Byzantium's Amazing Aqueducts
Whenever the Diggings tour takes me to Istanbul I always look forward to the ride in from the airport, waiting to catch the first glimpse of the famous walls that kept the city safe for a thousand years. As we make our way toward our hotel in Taksim Square, I ask the coach driver to go the long way round Seraglio Point so that I can have a chance to tell people the story of Sultan Ibrahim the Mad, who in the 1600s cleared out his harem to make way for new stock by having all his wives and concubines sewn into weighted sacks and dropped into the Bosphorus. It is claimed that for years afterwards divers could see the sacks swaying gently in the underwater currents. It is also claimed that one girl's sack wasn't weighted and she floated to the surface where she was rescued by a French ship and taken to Paris, where she made a sensation!
On other excursions, however, I am content for the driver to take the "short-cut", though to be honest the traffic on the "short-cut" is so bad that while it may be shorter in distance I doubt that it is shorter in time. This road climbs up over the peninsula and drops down the other side towards the Golden Horn, but as it does so, it passes beneath the arches of a huge aqueduct that emerges from the crowded buildings on one side of the road and disappears among the buildings on the other. It is an impressive example of Roman architecture and, taken in conjunction with the huge cistern of Yerebatan Saray, gives me a chance to talk learnedly about the water supply in Roman cities.
I now have much more to say on the subject!
In 1996 Professor K. C. Çeçen published the fruits of his researches into the water supply of Constantinople. His initial studies were among the records of Greek, Roman, Byzatine and later Muslim historians and architects, some of whom had commented on the search of the capital for enough water to supply its half-million inhabitants. For example, around AD 950 the Muslim writer Haroun ibn-Yahya wrote:
There is at Constantinople an aqueduct where water comes from the country called Bulgaria. This water flows towards the aqueducts from a distance equal to a voyage of twenty days and, when it enters the city, it divides itself into three sections; one part goes towards the imperial palace, a second part into the prisons of the Muslms and the third part into the baths of the patricians, and the population of the town drinks from the water which is lightly salted.
At first sight that sounded incredible, because the nearest point in Bulgaria is ninety miles away in a direct line (but as that line involves crossing a bay of the Black Sea, it is clearly not a feasible route for an aqueduct!) Professor Çeçen's next step, therefore, was to get in his car and start exploring the countryside around Istanbul.
The results were startling but they enabled him to publish the first ever map of Constantinople's water supply. In the time of Hadrian the little town of Byzantium was supplied by an aqueduct that ran north, around the end of the Golden Horn and into the hilly area known as the Forest of Belgrade. Several branches went out from the main aqueduct to tap into springs or streams and bring them down to the city.
When Constantine selected Byzantium as the site of his capital city, New Rome, this aqueduct could not supply enough water for the growing population and Valens, builder of the aqueduct we see on the short-cut, built further branches extending off to the north-west as far as the area around Danamandira and Pinarca, more than half-way to the Bulgarian frontier.
Most people, when they hear the word "aqueduct" think of something like the Pont du Garde near Nimes in France, a small water channel supported by tall arches. In fact aqueducts ran in channels cut in the ground and covered by stone slabs and tunnels and bridges, which were expensive and time-consuming to construct, were only used when absolutely unavoidable.
Some people say that the Romans were unaware that if you lay a closed pipe down one side of a valley and up the other, water will flow through the pipe so long as the outlet is lower than the inlet. Roman engineers were quite well acquainted with that fact and it was actually used at Pergamon to take water to the top of the acropolis. The problem was not knowledge but technology, for at the bottom of the valley the water pressure would be very great: pottery pipes would simply burst, stone conduits would leak, and lead pipes - which were very expensive - would burst at the seams.
As a result Roman aqueducts were, for the most part, constructed like British transport canals and followed the contours of the ground to provide a constant gradient. Roman engineers accomplished amazing feats to ensure that the channels of their aqueducts ran smoothly and evenly. One of the aqueducts that supplied Jerusalem, for example, ran for more than 25 miles through tunnels and over valleys at an average gradient of 0.09% (that is, a drop of 1 foot in 1100 feet distance.) This is believed to be the water supply built by Pilate and for which he raided the temple funds.
Although the furthest spring that supplied Valens' aqueduct was only about 40 miles from Constantinople as the crow flies, because the aqueduct followed the contours the total length of the channel was 134 miles from its source to its destination in Constantinople. This was dwarfed, however, by the aqueduct built by Theodosius - the man responsible for the famous walls - who extended Valens' work to Vize, which is indeed in Bulgaria. At 210 miles in length, this is the longest single aqueduct of the ancient world. However the aqueduct has a number of branches which enable it to tap into various water sources along the way, and when these are included, the total length of the aqueduct is a staggering 370 miles!
The amount of water supplied by these aqueducts was truly amazing. Not only did the system have to provide drinking water for half a million people and water for household use, but it also supplied the many public baths in Constantinople and in addition filled the cisterns of the city during the winter to compensate for the reduced water supply in summer. We don't have any figures for the Constantinople aqueducts, but we know that the eleven aqueducts which supplied Rome could provide 248,286,350 gallons of water every day or 2,873 gallons every second! Even with modern pumps and high-pressure water systems, that is an impressive figure and when we consider that it all flowed along man-made channels using nothing but gravity, we are lost in admiration for the skill of the Roman engineers.
Professor Çeçen's work has been supplemented by that of Professor James Crow, Dr Jonathan Bardill and Dr Richard Bayliss who have been working on the Anastasian Wall Project. Much of the area through which these aqueducts run is still heavily forested and difficult of access, which has been most fortunate as the remoteness has contributed to the remarkable state of preservation of many sections of the aqueduct. Elsewhere in the Roman empire these mighty monuments of antiquity have been devastated by stone robbers or at the very least destroyed by invading armies, but hidden in the remote valleys and wooded hillsides, Constantinople's aqueducts have survived with no more damage than that wrought by time and nature.
The next time I see Valens' Aqueduct striding across the road I shall view it with greater interest and much greater respect.
Anastasian Wall Project The Anastasian Wall was built around AD 500 to keep the Bulgars out of the Tracian peninsula and runs for 42 miles from the Sea of Marmara to the Black Sea. The wall's remains are being threatened by the growth of Istanbul and its suburbs, so the Project aimed to record as much as possible while it can still be seen in its natural setting. As the Anastasian Wall cut across the line of the aqueduct, it was natural that the team should take an interest in it and it is worth visiting the project's website for further information about both.Return
© Kendall K. Down 2009
