Water in the Desert
Writing in the first century BC, the ancient geographer Strabo described Petra as "having springs in abundance, both for domestic purposes and for watering gardens." Indeed, the Nabataeans chose this location not only for its fortress of rock cliffs, but also for its available water supply: this part of the desert saw a mere 6 inches (15 centimeters) of rain per year. Petra's local springs flowed enough for some families to fetch water daily, but these streams alone could not support a population of around 20,000 in and around the city.
The Nabataeans developed a sophisticated public waterworks fed by three larger springs located several miles from Petra. Systems of strategically placed rock-cut gutters lined with watertight plaster, combined with terracotta pipelines, followed the natural landscape to feed nearly 200 cistern tanks, many reservoirs and a nymphaeum, or public fountain house. Water was also diverted for agricultural use to support crops and herds, and the Nabataeans developed rules for water allocation to govern its consumption. According to a recent calculation, Petra's aqueduct system carried about 12 million gallons (40 million liters) of fresh spring water per day--enough to sustain a modern-day American population of more than 100,000.