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An Integrated Environmental Geosciences Project in the Santa Cruz River Drainage Basin, Southern Arizona

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RIDLEY W. I¹., and, in alphabetical order, BERGER, B.R.¹, FINN, C.A.¹, GETTINGS, M.E.², HOUSER, B.B.², KING, T.V. V.¹, LICHTE, F.E.¹, SHANKS, W.C. III¹, WANTY, R.B.^{1   1}U.S. Geological Survey, Box 25046, MS 973, Denver, CO 80225, USA; ²U.S. Geological Survey, SW Field Office, 520 N. Park Ave., Tucson, AZ 85719, USA

The Santa Cruz River Watershed is composed of several structurally-controlled aquifer systems, surrounded by heavily mineralized recharge regions, that provide water of variable quality for Tucson, Nogales, Green Valley and the burgeoning developments in the area. The recharge areas include several world-class porphyry copper systems, epithermal precious metal systems and base-metal skarn systems. The aquifer systems are fed by surface water and both shallow and deep ground water. The river system also sustains one of the richest, most diverse riparian habitats in the southwestern USA that is threatened by bioaccumulations of toxic metal contaminants and includes several endangered species and other proposed-endangered species. The objective of this interdisciplinary study is to provide new information and interpretations that enhance our understanding of the nature of, and factors that control, shallow and deep ground-water flow and quality within the watershed region; a critical aspect of future anthropogenic and environmental management of this important river system. The emphasis is upon the sources, transportation, and fate of potentially toxic cations and anions, and hence the risk of natural ground-water contamination, by mineralized ground. Consequently, the project involves studies within the various structurally-controlled geologic blocks that form the recharge regions and studies within the sedimentary fill of the Tucson, Santa Cruz and Sonoita Basins. The presentation will reflect the interdisciplinary nature of the project and will include current information on our studies in: structural and lithologic geology; major-, minor-, trace-element, and stable-isotope geochemistry and reaction path modeling; high-resolution airborne and ground gravity/magnetics; and high-resolution AVIRIS remote sensing.

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