Nile -- measured by humans

The level of Nile River have been measured for more than five thousand years, with records stretching over 13 centuries. The Nilometer, in various forms, is a good example of historid water measurerment.

While Nilometer at Roda Island (shown above) is an important long-term record of the water, it has turned out to have unanticipated uses.
THM: If you can measure it accurately and regularly, do:
you never know what it uses will be.

Data from the Nile River have spurred the development of aspects of mathematics (Brownian motion and Gaussian noise) along with a field of statistics concerned with the behavior of long memory time series.

This nilometer gave a remarkable hydrological time series of minimum and maximum water levels for the Nile River from 622 AD to 1922 AD. Due to first missing observation in the annual minima about 1285, the continuous records to analyze, the longest one (662 years) is shown shown above. Recent studies (1999) show strong correlation between the Nile's water level and the existence of El Nino-so strong, in fact, that the Nile record can be used as a proxy for El Nino occurrence. This proxy reconstructed the history of El Nino for the past 1,300 years.

For example, the frequency of El Ninos in the 1990s has been greatly exceeded in the past. In fact, the period from 700 to 1000 AD was a very active time for El Ninos, making our most recent decade or two of high El Nino frequency look comparatively mild.

http://www.waterhistory.org/histories/cairo/