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Death of the Nile?
Original source: Down to Earth
Death of the Nile? Mega dams have killed the river’s ability to flush carcinogens, slowly killing its delta
Much of the contamination by heavy metals is irreversible, but science-based conservation measures could help, study claims
Large-scale pollution from untreated agricultural drainage and wastewater is putting existential pressure on the delta system of the world’s longest river, according to a new study.
Pollution, coastal erosion and seawater intrusion challenge the sustainability of the delta, on which the population of Egypt rely for food security, noted the document published in the journal Earth’s Future on March 7, 2023.
In this study, the researchers evaluated the levels of heavy metal pollution along the two delta branches of the iconic river to identify their sources and explore the implications of damming on heavy metal concentration.
The current levels of pollution also endanger millions of migratory birds that use the area as a stopover during their journey along the east African flyway, the researchers wrote.
They arrived at this conclusion after analysing eight heavy metals — lead, chromium, cadmium, copper, zinc, iron, manganese and nickel — present in samples of sediment collected from the bottom of two branches of the river’s delta.
These samples were highly polluted, especially by toxic heavy metals such as cadmium, nickel, chromium, copper, lead and zinc.
The high concentrations of cadmium, chromium, copper, lead, nickel and zinc are carcinogenic and can adversely affect plant and human health. They can drastically harm plant growth, causing necrosis and chlorosis in leaves and death of the plant as well.
Lead can adversely impact human circulatory and cardiovascular systems, while chromium, copper, nickel and cadmium can affect renal and kidney functions.
The Nile brings together 11 riparian countries — the Democratic Republic of the Congo, Burundi, Uganda, Kenya, South Sudan, Ethiopia, Eritrea, Rwanda, Tanzania, Sudan and Egypt.
Egypt, the aridest country downstream of the Nile, is undergoing one of its highest water budget deficits. This deficit is compensated by the intensive reuse of wastewater in the Nile delta, the consequences of which have been understudied until now, the researchers revealed.
In the absence of proper treatment of recycled water, concentrations of heavy metals may increase and get permanently embedded in the riverbed.
Mega-dams built upstream disrupt the river’s natural flow; sediments thus accumulated adversely affect its ability to flush contaminants out into the Mediterranean Sea, leaving toxins to build up in bottom sediment over time.
Alarmingly, much of this contamination by heavy metals is irreversible. However, the study claimed that science-based conservation measures could alleviate environmental degradation and restore the Nile delta’s ecosystem to relatively healthy levels.
The researchers underscored the need for more research on the environmental impacts of using untreated water and the change in river turbidity under increased upstream damming.
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