As I have mentioned before, the Nabataeans were able to control the water supply, that led to the rise of the desert city, creating an artificial oasis. The area is visited by flash floods and archaeological evidence demonstrates the Nabataeans controlled these floods by the use of dams,cisterns and water conduits. These innovations stored water for prolonged periods of drought, and enabled the city to prosper from its sale. (Wikipedia)
Here is one of the dams in the narrow valley.