The Nilometer at Roda Island provides an important long-term record of the water levels in the Nile River. In 1936, Jarvis speculated: "In spite of all the changing, uncertain, and erroneous factors that must be considered in connection with records of stages of the Nile River, it is believed that they disclose some important information; and there is a fair prospect that they may yield more data with further study . . ." This statement turned out to be very prophetic. Data collected from the Nile River have spurred the development of a whole field of mathematics (fractional Brownian motion and fractional Gaussian noise) along with a field of statistics concerned with the behavior of long memory time series. Gathered by Toussoun (1925), there exists a remarkable hydrological time series of minimum and maximum water levels for the Nile River. Starting in 622 AD and ending in 1922 AD, the first missing observation in the annual minima occurs in 1285. This leaves several continuous records to analyze, the longest one (662 years) is shown in Figure 2.
