Tuesday, May 11, 2010
[Image Courtesy of Egypt's Supreme Council of Antiquites (SCA).]
"The structure, 7 meters (23 feet) in diameter, was encircled by a spiral staircase descending into the Nile. The steps allowed for a quick reading of increase in water level, thus forecasting floods." - Discovery News
In ancient times the Nile would overflow its banks between June and September. The ancient Egyptians divided their year into three seasons with the period of inundation being one of the three. Tax levels were set based on the quantity of the anticipated flood. So, predicting the quantity of the inundation became a carefully guarded responsibility of select priests and many nilometers were enclosed in temples to exclude all but priests and Egyptian rulers.
The simplest nilometer was a marked vertical column submerged in the waters of the river. A very ornate version of this design, built in 861 CE by the Abbasid caliph al-Mutawakkil, can still be seen on the island of Rhoda in central Cairo.
The second type used a a flight of stairs leading down into the water, with depth markings along the walls. The best known example of this kind can be seen on the island of Elephantine in Aswan. [Image courtesy of Wikimedia Commons user Rajor]
The type found along the Avenue of the Sphinxes represents the third and most elaborate design that incorporated a cistern connected to the river by a channel. Another example of this type can be seen at the Temple of Kom Ombo north of Aswan