The water supply and distribution system of the Nabataean city of Petra in southwestern Jordan has been explored and mapped. Analysis of the system indicates exploitation of all possible water resources using management techniques that balance reservoir storage capacity with continuous flow pipeline systems to maintain a constant water supply throughout the year. Nabataean Petra was founded c. 300 bc; urban development progressed with later Roman administration of the city starting at ad 106; Byzantine occupation continued to the seventh century ad. Trade networks that extended throughout much of the ancient Near East and Mediterranean world intersected at Petra, and brought not only strategic and economic prominence, but also impetus to develop water resources fully to sustain demands of increasing population and city elaboration. City development was influenced by artistic, cultural and technological borrowings from Seleucid, Syro-Phoenician, Greek and Roman civilizations; the Petra water-distribution system included hydraulic technologies derived from these contacts as well as original technical innovations that helped to maintain the high living standard of city dwellers throughout the centuries. Analysis of the Nabataean water network indicates design criteria that promote stable flows and use sequential particle-settling basins to purify potable water supplies. They also promote open channel flows within piping at critical (maximum) flow rates that avoid leakage associated with pressurized systems and have the design function to match the spring supply rate to the maximum carrying capacity of a pipeline. This demonstration of engineering capability indicates a high degree of cognitive skill in solving complex hydraulic problems to ensure a stable water supply and may be posited as a key reason behind the many centuries of flourishing city life.