Cairo was notified in advance about the diversion of the Blue Nile before the move was officially announced by Ethiopia late Monday evening, an informed government official told Ahram Online.
"We had already known this; we were notified and the president knew," he said.
Ethiopia on Tuesday began diverting the course of the Blue Nile, one of the Nile River’s two major tributaries, as part of a project to build a new dam.
The move, called "historic" by Ethiopian government spokesman Bereket Simon, is likely to anger downstream Egypt and Sudan, both of which fear the move will negatively affect their annual quotas on Nile water.
Ethiopia's 'Renaissance Dam' is one of four dams planned for construction along the Blue Nile, which provides Egypt with the lion's share of its annual 55 billion cubic metres of Nile water.
On Monday, Ethiopian Foreign Minister Gebre-Christos said the dam, which is currently under construction and will be able to store some 84 million cubic metres of Nile water, would be used exclusively for power generation and would not reduce Egypt's share of Nile water.
The Egyptian government source said that, during President Mohamed Morsi's visit to Addis Ababa – which ended Monday evening only hours before the announcement – there had been unsuccessful attempts to convince the Ethiopian side to delay the move.
"There were attempts [to persuade Ethiopia to postpone the move] through several diplomatic channels, both direct and indirect, and during the president's talks with senior Ethiopian officials," the source said.
"President Morsi raised the matter, but it was clear Ethiopia is determined to go ahead."
The source added that Addis Ababa was offering "reassurances" that it would be "sensitive" to Egyptian concerns and would "try to accommodate" Cairo's demand that it fill the planned dam's reservoir only gradually, so as to ensure that the effect on Egypt's annual share of Nile water would not be too abrupt.
The Ethiopian move to redirect the course of the Blue Nile is perceived by Cairo as an indication of Addis Ababa's determination to follow through with its plans, despite Egypt’s objections that such plans violate international agreements that put Egypt’s annual share of Nile water at 55 billion cubic metres.
Addis Ababa has repeatedly shrugged off these agreements, asserting that they deny all Nile Basin states – apart from Egypt and Sudan – any serious share of river water.
Since 1902, there have been over ten agreements regulating the distribution of Nile water, including a 1959 agreement that specified Egypt's exact share.
Most of these agreements stipulate that no dams or other irrigation projects should be built on the Nile without the prior notification of all Nile Basin states.
It is a precondition consistent with international law and with regulations adopted by the basin states of other rivers.
In 1999, Egypt agreed to join the other Nile Basin countries in a negotiation process specifically aimed at addressing the demands of the upstream countries.
During the process, Egypt issued two recommendations: firstly, to reduce water wastage, currently estimated at millions of cubic metres (some studies indicate that total wastage is more than Egypt's entire annual share); and, secondly, to streamline usage of upstream water resources, including rainwater.
In 2010, both Egypt and Sudan (before the latter was split in two) suspended their participation in the talks due to a failure to define the terms of an agreement governing the construction of irrigation projects on the Nile.
The fate of this process remains in limbo, however, with both Cairo and Khartoum insisting on the full consensus of all basin countries before any dams can be built on the river.
The dispute over Nile water began in 2009 with demands made by upstream states, including Ethiopia, to reduce Egypt's share in line with a new water-sharing treaty already signed by most upstream states.
Egypt is already suffering a water shortage and there are genuine concerns that Ethiopia's planned Renaissance Dam would aggravate an existing problem that has until now been poorly attended to.
According to Egypt's National Planning Institute, the country will likely need an additional 21 billion cubic metres of water per year by 2050 – on top of its current 55-billion-metre quota – to meet the water needs of a projected population of 150 million.
A source from the UN Development Programme suggested that Egypt's annual loss of water – due to outdated irrigation systems and poor sewage maintenance – currently stood at some 10 percent of its official annual share.
"The fact that Egyptian authorities have turned a blind eye to the loss of fertile land is an added problem, as this means that Egypt would need much more water to help with desert land reclamation," the source said.
Egypt's concerns go beyond its share of Nile water.
A source close to the three-way consultation mechanism bringing together Egypt, Sudan and Ethiopia to discuss "technical aspects and influences" of Ethiopia's planned Renaissance Dam speaks of "safety concerns" as well.
"I'm not saying the Renaissance Dam will collapse shortly after its construction, but I'm saying there are concerns that – in a few years – it could develop cracks," he said.
The three-way consultation, which has been ongoing for over a year, began its sixth session in Addis Ababa two days ago.
It should issue a comprehensive report on the issue by the end of this month or early next month.