ABSTRACT
Water, regardless of the source, is conveyed to the waterworks for treatment and distributed to the users. Conveyance from the source to the point of treatment occurs by aqueducts, pipelines, or open channels, but the treated water is normally distributed in pressurized closed conduits. After use, whatever the purpose, the water becomes wastewater, which must be disposed of somehow, but almost always ends up being conveyed back to a treatment facility before being outfalled to some water body, to begin the cycle again. We call this an urban water cycle, because it provides a human-generated imitation of the natural water cycle. Unlike the natural water cycle, however, without pipes the cycle would be nonexistent or, at the very least, short-circuited. In open-channel flow, water is transported over long distances through aqueducts to locations where it is to be used or treated. Selection of an aqueduct type rests on such factors as topography, head availability, climate, construction practices, economics, and water quality protection. Along with pipes and tunnels, aqueducts may also include or be solely composed of open channels (Viessman and Hammer, 1998).
