Stable Isotope Altitude Effects in Precipitation: Applications in Mountain Block Groundwater Studies

Presented on Monday, March 16, 2015
Christopher J. Eastoe, Ph.D., Department of Geosciences, University of Arizona, Tucson, AZ

Isotope altitude effects consist in decreases in δ18O and δD  of precipitation with increasing altitude.  Such effects may be attenuated or absent in interior mountain ranges.  A nine-year data set in Tucson basin, Arizona, presented as amount-weighted seasonal averages of δ18O and δD, shows that altitude effects are present in some, but not all, seasons.    Long-term average altitude effects (δ18O) in Tucson basin are -1.1‰ per 1000 m in winter (November-May) and -1.6 ‰ per 1000 m in summer (June-October).  Comparable effects exist on the Mogollon Rim near Flagstaff, Arizona.  In relation to the long-term means  for Tucson basin, stable O and H isotope data from springs in the Santa Catalina Mountains indicate mainly winter recharge at the range crest,  but either selective winter recharge from certain cold storms, or winter + summer recharge at lower elevations.  If most precipitation in the Santa Catalina Mountains runs off into the basin, then recharge to basin sediments occurs in both winter and summer from Tanque Verde Creek and tributaries.  From the Cañada del Oro drainage, recharge occurs chiefly in winter.

MP3 Presentation Slides

Christopher J. Eastoe, Ph.D.
Department of Geosciences, University of Arizona, Tucson, AZ
Chris Eastoe received a Ph.D. in Economic Geology from the University of Tasmania in 1979. He worked in the Department of Geosciences, University of Arizona from 1982 to 2015, where he was a Staff Scientist specializing in isotope geochemistry.
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