Groundwater is the water beneath the earth's surface which filters through and is held in rock, gravel or sand. Groundwater can be found in all areas of NSW, although its quantity and quality vary widely. An aquifer is a geological formation such as permeable rock or unconsolidated material (gravel, sand silt or clay known as alluvium) which can hold groundwater.

An important natural resource in NSW, groundwater is a source of drinking water for many rural towns and is used for industrial needs such as mining. It also supports the domestic and stock requirements of farms or remote households and communities, and can be used for irrigation. While water availability in a river can change very quickly because of rainfall or dry conditions, groundwater availability is more stable.

Groundwater is most commonly accessed by bores or wells. Of all water use in NSW, 11 per cent is sourced from groundwater. The Office of Water is responsible for the management of groundwater resources in NSW.

Until relatively recently, management of the state's groundwater resources was generally focused on investigation and subsequent development. Little attention was paid to the impacts that extraction might have on its continuing availability and the possible impacts on the environment.

The NSW State Groundwater Policy Framework Document (PDF 2 MB) highlights the need to manage the access to groundwater within the sustainable yield of a system so that the availability of the resource is sustained for all consumptive uses as well as the dependent ecological processes. Sustainable groundwater management also requires the protection of water quality and groundwater dependent ecosystems.

Most groundwater in NSW is sourced from groundwater systems covered by water sharing plans. Partly or fully buried groundwater sources have little or no surface expression (outcrop), and therefore have very little or no water available for extraction based on rainfall recharge. The NSW policy for managing access to buried groundwater sources (PDF 2 MB) presents a framework for allowing access to a small percentage of groundwater storage in specified porous rock groundwater sources, subject to certain criteria being met.

Groundwater trading rules are established by the relevant water sharing plan in areas covered by the Water Management Act 2000. For access to new licences for groundwater in areas still under the Water Act 1912, a licence application under may be lodged, subject to any embargo order applying to that area.

Monitoring groundwater

The NSW Office of Water undertakes drilling to investigate the states' groundwater resources. The Office of water has more than 3000 monitoring bores and uses computer-based groundwater modelling to better understand groundwater flow systems.

Expanding our networks

The Office of Water is increasing the spatial coverage of our monitoring bore network through the drilling of new groundwater bores in key areas of NSW between August and December 2013. The three areas of construction are Gunnedah to Spring Ridge, Broke-Bulga and Merriwa. Download the factsheets below for more information:

NSW groundwater works

NSW groundwater work details provide preformatted reports (borehole logs) containing information about licensed water bores, wells and excavations. Please note there is a slight delay while this application is loading.

For information about obtaining a licence for a groundwater works (licensed water bores, wells and excavations) please go to Licensing under the Water Act 1912.

Groundwater status reports

The Office of Water is producing a series of status reports on the state's groundwater resources. These reports describe the physical state of the resources for different areas, provide information on groundwater licensing and use, and discuss the response of the groundwater system to variability in groundwater use and rainfall.

Groundwater sources summary reports

The Office of Water is producing a series of annual summary reports on the state's groundwater sources describing water sharing plan provisions, available water determinations, account management rules and groundwater trading. These reports will include up to date information on access licences, water account information, trade statistics, groundwater extractions and water levels.

Resource condition assessment reports

The Office of Water undertakes risk assessments following the implementation of a water sharing plan.

Groundwater trading and management of local impacts reports

These reports provide information on trade assessment rules, established local impact areas and in-house tools developed to manage groundwater extractions at a local level.

Thirlmere Lakes groundwater assessment

Thirlmere Lakes Drilling Report Figures

The NSW Office of Water has undertaken an assessment of the possible causes of water level decline reported for Thirlmere Lakes in recent times.

Various lines of evidence have been considered to establish the likely cause of the reported water level decline. These have included consideration of Tahmoor Colliery operations, long-term rainfall records, broader catchment river flow data and regional groundwater levels.

No hydrology data exists for the lakes themselves, however the local and region hydrology data that is available indicates that the most likely cause of the reported water level declines in Thirlmere Lakes is due primarily to the prevailing climatic conditions. Specifically the continuing declining trend in rainfall, established during the recent severe drought, appears to be affecting on surface water runoff and recharge to groundwater. This trend needs to be reversed by extensive and protracted rainfall events before recovery in flows and lake levels can be observed.

As a result of this investigation, there was no evidence to suggest that mine fracturing or subsidence has affected the water levels in Thirlmere Lakes in any substantial way.

Read the full report: Thirlmere Lakes groundwater assessment (PDF 7.4 MB).

Thirlmere Lakes drilling project

The NSW Office of Water has completed the drilling of four groundwater monitoring bores in the vicinity of three of the five Thirlmere Lakes at the Thirlmere Lakes National Park. Drilling was undertaken to address one of the data gaps identified by the NSW Office of Water in a groundwater assessment report published in December 2010. The lack of a groundwater monitoring record in the vicinity of the lakes has been a significant missing element in understanding the Thirlmere Lakes hydrogeologic environment.

Thirlmere Lakes drilling report

The results of the completed drilling project have been documented in the Thirlmere Lakes drilling report (PDF 8 MB. Please note this will take 19 minutes to download at 56 Kbps). The report details the drilling and construction of the monitoring bores completed during May and June 2011. About 190 linear metres of drilling was successfully completed, of which samples have been collected for future research projects. A copy of the report was provided to the Thirlmere Lakes Independent Inquiry Committee.

The drilling will not result in immediate answers to the problem of declining water levels in the lakes, but the monitoring bores will be used to collect long-term information for future interpretation.

Additional works relating to the monitoring of lake levels and rainfall within the lakes catchment will be needed to complete the picture. The monitoring bores will provide evidence of groundwater level trends over the long-term as a progressive record of automatic data is gathered.