Professor Gedeon Dagan
My Reflections on Ancient and Modern Hydrology
To People of The World:
The material herein is based on the lecture of acceptance of the 2005 Horton Medal of the American Geophysical Union. It was published in EOS, the weekly bulletin of AGU, vol. 87, No. 7, p.75, 2005.
Hydrology: one of the oldest professions in the world…
This reflection was caused by accident (like many other discoveries) due to a visit to a fascinating archeologic-al site in Israel, at Tzipori (near Nazareth). This was a flourishing town during the Roman and Byzantine periods. One of the interesting and enigmatic remnants dug recently is a beautiful mosaic called “The Nile Festival”, which dates from the Byzantine period (5th century). It portrays a legendary Nile populated by different beasts, an Amazon and the detail shown in the enclosed photo, which depicts in a symbolic manner the construction of a Nilometer. This is a marked pillar that served to measure quite accurately the level of the Nile.
The first Nilometers and mention of their level records go back to the 3rd millennium BC and even earlier. The fertile Nile valley made possible the existence of the ancient Egypt-ian civilization. The readings were used by the hydrologists of the Pharaohs administration (persons of high standing, most probably priests) in order to predict periods of draught or floods, both detrimental to the agriculture. In turn, these analyses and predictions were employed in order to fix the level of taxation of the population and storage policy.
THE COMMON GROUND
There are four constituents of the ancient hydrology that are shared by the modern one:
• Hydrology is a quantitative discipline: it deals with data and with mathematical analysis.
• Hydrology is an applied science: the motivation and aims were related to the needs of society.
• Hydrology dealt with prediction under uncertainty: the ancient hydrologist had to use sophisticated time series analysis in order to predict occurrence of extreme events.
• Hydrology is intertwined with economy, political and social issues: predictions had a serious impact on the sustainability and wellbeing of society.
My work on contaminant transport by ground-water, that takes place in an environment of a complex spatial structure that calls for analysis by advanced tools, shares the above four ingredients with ancient hydrology.