Later, during the Hellenistic period [323 B. C. (death of Alexander the Great)-146 B. C. (conquest of Greece by the Roman Empire)], further developments were made by Greeks in hydraulics, such as in the construction and operation of aqueducts, cisterns, wells, harbors, water supply systems, baths, toilets, and sewerage and drainage systems. During that period the political and economic situation changed leading to much more architectural development and urban beautification, of which aqueducts played a major role. During the beginning of the Hellenistic era several cities like Athens, Samos and Olynthos already had aqueducts. Probably during the middle of the 2nd half or the 3rd century B. C. the first aqueduct was constructed in Pergamon (Pergumum) bringing water from a spring in the mountains north of the city. This aqueduct was around 15 km and was constructed with fired clay pipes having an inner diameter of 13 cm and lengths up to 60 cm (Fahlbusch, 2006). Aqueduct pipes were laid in an excavated bed a little below the natural soil surface. Various stamps were imprinted on the pipes. This pipeline was constructed during the reign of King Attalos I and therefore has been called the Attalos aqueduct. An interesting note is that there is a saddle north in the mountain which the aqueduct was constructed so that the aqueduct outlet was at an elevation of 25 m higher than the crest of the saddle so that a pressurized pipeline, inverted siphon, was necessary. This very well could have been the first large-scale application of pressurized pipes during antiquity (Fahlbusch, 2006).
The progress in science during the Hellenistic period provided a new technical expertise. Hellenistic aqueducts usually used pipes, as compared to the Roman masonry conduit. Furthermore, following the classical Greek tradition, the aqueducts continued to be subterranean for security reasons (not to be exposed to aliens, e. g. in case of war) but also for the safety of the construction during earthquakes which are frequent in the area. This again contrasts the Hellenistic technology with the later Roman technology, whose apparent characteristic was the use of the arches and aqueduct bridges.
Greek aqueducts generally operated by free surface flow. However, during the Hellenistic period, the scientific progress in understanding hydrostatics and water and air pressure (due to Archimedes, Hero of Alexandria and others; Koutsoyiannis et al., 2007) allowed the construction of inverted siphons at large scales (lengths of kilometers, hydraulic heads of hundreds of meters). Hellenistic engineers constructed inverted siphons to convey water across valleys in aqueducts of several cities including Ephesus, Methymna, Magnesia, Philadelphia, both Antiochias, Blaundros, Patara (see Fig. 1.10), Smyrna, Prymnessos, Tralleis, Trapezopolis, Apameia, Akmonia, Laodikeia and Pergamon. These siphons initially were constructed of terracotta or stone pipes (square stone blocks to which a hole was carved as shown in Fig. 1.10). The need for higher pressures led to the use of metal pipes, specifically made from lead. Thus, one of the aqueducts of Pergamon includes an inverted siphon, constructed of lead pipes, over 3 km in length with a maximum pressure head of about 180 m.
The technology of cisterns developed through history and possibly peaked during the Hellenistic period. Because of the lack of adequate water supplies on most Greek islands water cisterns were used. During the Hellenistic period the technology of cisterns showed progress. During this time the water supply in several cities all over Greece was dependent entirely on precipitation. Rainwater was collected from the roofs, yards, and other open spaces (Angelakis and Spyridakis, 1996; Antoniou et al., 2006).
Aristotle in his Politics (vii, 1330b) written in the 320’s B. C. asserts that “cities need cisterns for safety in war.” During this time a severe 25-year drought required the collection and saving of rainwater (Camp, 1979). Also about this time cisterns were built in the Athenian Agora for the first time in centuries (Parsons, 1943; Crouch, 1993).
Fig. 1.10 Inverted siphon at Patara. Color version available in Appendix (copyright permission with L. M. Mays)
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