3 Geomorphological, Hydrologic, and Geothermal investigations of basin aquifers in Baja California Sur (BCS), Mexico

The session will explore BCS basins, focusing on groundwater storage, evaporation, runoff and transport mechanisms, featuring experts on thermal and shallow groundwater interactions, soil mapping for hydrological planning, geomorphology, and human impacts on water balance.

Wednesday, 22 April 2026
8:00 AM - 12:00 PM
LMH, Isla Carmen

18O and 2H in rain, surface, and groundwaters in Baja California, insights into groundwater recharge in a semiarid environment.

Paper number: 3-1
Program: Technical Sessions
Time: 8:05 AM – 8:20 AM

Authors

  • Thomas Kretzschmar Presenting Author
    Centro de Investigación Cientifica y de Educación Superior de Ensenada, Ensenada, Baja California
  • Anna Espinoza
    Centro de Investigación Cientifica y de Educación Superior de Ensenada, Ensenada, Baja California
  • Tereza Cavazos
    Centro de Investigación Cientifica y de Educación Superior de Ensenada, Ensenada, Baja California
  • Luisa Andrade
    Centro de Investigación Cientifica y de Educación Superior de Ensenada, Ensenada, Baja California

Abstract

This paper presents a comparison of the results of stable isotopes of δ180 and δ2H from groundwater and surface water samples collected in different sampling periods (from 2004 to 2025) with those of rainwater collected between 2017 and 2025. The total number of groundwater and surface water samples taken and analyzed were over 250 sites while the rain samples consisted of about 130 samples. The values obtained in the rain samples show a large variation in their isotopic composition ranging from -1.71 to -7.96 for δ180 and from -7.05 to -48.67 for δ2H. Based on the results of the isotopic composition of the stable isotopes of δ180 and δ2H in the rain samples, it was possible to construct a regional meteoric line. The values of the groundwater samples vary between -3.50 and -7.37 for δ180 and between -24.3 and -47.79 for δ2H. Surface water samples (streams) vary between -3.07 and -4.05 for δ180 and between -20.28 and -25.91 for δ2H.

 

Furthermore, these results were correlated to the precipitation events, the type and direction as well as temperature and humidity to be able to explain possible evaporation effects on the stable isotope data. 

 

Then these results were correlated to the recharge behavior of this semiarid watershed dominated by mountain front an mountain block recharge. 

ACKNOWLEDGEMENTS

The authors thank CONAHCYT for the postdoctoral support and the Rio Arronte foundation for their financial support through the “Acuerdos del Acuífero”project.

Geological Society of America Abstracts with Programs. Vol. 58, No. 3

doi: 10.1130/abs/2026CD-410790

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