So what happens now? Might the Nile’s sorry state one day lead to war?
By the time the river reaches Cairo, it is utterly filthy.
The banks are laced with rubbish, and the water is gloopy and often gleaming with toxins. Already, farmers are complaining of water shortages in the northern Delta, as the Nile’s increasingly meagre flow struggles to filter through clogged-up irrigation canals.
To officials staring out from Cairo’s riverside ministries, it is a grim, in-your-face illustration of their country’s precarious water future. “The Nile is everything to us - what we drink, what we eat,” said Ali Menoufi, from the Ministry of Water Resources. “It would be a disaster if anything happened to it.”
The rhetoric and tenor of Nile basin relations over the past few years have reflected the high stakes.
A politician in a previous Egyptian administration called for a strike on Ethiopia’s prized dam in 2013, while state-owned media in Addis Ababa has not been shy about ratcheting up tensions in response.
As GERD has neared completion, authorities in Cairo have bolstered their strategic capabilities, acquiring two French Mistral long range-strike battleships in a move that analysts believe is at least partly calculated to send a message to their southern rival.
“All options are on the table,” said Ahmed Abu Zeid, the foreign ministry spokesman and a former Nile talks negotiator, when asked whether military action remains an option.
History suggests that the Nile basin states are unlikely to come to blows over the river any time soon. Transboundary water disputes have a strong record of peaceful resolution, and there are indications that Egypt is reconciling itself to the dam’s inevitability.
However, Ethiopia’s intense secretiveness over GERD’s ramifications remains a stumbling block, as do the negotiations over how long it will take to fill the dam’s enormous reservoir.
And the war of words continues to play out in some unsavoury ways.
Ethiopian Oromo refugees in Egypt report increased harassment whenever GERD hits the news. Some Ethiopian monasteries, including Lake Tana’s island churches, which have traditionally enjoyed close ties with their Coptic Orthodox brethren, have broken off relations, sending Egyptian monks home.
At a time when Sudan is leasing millions of acres of arable Nile-side land to Gulf Arab agribusinesses – at least 2.5 million to the UAE, there are myriad potential banana skins on the road ahead.
“If you think about it. We’re growing and the river’s not,” said Gebremichael Mengistu, an Ethiopian university student I met in Bahir Dar, ably summing up the source of the tension. “It was always going to come to this.”
But there is still enough river for a fittingly bleak end.
For the fishermen who ply their trade around Rosetta, where the western branch seeps into the Mediterranean, the Nile’s shabby state has proven particularly disastrous.
Much of their river catch has died off, and what they do hook looks so unpalatable that they usually won’t eat it. The Nile’s final stretch is so poisonous that even out on the open sea, around the river mouth, few species can survive, fishermen say.
“We worshipped the river, but now we want nothing to do with it,” said Khamees Khalla, untangling his nets steps from the fort where the Rosetta Stone, the key to deciphering hieroglyphics, was found. “We all have the same tactic - get as far away from the river as possible.”
Battered by challenging fishing conditions – and by increased competition as many beleaguered coastal farmers try their hand at sea – some trawlermen have turned to crime.
Twice, Mohammed, a Rosetta-based fisherman, has ferried migrants and refugees part of the way to Europe, and twice he has almost been caught. But with the river no longer the cash cow it once was and people from other struggling parts of the Nile basin willing to pay much more than he earns fishing for safe passage, he insists he is not deterred.
“I would prefer to make my living from the Nile, like my father, like my father’s father, but that’s just not possible any more,” he said.
This article was made possible by funding from the Pulitzer Center for Crisis Reporting.