An independent panel of experts reported Sunday Ethiopia's $4.7 billion Grand Renaissance Dam on the Blue Nile will not significantly affect Egypt and neighboring Sudan.
But that does not seem to have pacified the Egyptians who under a 1929 colonial-era agreement get the lion's share of the Nile's flow of 85 billion cubic meters a year and refuses to surrender any of it.
The Ethiopians' massive hydroelectric dam, 20 percent built, would reportedly cut that by 18 billion cubic meters annually, which Cairo says is well below the minimum it needs for its 82 million people.
Ethiopia began diverting the Blue Nile May 29 to allow the main dam wall of the planned 6,000 megawatt hydroelectric project to be built.
That caused consternation and anger in Cairo about the long-term threat to irrigation and electricity supplies.
At a meeting Monday of Egyptian political leaders hosted by President Mohamed Morsi, several politicians, unaware the gathering was being televised live called for hostile action against Addis Ababa, including sabotage and attacks by local insurgents.
Younis Makhyoun, leader of an ultra-conservative Islamist party, urged the government to retaliate by supporting Ethiopian rebels, or as a last resort, "using the intelligence service to destroy the dam."
This is just the latest chapter in a long confrontation over the Nile between Cairo, backed by neighboring Sudan, and Ethiopia and several other upstream African states over sharing the Nile's waters.
Ethiopia is particularly proprietorial since the Blue Nile, a major tributary of the world's longest river, starts in the Ethiopian highlands.
In the Arab world, where conspiracy theorists thrive, many see the Ethiopian action as an African plot against the Arabs.
In February, Saudi Arabia's deputy defense minister, Prince Khaled bin Sultan, declared Riyadh takes a dim view of Ethiopia's ambitious dam-building on the Nile.
He accused Addis Ababa of seeking to harm Arabs, and ventured: "There are fingers messing with the water resources of Egypt and Sudan which are rooted in the mind and body of Ethiopia. They do not miss an opportunity to harm Arabs."
There has been no shortage of accusations of subterfuge and intrigue by both camps.
In November 2010, the late Ethiopian dictator Meles Zenawi boasted he would swiftly vanquish any attempts by Cairo to use military force.
"I'm not worried that the Egyptians will suddenly invade Ethiopia. Nobody who has tried that has lived to tell the story."
In August 2012, WiliLeaks quoted an alleged 2010 internal email from the U.S. global security consultancy Stratfor in which an unidentified "high-level Egyptian security/intel source in regular direct contact with" then President Hosni Mubarak and his late intelligence chief, Gen. Omar Suleiman, spelled out Cairo's military options.
"If it comes to a crisis," the source wrote, "we will send a jet to bomb the dam and come back in one day, simple as that.
"Or we can send out Special Forces to block/sabotage the dam. Look back at an operation Egypt did in the mid-late 1970s, I think 1976, when Ethiopia was trying to build a large dam.
"We blew up the equipment while it was traveling by sea to Ethiopia. A useful case study."
Another reported plan by Egypt was coordinating with southern neighbor Sudan, which would also be affected by the Ethiopian dam, to build a military base in its territory from which to bomb the Grand Renaissance and other Ethiopian dams.
The secret base, according to other sources, would be located at Kursi in the western Darfur region.
The dictatorial Meles is reported to have drawn up plans to attack Egypt's Soviet-built Aswan Dam on the Nile, believing a regional version of the Cold War's threat of mutual assured destruction would prevent open warfare.
In May, there were media reports the Ethiopian regime had released insurgent prisoners from the Benshangul People's Liberation Movement which operates out of Sudan, as part of a peace process aimed at protecting the Grand Renaissance Dam from attack.
The guerrillas had earlier threatened to attack the dam, which is near the Sudanese border.