The Nile is at the centre of geopolitical rivalry in the region.
At its heart is Egypt, where suspicions about former enemies and tensions with an age-old civilisation reveal deep-seated fears about water scarcity and losing control of the river.
"By the time Mohamed Ali began to rule Egypt in 1805, many threats had been made by the Ethiopian emperors to stop the water reaching Egypt. Most were just empty threats - but some were valid. Every time there was a new ruler in Egypt, they would threaten him and blackmail him so that he paid gold to the Ethiopian emperor," says Abdul-Moneam Gemaey, an Egyptian historian.
These fears have made Egypt suspicious about reported plans to divert the Nile to a former enemy.
"Egypt will not be able to stop Ethiopia from building dams on the Nile. That is history ... and that will not be part of the solution .... Ethiopia is able and willing to use its own resources to build dams on the Nile .... The way forward is to seek a win-win solution through diplomatic efforts ... not for Egypt to try and stop the un-stoppable," said Meles Zenawi, the late Ethiopian prime minister.
And they have led it into a tense stand-off with another country - an upstream state with the potential to dramatically affect the amount of water reaching Egypt.
The final episode of the three-part Struggle Over the Nile series explores the impact of Egypt's geopolitical rivalry with Israel and Ethiopia on the Nile.
"Historically, the most important relationships Israel built on the African continent were with Uganda, Ethiopia and Kenya. And it is no coincidence that all of them are upstream countries where the Nile originates. They did build relationships with other countries. But the River Nile was the major factor behind the formation of Israeli policy and strategy, says Helmy Moussa, Israeli affairs expert.
Source: Al Jazeera