Scientists find traces of a lost river next to the pyramids

Why were more than two dozen of ancient Egypt’s pyramids — including the Great Pyramid of Giza — clustered in a narrow strip of desert? Scientists say they’ve come up with a solution to the mystery: Thousands of years ago, a river ran through it.

The research team, led by Eman Ghoneim of the University of North Carolina at Wilmington, identified the extinct riverbed with ground-penetrating radar and some geological sifting and sleuthing. They call this dried-up branch of the Nile “the Ahramat Branch” — a name derived from the Arabic word for pyramid.

Confirming the existence of the Ahramat Branch could resolve some of the questions relating to how ancient Egyptians were able to accomplish the monumental task of building the pyramids.

“Many of the pyramids, dating to the Old and Middle Kingdoms, have causeways that lead to the branch and terminate with Valley Temples which may have acted as river harbors along it in the past,” the researchers write in a paper published today in the journal Communications Earth & Environment.

“We suggest that the Ahramat Branch played a role in the monuments’ construction and that it was simultaneously active and used as a transportation waterway for workmen and building materials to the pyramids’ sites,” they say.

The idea that river channels once came close to pyramid construction sites isn’t exactly new. Two years ago, a different team of researchers published evidence that a now-defunct river channel dubbed the Khufu Branch was used to facilitate construction of the Great Pyramid during the reign of Pharaoh Khufu, more than 4,500 years ago. Their conclusion was based on an analysis of sediment cores that contained pollen grains associated with aquatic plants.

That discovery explained why the pyramids at Giza were placed where they were: The Khufu Branch offered a relatively easy route for transporting two-ton blocks of limestone and granite to the construction site on barges. But by itself, the earlier finding didn’t address why other groupings of pyramids, extending dozens of miles southward, were also built in what are now desert surroundings.

Ghoneim and her colleagues expanded the search for dried-up riverbeds by analyzing synthetic aperture radar readings, multispectral imaging data and topographical data acquired by satellites. Their analysis guided a campaign of core sampling that documented how riverbeds filled up with mud and sand over the course of centuries.

The researchers determined that in ancient times, the Ahramat Branch extended for about 40 miles (64 kilometers) from the pyramids at Lisht to Giza, flowing past 31 pyramids in all. The branch and its associated inlets served as links to the Saqqara necropolis and to the Dahshur necropolis, which is the site of the Bent Pyramid and the Red Pyramid.

The river channel was situated between 1.5 and 6.5 miles (2.5 to 10.25 kilometers) west of the modern Nile River. Its waters were 6 to 26 feet (2 to 8 meters) in depth — deep enough to be navigable — and the width ranged from 650 feet to nearly a half-mile (200 to 700 meters).

“Our research offers the first map of one of the main ancient
branches of the Nile at such a large scale and links it with the largest pyramid fields of Egypt,” Ghoneim said in a news release.

Shipments could have been brought up from the river channel to the pyramid complexes via ceremonial causeways.

“In the study area, it was found that many of the causeways of the pyramids run perpendicular to the course of the Ahramat Branch and terminate directly on its riverbank,” the researchers say. “In Egyptian pyramid complexes, the valley temples at the end of causeways acted as river harbors. These harbors served as an entry point for the river borne visitors and ceremonial roads to the pyramid.”

Why did the Ahramat Branch dry up? During the heyday of pyramid construction, the Nile Valley was in the midst of a climatic transition. An era known as the African Humid Period was ending, rainfall was declining, and the Nile’s secondary channels were shrinking.

“The main course of the Nile River laterally migrated, and its peripheral branches silted up, leaving behind many ancient Egyptian sites distant from the present-day river course,” the researchers say. Tectonic activity could have contributed to the Nile’s eastward shift — and to the Ahramat Branch’s disappearance.

The newly published research demonstrates how ground-penetrating radar and other high-tech sensing tools can produce new insights about Egypt’s past — and perhaps guide plans for Egypt’s future.

“Revealing this extinct Nile branch can provide a more refined idea of where ancient settlements were possibly located in relation to it and prevent them from being lost to rapid urbanization,” the researchers write. “This could improve the protection measures of Egyptian cultural heritage. It is the hope that our findings can improve conservation measures and raise awareness of these sites for modern development planning.”

In addition to Ghoneim, authors of the paper published by Communications Earth & Environment, titled “The Egyptian Pyramid Chain Was Built Along the Now Abandoned Ahramat Nile Branch,” include Timothy J. Ralph, Suzanne Onstine, Raghda El-Behaedi, Gad El-Qady, Amr S. Fahil, Mahfooz Hafez, Magdy Atya, Mohamed Ebrahim, Ashraf Khozym and Mohamed S. Fathy. The work was funded by a grant from the National Science Foundation.