Ancient Roman Aqueducts. Ancient Roman Aqueducts. An aqueduct is a water supply or navigable channel constructed to convey water. In modern engineering, the term is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose.n a more restricted use, aqueduct (occasionally water bridge) applies to any bridge or viaduct that transports water-instead of a path, road or railway-across a gap. Large navigable aqueducts are used as transport links for boats or ships.