The longest aqueduct in history in sight: Archaeologists report on indications of the complex maintenance of the once 426 kilometer long water supply system of Constantinople. The facility, which was built in late antiquity, was cleaned of limescale deposits a few decades before it was no longer in use in the 12th century. Presumably, double water channels in special areas of the construction also made maintenance work possible during ongoing operations, the scientists report.
They are among the most impressive buildings of antiquity: Even today you can marvel at the monumental remains of aqueducts in some places of the former Roman Empire. The long-distance aqueducts were not invented by the Romans, but in their domain they became a trademark of their civilization. “The highly developed water supply was a revolutionary technical achievement of the Romans – the aqueducts transported water over great distances to the cities, to the baths or to the mines,” says Gül Sürmelihindi from Johannes Gutenberg University Mainz. More than 2000 Roman long-range aqueducts are known. Sürmelihindi and her colleagues now focused on the most spectacular: It served to supply Constantinople – today’s Istanbul in Turkey.
426 kilometers in length
The huge aqueduct system became necessary after the Roman emperor Constantine declared Constantinople the new capital of the empire in 330 AD. The city was strategically located very favorably, but sufficient fresh water supplies were not available locally. In order to guarantee the supply, an aqueduct system was built that brought water from springs far to the west. In order to keep up with the population growth, the facility was massively expanded again in the 5th century: With a total length of 426 kilometers, it finally became the longest aqueduct system of antiquity. The system consisted of masonry canals, 90 large bridges and several tunnels.
In order to gain insight into the use of the monumental facility, Sürmelihindi and her team examined the deposits in the remains of the pipeline system in various areas. This is limestone that was formed on the structures by the flow of water. Based on the thickness of the layers, conclusions can be drawn about the use, explain the researchers. In this context, it is evident from tradition that the complex was used well into the Byzantine period: in total, it was in operation for over 700 years – at least until the 12th century. Thus, thick limescale deposits would have been expected in the water-bearing parts.
Regular maintenance until the end
However, as the researchers report, during their investigations they came across a surprisingly thin layer of limestone in all areas of the facility. According to their analyzes, it corresponds to a storage period of only 27 years. Although the aqueduct is of late Roman origin, the lime in the canals therefore only dates from the Middle Byzantine era. From this, the scientists conclude: “The entire, 426-kilometer-long water pipeline must have been serviced and cleared of the deposits in the era of the Byzantine Empire, shortly before operations were stopped,” says Sürmelihindi. Presumably, the deposits were regularly removed beforehand as they could disrupt the flow of water, explain the archaeologists.
Sürmelihindi and her colleagues emphasize that this must have taken a lot of effort. According to them, a conspicuous substructure of the system was probably used for this maintenance work: In the central area of the aqueduct system there was an approximately 50 km long section with a double water pipe – one canal lay over the other – also over two-story bridges. “This system was probably set up for the cleaning and maintenance work,” says Sürmelihindi. The scientists explain that an uninterrupted water supply for the urban population was thus possible.
Source: Johannes Gutenberg University Mainz, specialist article: Geoarchaeology. Doi: 10.1002 / gea.21853