Arizona's alluvial basins have suffered an overall storage loss of 74.5 million acre-feet of water since their development began, according to a study published by the USGS, representing both gains and losses to from the groundwater system.
"Groundwater withdrawals accounted for the largest share of the water budget, with nearly 2.4 million acre-ft per year withdrawn from the study area in recent years. Evapotranspiration from groundwater was estimated at nearly 1.3 million acre-ft per year" from the more than 73,000 square miles of alluvial basins in Arizona.
Ref: Tillman, F.D, Cordova, J.T., Leake, S.A., Thomas, B.E., and Callegary, J.B., 2011, Water availability and use pilot; methods development for a regional assessment of groundwater availability, southwest alluvial basins, Arizona: U.S. Geological Survey Scientific Investigations Report 2011-5071, 118 p. and online appendix.