Oral Presentation NCGRT/IAH Australasian Groundwater Conference 2019

In updating its Information Guidelines (2018) the Independent Expert Scientific Committee on Coal Seam Gas and Large Coal Mining Development (IESC) identified the lack of use of environmental tracers in developing conceptual and numerical models and how they can be used in a risk context to reduce uncertainty.

Confidently identifying and evaluating causal pathways to impacts on water-assets is key to an efficient environmental assessment process. Environmental water tracers can often complement other techniques and offer an important means of gaining multiple lines of evidence to support conceptual models. Importantly, in some situations tracers may be the only feasible way of gaining information about systems at appropriate spatial and temporal scales. This presentation will provide an overview of the IESC’s environmental tracers factsheet, by explaining how tracers can be used in environmental impact assessments by:

1. outlining how tracers can fit into a risk-based framework; and
2. discussing five case studies where tracers have investigated:
   1. surface and groundwater connectivity: estimation of groundwater discharge into a section of the Gellibrand River, VIC;
   2. recharge sources: the relationship between surface water in a marsh (asset), alluvial groundwater and deep groundwater in the Hamersley Basin, WA;
   3. connectivity between different aquifers: groundwater movement between the coal seam and the alluvial aquifer in the Condamine River Catchment, Qld;
   4. using tracers to constrain a water balance: evaporation from temperate highland peat swamps on sandstone in the Sydney Basin, NSW; and
   5. improving groundwater modelling with tracer evidence: aquifers intersected by dewatering bores at a mine-site in the Pilbara, WA.

References to further reading materials are provided for more detailed technical explanations.