American and Egyptian archaeologists have discovered a rare structure called a nilometer in the ruins of the ancient city of Thmuis in Egypt’s Delta region. Likely constructed during the third century B.C., the nilometer was used for roughly a thousand years to calculate the water level of the river during the annual flooding of the Nile. Fewer than two dozen of the devices are known to exist.
“Without the river, there was no life in Egypt,” says University of Hawaii archaeologist Jay Silverstein, a member of the team who works at the site where the nilometer was found, near the modern city of El Mansoura. “We suspect it was originally located within a temple complex. They would’ve thought of the Nile River as a god, and the nilometer was this point of interface between the spiritual and the pragmatic.”
Before the completion of the Aswan High Dam in 1970, the Nile flooded the surrounding plains each year in late July or August. As the waters receded in September and October, they left behind a blanket of fertile silt that was essential for growing crops such as barley and wheat.
But the volume of the yearly flood varied widely. If the inundation was inadequate, only a small area of cropland would be covered with the life-giving silt, often resulting in famine. If the water level was too high, it would sweep away houses and structures built on the plain and ruin the crops. It’s estimated that the flooding was either inadequate or excessive roughly once every five years during the pharaonic period.
Water Gauge and Tax Table
Made from large limestone blocks, the nilometer was a circular well roughly eight feet (2.4 meters) in diameter with a staircase leading down into its interior. Either a channel would have connected the well to the river, or it would have simply measured the water table as a proxy for the strength of the river. Seven cubits—roughly 10 feet (3.04 meters)—was the optimum height for prosperity.
“During the time of the pharaohs, the nilometer was used to compute the levy of taxes, and this was also likely the case during the Hellenistic period,” says Robert Littman, an archaeologist at the University of Hawaii. “If the water level indicated there would be a strong harvest, taxes would be higher.”
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