A leat is the name, common in the south and west of England and in Wales, for an artificial watercourse or aqueduct dug into the ground, especially one supplying water to a watermill or its mill pond. Other common uses for leats include delivery of water for hydraulic mining and mineral concentration, for irrigation, to serve a dye works or other industrial plant, and provision of drinking water to a farm or household or as a catchment cut-off to improve the yield of a reservoir.
The Devonport leat near Nun's cross farm
The aqueducts at Dolaucothi
Devonport leat showing sluice gates
An aqueduct is a watercourse constructed to carry water from a source to a distribution point far away. In modern engineering, the term aqueduct is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose. The term aqueduct also often refers specifically to a bridge carrying an artificial watercourse. Aqueducts were used in ancient Greece, ancient Near East, and ancient Rome. The simplest aqueducts are small ditches cut into the earth. Much larger channels may be used in modern aqueducts. Aqueducts sometimes run for some or all of their path through tunnels constructed underground. Modern aqueducts may also use pipelines. Historically, agricultural societies have constructed aqueducts to irrigate crops and supply large cities with drinking water.
The Central Arizona Project carries water from the Colorado River to central and southern Arizona.
Medieval Deccan aqueduct in Hampi
Nabataean aqueduct in Petra, Jordan
The multiple arches of the Pont du Gard, in Roman Gaul. Its lower tiers carry a road across the river, and the upper tiers support an aqueduct conduit that carried water to Nimes