How water power may be the secret behind the first pyramids

It is perhaps the oldest question in history: how exactly did the Egyptians build the pyramids? Archaeologists have puzzled over it for centuries, but now a new study of the earliest pyramid suggests that they might have used hydraulic power to build it up from within, “like a volcano”.
The striking theory, which has been published by French engineers, is based around a new assessment of a complicated water system at the Step Pyramid of Djoser, which was built in Saqqara, south of modern Cairo, 4,500 years ago.
The pyramid was built next to an ancient water treatment facility that was also used to purify water for human use. However, a section was found to function as a hydraulic system that could have worked like a lift in the centre of the pyramid structure, potentially helping in its construction.
Archaeologists discovered many of these structures 15 years ago, but their exact purpose has never been agreed upon. They form part of a necropolis complex designed by Imhotep, a pioneering architect who was himself later revered as a demigod, which was used since the period of the Old Kingdom of Egypt (2,700–2,200BC) as the last resting place of Egyptian royalty.
The latest research, led by Grenoble Alpes University, began by considering the Gisr el-Mudir, a stone enclosure west of the pyramid, which has variously been theorised to be a fortress, a cattle enclosure, an arena or another, unfinished pyramid. However, satellite photos showed that it would have been fed by the Abusir wadi, a seasonal stream that flowed from the mountains into the Nile.
The engineers recognised a system of “check dams” that were built to deal with flash floods, which would have been far more common in this period, when large parts of the Sahara were lush and green. This would have safely guided water into the basin of the Gisr el-Mudir, whose systems could allow sediment to drop and produce clear water. However, it had a second purpose.
One pipe from this artificial floodplain led to the site of the pyramid and even now emerges in the very centre of the pyramid, where there is a vertical shaft. This had previously been thought to be a burial chamber — human remains had been found — but, at 28 metres deep, it allowed space for workmen to place heavy stones into the shaft, which could then be filled with and drained of water to move stones, floated on rafts, up and down.
The theory says that the pyramid was then built in a “volcano” style, with stones coming out of this central shaft before the water was drained to re-set the system. It is likely that other, previously theorised methods such as ramps, sledges and levers were used in addition to this, but the hydraulic lift would have saved a lot of time and effort.
“Ancient Egyptians are famous for their pioneering and mastery of hydraulics through canals for irrigation purposes and barges to transport huge stones,” the study, released online before publication in the journal PLOS One, says. “This work opens a new line of research: the use of hydraulic force to erect the massive structures built by pharaohs.”