Oral Presentation NCGRT/IAH Australasian Groundwater Conference 2019

Hydrochemical variations of groundwater and spring discharge of the western Great Artesian Basin (314)

Stacey C. Priestley 1 2 , Paul Shand 2 , Andy J. Love 2 , Laura J. Crossey 3 , Karl E. Karlstrom 3 , Mark N. Keppel 4 , Daniel L. Wohling 5 , Pauline Rousseau-Gueutin 2
  1. ANSTO, Lucas Heights, NSW, Australia
  2. College of Science and Engineering, Flinders University, Adelaide, SA, Australia
  3. Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, USA
  4. Department of Environment and Water, Government of South Australia, Adelaide, SA, Australia
  5. Innovative Groundwater Solutions Pty Ltd, Wayville, SA, Australia

Objectives

The chemical variations of groundwater provide important clues to the geochemical processes responsible for water quality and evolution across the western GAB. The objective of this study was to examine the hydrochemical variations of groundwater and spring discharge along the entire western GAB expanding on several key results from a 4 year project studying the hydrochemistry of the western GAB presented in Love et al. (2013) and Love et al. (2013).

Design and Methodology

The dataset comprises data collected during the Allocating Water and Maintaining Springs in the Great Artesian Basin project funded by the National Water Commission (Love, et al., 2013, Love, et al., 2013), with additional data from a government database, as well as, a number of published government reports and journal articles. Electrical balances and comparison of monitoring and duplicate data was undertaken to ensure the collated data were representative and accurate.

Original data and results

The regional hydrochemical trends generally support the modern interpreted flow paths, indicating that these generally represent the long-term flow paths. However, the chemical variations along the flow paths in the western GAB are complex with their composition being a function of several controlling processes, including recharge location, evapotranspiration and water-rock interactions. These processes being spatially variable cause groundwaters to be generally of Na-HCO3 type east of Lake Eyre and Na-Cl-(-SO4) type when originating from the western margin. Springs within the western GAB springs appear to be discharging water predominantly from the main GAB aquifer. However, springs on the Peake and Denison Inlier are either completely or partially fractured rock source and there are several springs discharging water with a component from a source other than the main GAB aquifer.

Conclusion

The source, evolution and several key geochemical processes responsible for water quality were identified through this study. However, work is still needed to fully characterise all water-rock interactions and geochemical processes occurring within the main GAB aquifer.