Aqueduct, AK wuh duhkt, is an artificial channel through which water is conducted to the place where it is used. The materials used for aqueduct construction may be masonry, concrete, cast iron, steel, or wood. Some aqueducts are tunnels dug through rocks, and others are canals in the earth. In many aqueducts, the outlet is so much lower than the water source that gravity alone carries the water. Where gravity is insufficient, the water is forced through the aqueduct by pumps.