Thermal anomalies and the ground-water flow system south of the narrows, upper San Pedro Valley, Arizona

Abstract

Hydrologic conditions in the Upper San Pedro Valley are diverse and vary greatly in quantity and quality. The hydrogeologic system includes a permeable unconfined upper aquifer seperated from a lower aquifer by confining beds in the middle of the valley. Flowing wells are found in the St. David-Benson-Pomerene artesian area. Anomalously high ground-water temperatures down-gradient of this artesian area indicate a possible upward flowing portion of the confined aquifer. Temperature and head data were collected at 31 wells, mostly in the unconfined aquifer. Thermal gradients were measured at 20 wells, and areas of elevated heat flow were found to correspond with a rise in the underlying bedrock elevation. These data tend to support the hypothesis of upward advection of heat in the lower aquifer.