Environmental tracers for quantifying surface water-groundwater interaction

Author: Sarah Anne Bourke

Bourke, Sarah Anne, 2014 Environmental tracers for quantifying surface water-groundwater interaction, Flinders University, School of the Environment

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This thesis presents new methods quantifying surface water-groundwater interaction, which have different sensitivities to pre-existing methods. Firstly, a new technique using of stream radon-222 concentrations for quantifying hyporheic exchange is presented, which is particularly sensitive to hyporheic exchange on spatial scales of tens of metres, with sub-surface residence times of days or more. Secondly, the use of carbon-14 activity in dissolved inorganic carbon in streams as a tracer of discharging groundwater is presented. This new method allows for larger spatial sampling intervals than other gaseous tracers. Furthermore, if the groundwater influx can be quantified independently, then stream carbon-14 activity can be used to infer the carbon-14 activity of discharging groundwater. Finally CFC-12 and carbon-14 are used as the basis for mixing ratio calculations to detect recharge by mine water discharged along ephemeral creeks. These results are supported by excess air and terrigenic helium-4 amounts in production wells, which suggest substantial recirculation of water at the study site. The application of these techniques in future studies will allow for more robust estimates of the spectrum exchange fluxes associated with surface water-groundwater interaction.

Keywords: parafluvial,noble gases,DIC
Subject: Environmental Science thesis

Thesis type: Doctor of Philosophy
Completed: 2014
School: School of the Environment
Supervisor: Peter Cook