Carbonates from the Ancient World's Longest Aqueduct: A Testament of Byzantine Water Management

The fourth- and fifth-century aqueduct system of Constantinople is, at 426 km, the longest water supply line of the ancient world. Carbonate deposits in the aqueduct system provide an archive of both archaeological developments and palaeo-environmental conditions during the depositional period. The 246-km-long aqueduct line from the fourth century used springs from a small aquifer, whereas a 180-km-long fifth-century extension to the west tapped a larger aquifer. Although historical records testify at least 700 years of aqueduct activity, carbonate deposits in the aqueduct system display less than 27 years of operation. This implies that the entire system must have been cleaned of carbonate, presumably during regular campaigns. A 50-km-long double-aqueduct section in the central part of the system may have been a costly but practical solution to allow repairs and cleaning of the aqueducts of carbonate to ascertain a continuous water supply to the city. The fifth-century channel was commonly contaminated with clay, caused by the nature of the aqueduct system and possible local damage to the channel. This clay-rich water could have been one of the reasons for the construction of large reservoirs in Constantinople.