The iconic Nile River Delta faces existential threats, according to a new study

Large-scale heavy metal pollution, coastal erosion, and seawater intrusion pose an existential threat to the Nile River Delta and endanger Egypt’s 60 million people (about twice the population of Texas) who depend on the resource of every aspect of life, according to new research from the USC Viterbi School of Engineering. In addition, the Nile River Delta is a critical stopover for migratory birds during their journey along the East African flyway.

The study, led by Essam Heggy of the USC Viterbi Innovation Fund Arid Climates and Water Research Center, was published Tuesday, March 7, in the journal The Future of Earth.

The impact of the pollution is particularly acute in Egypt, the most densely populated and arid nation downstream of the Nile, which is entirely dependent on the river as its sole source of water for drinking and crop irrigation. The country currently faces one of the highest water budget deficits in Africa after decades of compensating for dwindling water supplies with intensive, large-scale wastewater reuse, the consequences of which have not been adequately studied until now.

“You have roughly the combined populations of California and Florida living in an area the size of the state of New Jersey that is increasingly contaminated by toxic heavy metals,” Hegy said. “Today, the civilization that flourished in a picturesque waterscape for more than 7,000 years must face the reality of this irreversible large-scale environmental degradation.”

For the study, researchers from the US and Egypt analyzed the grain size and pollution levels of eight heavy metals in bottom sediment samples collected from two branches of the Nile River Delta. Key findings included:

• The sediments at the bottom of the Nile River are highly contaminated with heavy metals such as cadmium, nickel, chromium, copper, lead and zinc.

• Pollutants mainly come from untreated agricultural sewage and municipal and industrial sewage. Without proper treatment of recycled water, heavy metal concentrations increase and become permanently embedded in the river bed unlike organic pollutants that naturally degrade over time.

• Heavy metal concentrations could be exacerbated by increased damming of the Nile. Large dams built upstream disrupt the river’s natural flow and sediment flow and thus negatively affect its ability to flush pollutants into the Mediterranean Sea, allowing toxins to build up in the bottom sediment over time.

Much of the heavy metal contamination is irreversible, the researchers said, but scientific conservation measures suggested by the study can slow environmental degradation and hopefully restore the Nile River Delta ecosystem.

“Deteriorating water stress and rapid population growth in Egypt, past 100 million, have put local authorities in a quandary over whether to provide sufficient fresh water to the thirsty agricultural sector to ensure food supplies through the reuse of untreated agricultural drainage water or maintain the health of the Nile River,” said Abotalib Z. Abotalib, a postdoctoral researcher at USC Viterbi and co-author of the study. “The balance is challenging and the consequences of both choices are measurable.”

“Our study highlights the need for more research on the environmental impacts of untreated water recycling and the change in river turbidity under increased upstream Nile damming,” Heggy said.

“Continuing research with more sampling campaigns in this area could inform future conversations and collaborations between Nile River Basin nations who share a common interest in maintaining a healthy Nile River system.”