The step pyramid in the Saqqara necropolis, built for the ancient Egyptian pharaoh Djoser, is the oldest of the seven great pyramids in Egypt. However, the methods used to build it are still unknown. Now a research team has discovered evidence of a complex water system that may have helped in the construction of the 63-meter-high pyramid. Several basins and channels channeled water into the base of the pyramid, where it then fed a kind of elevator. This was then used to lift the large stone blocks upwards.
The necropolis of Saqqara is one of the largest and longest-used necropolises in ancient Egypt. Kings and dignitaries were buried here in tombs and pyramids around 5,000 years ago. The largest and oldest of these pyramids is the step pyramid of Pharaoh Djoser, built around 2650 BC. The almost 63-meter-high structure, constructed from around 2.3 million limestone blocks, is still considered a milestone in ancient Egyptian monumental architecture. However, as with the other pyramids, the methods used by the ancient Egyptian builders to lift the heavy stone blocks to such heights are controversial. “There is currently no generally accepted holistic model for pyramid construction,” explain Xavier Landreau from the Paleotechnical Institute in Paris and his colleagues. It is generally assumed that the stones were hoisted up using ramps, rollers or pulleys.
Water management system with basins, ditches and channels
To learn more about the context of the Djoser pyramid and the buildings surrounding it, Landreau and his team analyzed the area around Saqqara in more detail. The focus was on landscape forms and structures that could indicate a possible Egyptian water system – similar to the one the Maya later used for their cities and temples. It was already known that the Djoser pyramid stands near a now dried-up riverbed, the Abusir Wadi. “In order to investigate the connection between the Abusir Wadi and the construction of the step pyramid, we also mapped the catchment area west of Saqqara for the first time,” the team reports.
This revealed several previously unrecognized basins and channels through which water from the periodic rainfall of the time was channeled into the Abusir wadi and to the end of this dry valley. There are the remains of a rectangular structure surrounded by ramparts, the Gisr el-Mudir, measuring around 360 by 620 meters. This complex, located a few hundred meters west of the Djoser pyramid, is considered to be the oldest structure made of carved stone in Egypt, but its function was previously unknown. Landreau and his colleagues now conclude from the location and shape of Gisr el-Mudir that it was also part of the water system: “Its western wall probably served as the first dam for the inflow of water from the Abusir wadi,” they explain. From this basin, the water could then have been channeled into a ditch that surrounded the Djoser complex.
A hydraulic lifting device?
In the southern part of this trench, excavations uncovered another channel some time ago, around 27 meters deep. “This deep channel connects at least three underground caverns, the walls of which are precisely cut out of the rock and from which a tunnel leads,” report Landreau and his team. “The perfect geometric alignment of these caverns parallel to the Djoser pyramid is remarkable.” The floor of these caverns and the bottom of the two main shafts of the Djoser pyramid were at the same level. Both shafts were also connected by a 200 meter long pipe.
According to Landreau and his colleagues, this system suggests that water from the Abusir Wadi was once channeled through the trench and caverns into the substructure of the pyramid. This inflow of water could then have served as a drive for a hydraulic lifting system in the shafts, they suspect. The water level in the main shafts could probably be regulated by a system of heavy “plugs” hanging from cable winches. When the water in the shaft rose, it could lift a raft floating on the water with the stones needed for construction to a height of 17 meters or more.
“This study provides, for the first time, an explanation of the function and construction process of several colossal structures at this site in Saqqara,” say Landreau and his team. They assume that, in parallel with the hydraulic lifting system, common construction techniques such as ramps, hoists and pulleys were also used. “It is unlikely that ancient Egyptian architects used a single construction technique. Instead, different methods were used to adapt to different constraints or unpredictable events such as a dry period,” they explain. However, Landreau and his colleagues also admit that further research and excavations on site are needed to confirm their interpretation of the structures.
Source: PLOS, scientific article: PLoS ONE, doi: 10.1371/journal.pone.0306690