Drip water isotopes in semi-arid karst: Implications for speleothem paleoclimatology

Research output: Contribution to journalArticlepeer-review


  • Andy Baker
  • Catherine N. Jex
  • Peter W. Graham
  • Pauline C. Treble
  • Martin S. Andersen
  • R. Ian Acworth

Colleges, School and Institutes

External organisations

  • University of New South Wales
  • Connected Waters Initiative Research Centre
  • Institute for Environmental Research, Australian Nuclear Science and Technology Organisation


We report the results of the first multi-year monitoring and modelling study of the isotopic composition of drip waters in a semi-arid karst terrane. High temporal resolution drip rate monitoring combined with monthly isotope drip water and rainfall sampling at Cathedral Cave, Australia, demonstrates that drip water discharge to the cave occurs irregularly, and only after occasional long duration and high volume rainfall events, where the soil moisture deficit and evapotranspiration is overcome. All drip waters have a water isotopic composition that is heavier than the weighted mean annual precipitation, some fall along the local meteoric water line, others trend towards an evaporation water line. It is hypothesised that, in addition to the initial rainfall composition, evaporation of unsaturated zone water, as well as the time between infiltration events, are the dominant processes that determine infiltration water isotopic composition. We test this hypothesis using a soil moisture balance and isotope model. Our research reports, for the first time, the potential role of sub-surface evaporation in altering drip water isotopic composition, and its implications for the interpretation of speleothem δO18 records from arid and semi-arid regions.


Original languageEnglish
Pages (from-to)194-204
Number of pages11
JournalEarth and Planetary Science Letters
Early online date12 Apr 2014
Publication statusPublished - 1 Jun 2014


  • Evaporation, Karst, Recharge, Semi-arid, Speleothem, Water isotopes