1-157-591 - Ann Ronan Picture Library/Heritage-Images

Nilometer on the island of Roda, Cairo, Egypt, c1895. The annual flooding of the Nile was historically vitally important to Egypt because it governed the fertility of the soil and could mean the difference between abundance and starvation. Nilometers were developed in Ancient Egypt to measure the depth of the water in the Nile, enabling comparative historical records to be kept and allowing the priesthood to be able to announce the coming of the anticipated flood. The nilometer at Roda was built in 861, but was on the site of a much earlier version. The construction of the Aswan dams in the 20th century enabled the Nile's flooding to be controlled by man, rendering the nilometer obsolete.