The Basin and Range basin-fill aquifers that supply groundwater to most of the population of Arizona (and all of Nevada, parts of So. Calif, etc) constitute the 4th largest aquifer system in the U.S. [right, principal aquifer withdrawals for irrigation, public-supply, and self-supplied industrial uses; USGS C1323]
This comes from the new USGS Circular 1323 on "Ground-Water Availability in the United States"
[below, principal aquifers of the U.S. The Basin & Range basin-fill aquifers are labelled #1]
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