Oral Presentation NCGRT/IAH Australasian Groundwater Conference 2019

Conceptualisation of groundwater systems in the Peel Region (WA) using multiple lines of evidence (537)

Olga Barron 1 , Matthias Raiber 1 , Christoph Gerber 1 , Axel Suckow 1 , Brett Harris 2 , Andrew Pethick 2 , JM Perraud 1 , Chris Turnadge 1 , David Rassam 1 , Mike Donn 1 , Geoff Hodgson 1
  1. CSIRO Land and Water, Perth, WA, Australia
  2. Curtin University, Perth, WA, Australia

Water availability is a critical factor for effective and sustainable regional development; it underpins business development options and plays an important role in the viability of capital investments; the Peel Integrated Water Initiative (PIWI) is such an example, which is part of the Transform Peel Program. Two of the main PIWI objectives include a detailed characterisation of the hydrogeological setting and a spatially explicit groundwater resource assessment for the region. Geological and hydrogeological conceptualisation of the area was first done in late 2000, based on data from more than 4244 bores (from 5m to more than 800m depth).

However, given the abundance of data, the PIWI project illustrated how groundwater system conceptualisation can be notably altered based on repurposing available data; this was achieved by adopting new techniques to analyse existing large data sets, in addition to new data acquisition such as seismic and airborne electromagnetic (AEM) surveys, environmental tracers, and aquifer barometric efficiency. The new findings include: 

  • The 500 m wide Serpentine fault zone was characterised as a hydraulic boundary for the east–west groundwater flux. It separates the groundwater system into two markedly different sub-regions, with unique hydrogeochemical signatures, levels of confinement, and groundwater flux directions.
  • A complex architecture of the groundwater system was identified in the eastern sub-region where spatially constrained sandy formations were mapped below 100m depth, which may form an aquifer.
  • The three-dimensional lithological model developed within the project allowed a 3D representation of the aquifer’s hydraulic properties (i.e. a 3D data cube).
  • The conceptualisation of regional groundwater flow was re-evaluated due to discover of a saline wedge under the river channel, which forms one of the project area boundary.

The results allowed to close previously identified knowledge gaps (fault existence) and unearthed previously unknown features (e.g. hydrogeological architecture of the eastern sub-region). The updated conceptual model reduces uncertainties in a decision-making process.