8. Tucson, Ariz.
Major Water Supply: local ground water
Population (U.S. rank): 543,000 (32nd)
Population Growth Rate: 20 percent since 2000
Average Annual Rainfall: 12.17 in.
The NRDC study rates Pima county, Arizona, where Tuscon is located, as an area with extreme risk of water shortage. The city is in the Sonoran desert, an extremely arid region which receives less than 12 inches of rainfall each year. Currently, the Tucson region uses about 350,000 acre-feet of water per year. At this rate, Tucson’s groundwater supply, which now provides the majority of the city’s water, has a very limited life span. In addition to this, the city is currently bringing in 314,000 acre-feet per year from the Colorado River under the Central Arizona Project. However, Tuscon is growing rapidly, adding more than 20,000 people since 2000. This, combined with the political uncertainty of the Central Arizona Project allocation, places Tucson at extreme risk for future water shortages.