Some hydraulics of Roman aqueducts. Myths, fables, realities. A hydraulician's perspective
Roman aqueducts supplied waters to cities for public baths (thermes) and toilets (latrines) (HODGE 1992, FABRE et al. 2000), in addition of public fountains. They were long subterranean conduits, following contours lines, with flat longitudinal slopes : i.e., 1 to 3 m per km, even less at Nîmes (0.24 m/km). Numerous aqueducts were used for centuries and some are still in use (e.g. Carthage, Mons). Their construction was a huge task, often performed by the army under the guidance of military hydraulic engineers. Their cost was extra-ordinary considering the real flow rate (i.e. less than 400 L/s) : about 1 to 3 millions sesterces per kilometre in average (FEVRIER 1979, LEVEAU 1991) (1). Despite superb ruins, little is known of the hydraulics of the Roman aqueducts. What was the flow rate ? How did they operate ? How were they designed ? Who were the hydraulic engineers ? How did they learn their expertise ?