Nilometers, El-Niño, and vlimate variability

Abstract

Nilometers have been used for gauging the level of water in the Nile river for more than five millennia. The written records describing some of these measurements represent the longest written records for any hydrological phenomenon. They describe interannual fluctuations in the Nile river flow which are closely associated with El Niño phenomenon. Here, we use information about long-term variability in El Niño occurrences that has been extracted from the Nilometers records to test the significance of the recent trend in the frequency of El Niño years. We show that the observed frequency of El Niño years during the last two decades is rather high compared to the long-term statistics that are computed from about a thousand years of Nilometers data; however similar levels of activity have been observed during the first millennium.