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Background

 

Saltwater-freshwater interface in a
typical coastal aquifer
© Geoscience Australia

In Australia’s coastal fringe, continuing population expansion combined with significant reductions in rainfall in many coastal catchments have led to an increasing dependency on these coastal groundwater resources. Although the situation varies across the country, there is evidence of over-use in several major Australian coastal aquifers.

One consequence of the over-use of coastal groundwater resources is the increased risk of salinisation of aquifers through the encroachment of seawater. To date, there has not been a comprehensive seawater intrusion (SWI) vulnerability assessment at a national-scale, although the need for such an assessment has been recognised.

Geoscience Australia is currently undertaking a national-scale vulnerability assessment of coastal aquifers to seawater intrusion in collaboration with the National Centre for Groundwater Research and Training (NCGRT) as well as state and territory water agencies. Project funding has been provided through the Raising National Water Standards program which is administered by the National Water Commission.

Objectives

The principle aim of the project is to identify the coastal groundwater resources currently vulnerable to seawater intrusion and potentially at risk as a result of over-extraction, sea-level rise and/or recharge-discharge variations associated with climate change.

Expected outcomes

The expected outcomes of this project are:

• an audit of existing SWI investigations and research in Australia
• a GIS-based compilation of hydrogeological and other key datasets relevant to a national-scale SWI vulnerability investigation
• the identification of knowledge and data gaps for SWI vulnerability assessment
• the development of a typological classification including generic conceptual models that are representative of typical Australian coastal aquifer systems
• an evaluation of vulnerability factors and trends
• the development of a series of 1D sharp-interface, analytical models applied to highly idealised representations of a range of typical coastal aquifer settings
• a greater understanding of the sensitivity of hydrogeological parameters and boundary conditions on the behaviour of the freshwater-saltwater interface
• the development of a series of national-scale, GIS-based maps of SWI vulnerability.

Project implementation

The project will be conducted in three phases:

Phase 1: literature review and baseline assessment
Phase 2: conceptualisation and vulnerability methodology design
Phase 3: vulnerability assessment and mapping.