Where is the water going: an irrigation experiment using a natural isotopic tracer in karst SE, Australia
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Date
2014-05
Journal Title
Journal ISSN
Volume Title
Publisher
European Geosciences Union
Abstract
The karst unsaturated zone is a fractured rock environment associated with very heterogeneous water movement; spatial variability in the subsurface water storage; and fast preferential flow through fractures and fissures. These factors dominate the way in which water moves within the unsaturated zone in these environments, giving rise to flow path complexities less common in homogenous media. Currently there is limited research regarding karst infiltration/storage processes and potential evaporation in the unsaturated zone. Such processes may have the potential to alter the stable isotopic composition of groundwater. Caves provide a unique environment within which to examine exfiltration variability and flow dynamics in situ. In semi-arid environments evaporative processes in the unsaturated zone have been shown to directly alter the isotopic δ18O composition of cave drip waters, fractionating them towards heavier ratios, by a magnitude of 1-3 per mil relative to mean annual rainfall (Bar Matthews et al., 1996; Cuthbert et al., 2014). Here we present a novel isotopic drip water study from an artificial infiltration experiment at Wellington Caves, SE Australia. A series of four artificial infiltration events were initiated directly over Cathedral Cave, Wellington over as many days. The first event was spiked with a deuterium tracer and the subsurface response was monitored during several sampling campaigns over the following year. The infiltration study revealed: (1) isotopic break-through curves suggest a front of older water from the unsaturated zone storage arrived ahead of the infiltration water, (2) water residence times in the unsaturated zone were found to be longer than 6 months and, (3) large spatial heterogeneities existed in the proportion of exfiltrated deuterium tracer at different drip sites in the cave suggesting unique pathways and sources of water in the unsaturated zone. Implications from this study include the interpretation of paleo-climate speleothem records from semi-arid to arid environments. © Author(s) 2014.
Description
Keywords
Water, Environment, Isotopes, Caves, Ground water, Deuterium, Rocks, Fracturing, Subsurface structures, Ground water, Underground storage
Citation
Markowska, M., Baker, A., Andersen, M., Cuthbert, M., Rau, G., Jex, C., Rutlidge, H., Marjo, C., Roshan, H., & Treble, P. (2014). Where is the water going: an irrigation experiment using a natural isotopic tracer in karst SE, Australia. Paper presented at the European Geophysical Union Conference, 27 April - 2 May 2014, Vienna, Austria.