Measuring the Nile Flood in the Greco-Roman Period

The Ptolemaic rulers were involved with the internal government of Egypt and collected taxes. The annual flooding of the Nile had a big impact on Egyptian agriculture, so taxes were exacted based on flood levels. In the beginning, a portable tool, called a Nilometer, was placed vertically into the Nile to measure the flood levels.

It was probably a long reed stick on which different levels were marked. To assess taxes fairly, the Ptolemaic rulers built temples along the Nile and installed Nilometers in them. The Nilometer uncovered on Philae Island is a staircase with reliefs of Nilometers with arms carved on its internal walls, along with the timing and duration of the flood. During the Roman period in Egypt, the Roman rulers showed interest in the monuments built along the Nile with Nilometers, but did not construct any new buildings themselves.

Until the time of the Emperor Constantine, a portable Nilometer was kept in the temple of the god Serapis. The ancient Egyptians believed that they were in debt to Serapis for bringing them the annual Nile flood. After every measurement that showed a rise in the Nile waters, they would return the portable Nilometer to the temple of Serapis. This became a ritual. The portable Nilometer was called "the arm, or branch, of the Nile."

When Constantine ordered the Nilometer to be placed in the Church of Alexandria, chaos ensued in Egypt. The people thought Serapis would be angry and not allow the Nile to rise that year. However, the Nile did rise. The Emperor Julian the Apostate later ordered the Nilometer to be returned to the temple of Serapis. It remained there until the time of The Emperor Theodosius the First, who ordered the entire temple to be destroyed