For 1,000 kilometers, from the first cataract of the Nile River in southern Egypt to the fourth cataract in Sudan, there are hundreds of stone walls. They appear in channels, on plains that are flooded a few times a year, or in river belts that are now dry.
These breakwaters are the first work of hydraulic engineering in history. Flood and flow control structures built 3,000 years ago by the ancient Egyptians in the Nile Valley and now in common use around the world.
Some were built to trap nutrient-rich stream sediments for agriculture, a practice still recorded as early as the early 19th century AD, indicating that these works were used for long periods of time.
As the researchers explain in an article published in the journal Geoarchaeology, the vast network of Nile "river groynes" predates by more than 2,500 years what until now were the oldest known examples in the world, those of the Yellow River in China.
"Using satellite images, drones and ground surveys, as well as historical sources, we located nearly 1,300 walls between the first cataract in southern Egypt and the fourth cataract in Sudan," Dr. Matthew Dalton of the University of Sudan said in a statement. from Western Australia and lead author of the study.
The international team mapped and recorded the remains for more than 1,100 kilometers to determine the time of construction, who built it and why. Hundreds of groynes are now submerged under the Aswan High Dam reservoir but were recorded in 19th-century traveler's journals, a 200-year-old map, and archives of aerial photographs, including some taken by the Royal Air Force. in 1934.
Still, many found themselves within the old Nile channels that had dried up due to climate change. Specialists used radiocarbon and luminescence dating techniques to establish that some were built more than 3,000 years ago.
"Radiometric dating suggests that this form of hydraulic engineering was first performed by indigenous Nubian communities, as well as by the inhabitants of cities established later by the New Kingdom pharaohs," the authors write.
Talking to farmers in what is now Sudanese Nubia, the researchers found that river breakwaters continued to be built even into the 1970s and that the land formed by some walls was still being cultivated today.
The team also identified much larger stone walls within the Nile, some up to five meters thick and 200 meters long, dams that would have directed the river's flow and aided boating through the treacherous rapids of the largest. river course of all Africa.
“These monumental river breakwaters helped connect the people of ancient Egypt and Nubia by facilitating the long-distance movement of resources, armies, people and ideas along the Nile,” concludes Dr. Dalton.
