The diversion of a major Nile tributary has sparked tensions between Egypt and Ethiopia, even as Ethiopia continues construction of Africa’s biggest dam, the Grand Ethiopian Renaissance Dam, on the world’s longest river.

On Tuesday, Ethiopia diverted the course of the Blue Nile to commence construction of the dam, but government officials said the reservoir would be filled gradually to minimize the effects on lower-riparian nations.

The 6000 megawatt, $4.3 billion hydropower project has courted controversy since it was first announced in March 2011. Ethiopia is the source of the Blue Nile, a major tributary that joins the White Nile in Sudan and accounts for nearly 60 per cent of Nile water.

Ethiopia’s move to control the flow of the Blue Nile has unsettled Egypt, which relies on the river for almost all its fresh water needs and consumes two-thirds of the water under a colonial treaty first signed in 1929. The treaty divides the water between Sudan and Egypt – once prized British colonies – and ignores the claims of eight other Nilotic nations.

Ethiopian officials expect the dam to begin producing electricity as early as next year and hope to complete construction by 2017. Once complete, the dam shall stand at the head of a 74 billion cubic metre reservoir, the filling of which is expected to severely disrupt downstream flows to Egypt and Sudan.

“We are not selfish, we are not only looking at our national interest,” said Ethiopian Deputy Prime Minister and Chairman of the state-owned Ethiopian Electric Power Corporation in an interview with Bloomberg. “This is an international river and we will try our best to accommodate their benefits and interests.”

In the past, Egypt has threatened to go to war to protect its water interests, but the current administration sounded a more conciliatory note. “A military solution for the Nile River Crisis is ruled out,” said Egypt’s Irrigation and Water Resources Minister, Mohammed Baheddin at a press conference in Cairo on Thursday, according to the Associated Press.

On Wednesday, State media reported that Sudan’s Minister for Water Resources, Osama Abdullah Al-Hassan, flew to Cairo to discuss the implications of the dam-construction for Egypt and Sudan. On Sunday, a tripartite team of Egyptian, Ethiopian and Sudanese technical experts are expected to submit a report on the dam.

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