Groundwater quality

A clean and safe supply of groundwater is essential for the drinking water needs of country towns, major industries (especially agriculture) and to support groundwater dependent ecosystems. Groundwater quality decline and contamination creates a serious threat to human and animal health and the degradation of wetlands and rivers.

Groundwater quality protection is achieved through the consideration of both the Objects and Principles of the Water Management Act 2000. These Objects and Principles must be considered for all new or replacement groundwater works. Approvals for: water trading, agency submissions into NSW State Significant Development project proposals and during the development of policy documents such as the Aquifer Interference Policy, 2012 (PDF, 505.49 KB). Where an activity has potential to degrade water sources, dependent ecosystems (including groundwater and wetlands), DoI Water reserves the right to refuse licence or works approval, or can direct modifications to the proposal occur to achieve minimal cumulative impact.

On a national level, guidelines have been developed to provide a framework for protecting groundwater contamination in Australia and are part of the National Water Quality Management Strategy. The protection framework involves the identification of the specific beneficial uses of every major aquifer with strategies which can be applied to protect those beneficial uses.

A particular risk to groundwater sources is contamination by leakage into the water table of pollutants from: industrial sites, fuel storage tanks, septic systems, land fill sites, garbage dumps, abattoirs, cattle feedlots and piggeries. The Office of Environment and Heritage is the lead agency responsible for managing contaminated groundwater and developing groundwater clean-up strategies for contaminated sites. The NSW DoI—Water assists by supplying technical information, establishing the beneficial use of aquifer systems and restricting the take of groundwater (if necessary).

Botany Bay area has numerous contaminated sites and the department has developed a management approach for the Botany Bay sand aquifers.

Per and poly-fluoroalkyl substances (PFAS) contaminants in NSW have become an emerging groundwater issue in recent years over concern to human health and the environment, particularly due to their persistence and bioaccumulation. PFAS have been used in many applications including firefighting foams, textile treatments for upholstery and clothing, paper products and non-stick cookware. Due to the multiple pathways for PFAS exposure a coordinating government response is needed to manage risk. NSW EPA is the lead agency who coordinate an inter-agency PFAS advisory group, including DoI Water.  PFAS investigation sites across NSW along with the current knowledge and progress of remediation works is available on via EPA’s website.  In addition, Australia’s Environment Ministers have endorsed the country’s first PFAS National Environmental Management Plan (NEMP). The PFAS NEMP provides governments with a consistent, practical, risk-based framework for the environmental regulation of PFAS-contaminated materials and sites.

Characterisation of hydrogeochemistry and risks to groundwater quality

The National Water Commission and the department funded a large scale investigation into the chemical characteristics of groundwater to improve our understanding of the possible impacts of high volume groundwater pumping on groundwater quality.

The studies, undertaken in collaboration with consultant Parsons Brinckerhoff, took place in the high-yielding aquifers of the Namoi, Macquarie, Lachlan, Murrumbidgee and Murray valleys, all within the NSW part of the Murray-Darling Basin. Over one thousand groundwater samples were taken from government-owned monitoring bores and private production bores.

To understand the processes affecting groundwater salinity, a broad range of chemicals were analysed including major ions, trace elements, nutrients and stable isotopes. The results were studied to characterise the chemical make-up of the water, assess where the groundwater was recharged from and analyse aquifer mixing processes. Spatial and temporal trends were identified, an assessment made of the beneficial use of the water and any areas at risk to groundwater quality deterioration were identified.

The results of this study were used to strategically refine the department's groundwater monitoring program to focus on areas where groundwater quality deterioration was found, while keeping a broad eye on groundwater quality in other important high-use locations.

Groundwater vulnerability maps

A valuable tool used for groundwater quality protection is 'groundwater vulnerability mapping'. These maps show the vulnerability (or level of risk) of aquifers to contamination relating to physical characteristics of the location, such as the depth to the water table and soil type. The maps should be used by groundwater managers, planners, developers, and regulating agencies to make better informed judgements on where to locate potentially polluting activities so as to minimise the risk to groundwater.

Groundwater vulnerability maps are available for a number of catchments in NSW. These maps are accompanied by explanatory notes to guide their use and explain how the maps were created.