A picture taken on May 28, 2013 shows the Blue Nile in Guba, Ethiopia, during its diversion ceremony. Ethiopia has begun diverting the Blue Nile as part of a giant dam project, officials said on May 29, 2013 risking potential unease from downstream nations Sudan and Egypt. The $4.2 billion (3.2 billion euro) Grand Renaissance Dam hydroelectric project had to divert a short section of the river -- one of two major tributaries to the main Nile -- to allow the main dam wall to be built. "To build the dam, the natural course must be dry," said Addis Tadele, spokesman for the Ethiopian Electric Power Corporation (EEPCo), a day after a formal ceremony at the construction site. AFP PHOTO / WILLIAM LLOYD GEORGE (Photo credit should read William Lloyd-George/AFP/Getty Images)