The Pont du Gard is a bridge, part of the Roman aqueduct of Nîmes, which was built by the Roman Empire between AD 40 and 60 to transport fresh water across the Gard river. The Pont du Gard is 275 meters (900 feet) long, 50 m (160 ft) high, with a maximum span of about 2.5 m (8.5 ft); it was actively used as a source of fresh water by the citizens of Nîmes between the first and sixth centuries AD.
The aqueduct of Nîmes was fed exclusively by the freshwater karstic springs from Eure at Uzès. The water passed over a series of underground and above ground (covered) structures to the catchment basin in the city of Nîmes, a distance of about 50 kilometers (31 miles) with an elevation drop of about 12 meters (40 ft), or about 24 centimeters (10 inches) per kilometer.
A recent detailed analysis (Bossy et al.) of the intact remains of the aqueduct found that discharge was likely between 200 and 400 liters (50-100 gallons) per second.
Bossy G, Fabre G, Glard Y, and Joseph C. 2000. Sur le fonctionnement d’un ouvrage de grande hydraulique antique, l’aqueduc de Nîmes et le pont du Gard (Languedoc, France). Comptes Rendus de l'Académie des Sciences - Series IIA - Earth and Planetary Science 330(11):769-775.
For more information on Roman water control the article Aqueducts, Water Supply and Sewage in Ancient Rome from About.com's guide to Ancient History, N.S. Gill
This glossary entry is part of the Dictionary of Archaeology.