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Nilometer

Cairo - Capital Cities

What: Nilometer

Where: Rhoda Island, Central Cairo

When: 861 AD

Who: Construction was ordered by Abbasid Caliph al-Mutawakkil. Built on an earlier Nilometer approx. 715AD

Why: Device for measuring the River Nile’s water level during the annual flood season

History

The Nile remains a critical factor in Egyptian life. Knowing the levels of the water in the Nile has been of great importance to officials for more than 5,000 years. The Nilometer on Rhoda Island was ordered to be constructed in its present form in 861AD by the Abbasid Caliph al-Mutawakkil and was built on the earlier Nilometer of approx. 715AD. It is a more refined version of the Roman and Pharaonic Meters.

It is built around the Stilling Well that extends well below the level of the water from the Nile. The way the Meter is read is by the Nile water flowing into one or more of the 3 tunnels situated at different levels of the Stilling Well. The center of the Well is supported by a marble column known as a Corinthian capital. Measuring the water level is done by reading marks which are etched into the column.

The Marks are known as Cubits which today equates to half a meter per Cubit. The Rhoda Island Nilometer is marked with 19 Cubits, meaning that this Nilometer can measure water levels up to approximately 9.5m. The most prosperous level of Nile Flood for Cairo was 16 Cubits. A lower level of Cubits could lead to drought and then famine and a higher level of Cubits could mean a catastrophic flood.

Records

The Nilometer’s records began in 622AD and ended in 1922AD with only a few missing records, the first one missed in 1285AD.

Fath al-Khalij : Opening of the Canal Festival 

The Khalij Canal begins opposite Rhoda Island in Cairo. 

It was blocked with an earth dam and was only opened when the Nile water level reached 16 cubits.

When the Cubits were reached with the Nile’s Summer Flood then river water was used to fill the canal. 

Those who witnessed the Festival called it, “Cairo’s most spectacular festival”. 

Near the Nilometer was a mosque for prayers and in the Bad years where the Flood was not certain, the celebrations were cancelled, and prayers and fasting were held instead.