The determination of seasonal variations in groundwater recharge by deuterium and oxygen-18 analysis for the Tucson Basin, Arizona

Abstract

The Tucson basin in southern Arizona covers an area greater than 600 square miles, and has an average fill of over 1,000 feet. Average rainfall is about 11 inches, with a little more than half occurring as convective storms in the summer and the rest are frontal storms in the winter. Summer storms usually originate in the Gulf of Mexico, and winter storms in the Pacific. All streams in the area are intermittent. This research attempts to see if it is feasible to determine recharge source areas and flow patterns' importance by studying the distribution of deuterium and oxygen-18 in precipitation and groundwater in the basin. Oxygen-18 values clustered around -5 per mil w.r.t. SMOW in the summer and -10 per mil in the winter. Deuterium content was -40 per mil w.r.t. SMOW in the summer and -75 per mil in the winter. This differentiation between summer and winter precipitation can provide information on the importance of seasonal rainfall to ground water recharge.