Evaluation de l'importance des unités argileuses dans les bassins alluviaux sur l'écoulement d'eau souterraine en utilisant des traceurs dissous et des isotopes: Cas du bassin moyen de San Pedro, Sud-Est de l'Arizona, USA

Translated title of the contribution: Evaluation of the importance of clay confining units on groundwater flow in alluvial basins using solute and isotope tracers: The case of Middle San Pedro Basin in southeastern Arizona (USA)

Candice B. Hopkins, Jennifer McIntosh, Chris Eastoe, Jesse E. Dickinson, Thomas Meixner

Research output: Contribution to journalArticle

3 Scopus citations


As groundwater becomes an increasingly important water resource worldwide, it is essential to understand how local geology affects groundwater quality, flowpaths and residence times. This study utilized multiple tracers to improve conceptual and numerical models of groundwater flow in the Middle San Pedro Basin in southeastern Arizona (USA) by determining recharge areas, compartmentalization of water sources, flowpaths and residence times. Ninety-five groundwater and surface-water samples were analyzed for major ion chemistry (water type and Ca/Sr ratios) and stable (18O, 2H, 13C) and radiogenic (3H, 14C) isotopes, and resulting data were used in conjunction with hydrogeologic information (e.g. hydraulic head and hydrostratigraphy). Results show that recent recharge (<60 years) has occurred within mountain systems along the basin margins and in shallow floodplain aquifers adjacent to the San Pedro River. Groundwater in the lower basin fill aquifer (semi confined) was recharged at high elevation in the fractured bedrock and has been extensively modified by water-rock reactions (increasing F and Sr, decreasing 14C) over long timescales (up to 35,000 years BP). Distinct solute and isotope geochemistries between the lower and upper basin fill aquifers show the importance of a clay confining unit on groundwater flow in the basin, which minimizes vertical groundwater movement.

Original languageFrench
Pages (from-to)829-849
Number of pages21
JournalHydrogeology Journal
Issue number4
Publication statusPublished - 2014



  • Confining units
  • Groundwater age
  • Hydrochemistry
  • Numerical modeling
  • USA

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)
  • Water Science and Technology

Cite this