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Eight prehistoric wells dug to a depth of similar to 2 m below the modern ground surface were found in the alluvial sediments of McClellan Wash on Gila River Indian Community in southern Arizona. Charcoal from the sediments filling the wells yielded radiocarbon ages of similar to 1000 B.C. The time in which wells were dug coincides with a period of general regional aridity and high ENSO activity in the American Southwest. Digging to access water may have occurred in response to period(s) of resource uncertainty, or as a logistical activity that engaged increasingly resource-tethered Late Archaic/Early Agricultural populations. These activities laid the foundation for agricultural practices that eventually became the dominant mode of subsistence in the low-lying areas of the Sonoran Desert. (C) 2012 Elsevier Ltd. All rights reserved.