to Djibouti and Sudan has begun, and a supply agreement has been reached with Kenya. If all goes well, electricity could become Ethiopia's most valuable export.