Gadara holds one of the world’s longest underground aqueducts

Gadara has been identified as the ancient city half-hidden beneath modern Umm Qais in Jordan. 

Until late Hellenistic times, the citizens of Gadara had to rely on a variety of cisterns that collected rainwater. So far, no less than 75 such reservoirs have been identified with a storage capacity varying from 6 to 450 cubic meters. After the arrival of the Romans in the 1^st century BC, the growing population spread out over a wider area, needing more water than the cisterns could provide. 

Water had to be brought into Gadara from a spring 11 kilometers away. It probably flowed through a series of clay pipes buried underground, called Qanat Turab, making a detour around the valleys. Near Gadara, the water crossed another valley by means of a bridge and reached a tunnel under the city’s Acropolis. From here, it was distributed to the baths, Nymphaeums, and houses. 

By the end of the 1^st century AD, however, the population of Gadara and neighboring settlements had exploded to reach about 50,000 people. To meet their needs, a daily debit of 300-400 liters per person was required. Together with the cities of Adra’a and Abila, Gadara decided to build a second long-distance water supply running through a series of tunnels cut in the rock. The project, known as Qanat Fir’aun, was started in 90 AD to be completed in several phases by 210 AD. It is known to have been functioning until the devastating earthquake of 747 AD, which destroyed Gadara. 

[Picture from Culture in Crisis, credit Paul Fischer]

I already touched on the subject in my earlier post, Preservation of the Roman aqueduct at Gadara, without digging deeper into the prowess of the Roman engineers. This elaborate structure started at a reservoir at Wadi Harier, near the Syrian border village of Dille, with a storage capacity of 4 to 6 million cubic meters. The water covered a distance of 170 kilometers to Gadara using gravity, in this case, a gradient of about 217 meters! How these engineers from antiquity managed to figure this out without the help of our modern technology is a pure wonder. For a good 100 kilometers of its course, the water ran through a system of tunnels. On its way, 14 tributaries from Lake Muzarib in southern Syria and several springs added their waters to the main stream. For the maintenance of the entire system, karezes or qanats, providing underground access, were added at regular intervals. 

Access to both aqueducts can be found on the Acropolis of Gadara, i.e., where the remains of the abandoned Ottoman village of Umm Qais now stand. Today’s tourist can visit the last section of this 170-kilometer-long tunnel in a guided tour. A real treat!