The waters behind Ethiopia's huge multibillion-dollar dam on the Blue Nile are rising.
The moment has been 10 years in the making and while the Ethiopian government says it plans to start filling the reservoir this month, it denies that comments on Wednesday night by Water Minister Seleshi Bekele were an official declaration.
Sudan, 32 kilometres downriver from the Grand Ethiopian Renaissance Dam, says that the river's flow is down by about 90 million cubic metres of water a day, about a fifth of the average flow in August, and that the dam's gates are shut.
Egypt has demanded clarity from Addis Ababa.
The issue has inflamed nationalist sentiment and led to warnings of existential effects and possible military action.
But analysts and officials all say that the first trapping of water is unlikely to leave anyone down river short.
What’s at stake?
Ultimately, the long-running dispute is about the rules that should govern such a massive dam project.
Egypt, which relies on the Nile for more than 90 per cent of the water needed by its 100 million people, wants to know exactly how much water Ethiopia will let through the sluice gates each year.
It wants agreement on what happens if there is a long drought, and who will arbitrate on any dispute between the three countries.
Egypt says Ethiopia has not factored in the risk of a major drought, like the ones that affected the Nile Basin in the late 1970s and early 1980s.
Although it agrees it is unlikely, Egypt says such a situation would knock $1.8 billion (Dh6.61bn) from its economic production and lead to a million job losses a year.
So it wants Ethiopia to guarantee it 40 billion cubic metres a year after the first stage is completed.
Sudan wants to be sure that management of the dam will be effective and that it will never overflow, break or leak, causing massive flooding and devastation to its immediate neighbour.
It also wants to know it will not run low on water.
Ethiopia, with a population of more than 100 million people, accuses Egypt of a colonial-era attempt to control the Nile’s water.
It also questions why it should agree on a comprehensive framework to resolve every possible issue now when it is impossible to say what the effect of seasonal variation or climate change will be, or what further development upstream might do to water levels.
Addis Ababa says it is better to have a flexible arrangement that is equitable. But it says Egypt’s demand for an annual 40 billion cubic metres is unrealistic.
Why is first filling a watershed moment?
If Wednesday’s move was the start of the first filling, it is a major milestone.
"This act of the first filling has been turned into a very pivotal moment," William Davison, a senior analyst based in Ethiopia for Crisis Group, tells The National.
“Egypt says that there will be no more negotiation after first filling. Sudan opposes first filling without an agreement.”
Mr Davison says Ethiopia regards first filling as an extension of the dam's construction. Mr Bekele said on Wednesday that the two "go hand in hand".
While it is a major political moment, in terms of the water resources it will not make a huge difference.
“In terms of the hydrology, there is no chance of a serious water shortage occurring as a result of the act of first filling, especially in the first year when there is only a relatively small amount of water that Ethiopia will impound,” Mr Davison says.
So why is it so significant? Cairo says it sets a dangerous precedent if no deal is agreed to and that it will have repercussions later as Ethiopia has discussed more dams and projects upstream.
The threat of war
The idea of a water war may seem like something lifted from a disaster movie but Egypt will not take the threat of military action off the table.
And Ethiopia has taken the risk seriously, posting large numbers of soldiers and defence systems near the dam in recent years.
While analysts admit it is a possibility, they say no side really wants to get to that point and there is no international appetite for a devastating conflict in Africa.
“So while conflict doesn't seem to make sense, we do have some of the ingredients for it and there are certainly concerns about increased regional instability,” Mr Davison says.
“Really, the only way that the downstream interests can be secured here is by coming to a co-operative agreement or arrangement with Ethiopia.”
For now, there is no indication that talks are off and while the latest round again ended this week with no deal, more mediation from South Africa is in the pipeline.