The use of environmental tracers to determine relationships among aquifers in the Lower San Pedro River basin, Arizona

Abstract

The chemistry of ground water from the Lower San Pedro River basin between Reddington and Mammoth, Arizona, was studied. Objectives were to determine (1) recharge and discharge relationships among aquifers through a comparison of their water chemistries and (2) whether copper mill tailings at San Manuel have affected ground-water quality. The study area has four aquifers: (1) the Catalina aquifer along the basin's western flank, (2) the Galiuro aquifer along the eastern flank, (3) the artesian aquifer, and (4) the channel aquifer. The latter two are in the center of the basin. This study produced the following conclusions: Ground water from the Catalina and Galiuro aquifers recharge the artesian aquifer. The age of ground water in the artesian aquifer is between 7,700 and 13,800 years. The channel aquifer is recharged by the artesian aquifer and intermittent surface flows. The chemistry of water in the channel aquifer is largely controlled by the dissolution of evaporites. There is no evidence that the mill tailings at San Manuel have affected ground-water quality.