The Nilometer at Elephantine Island is of greater importance then it receives in most books about Egypt. While there were usually from two to four Nilometers located on the Nile for measurement, the one at Elephantine Island, which is located at the first Cataract of the Nile, was prime. This was the earliest warning of fluctuations in the River's depth, and changes would be recorded and published. This information would be used to predict silt levels and thus manage the agriculture which was completely dependent on the flooding levels of the Nile River. Taxes were based on the amount of flooding received up until the middle of the 20th century.
This Nilometer is one of the most intact relics of Elephantine Island. Remember that a Nilometer was in fact an instrument. Unlike many types of artifacts, an instrument and particularly an instrument as important as the Nilometer had to be kept in a state of repair to be useful. The Elephantine Nilometer has been dated to Roman times, with markings in cubits (about 2 1/3 inches). However, this was probably only a restoration, and while all of the original pieces have been replaced at some point, there has probably been a Nilometer here, are near here for as long as Nilometer have existed. There are inscriptions from the reigns of Tuthmosis III and Amenophis III (18th Dynasty) and of Psammetichus II (26th Dynasty) near here. After having been idle for some time, the Nilometer was again rebuilt by the French and Arabs during the 19th Century and placed back in use. Hence, it now has markings in French and Arabic. Today, satellites are used to measure water levels, and the Aswan Dam has lessened the need for such instruments.