From its source to sea, Nile is in dangerous threat

Climate change, pollution and exploitation by man are putting existential pressure on the world's second longest river, on which half a billion people depend for survival.

All along its 6,500-kilometre (4,000-mile) length, alarm bells are ringing.

At its mouth on the Mediterranean, Sayed Mohammed is watching Egypt's fertile Nile Delta disappear. In Sudan, fellow farmer Mohammed Jomaa fears for his harvests, while at its threatened source in Uganda, there is less and less hydroelectric power for Christine Nalwadda Kalema to light her mud and wattle home.

"The Nile is the most important thing for us," said Jomaa, who at 17 is the latest generation of his family to work the river's rich banks at Alty in Gezira state.

"We certainly do not wish for anything to change," he said.

But the Nile is no longer the unperturbable river of myth. In half a century its flow has dropped from 3,000 cubic metres (10,600 cubic feet) per second to 2,830 cubic metres.

Yet it could get much, much worse. With multiple droughts in east Africa, its flow could fall by 70 percent, according to the United Nations' most dire predictions.

Every year for the past six decades, the Mediterranean has eaten away between 35 and 75 metres (38-82 yards) of the Nile Delta. If the sea level rises even by a metre, a third of this intensely fertile region could disappear, the UN fears, forcing nine million people from their homes.

What was once a bread basket has become the third most vulnerable place on the planet to climate change.

Lake Victoria, the Nile's biggest source of water after rainfall, could also dry up due to drought, evaporation and slow tilts in the Earth's axis.

With such grim scenarios in store, governments have scrambled to capture its flow. But experts say dams are only hastening the coming catastrophe.