Throughout the last 110 years, water has been extracted from aquifers of the GAB through bores. Due to loss of pressure, approximately one third of the original artesian bores have ceased to flow, and more than 1,000 natural springs (and their ecosystems) have been lost. However, the GAB remains one of a few major artesian basins in the world that have not been severely over exploited.
Late in 2014, the Great Artesian Basin Coordinating Committee (GABCC) requested government jurisdictions to compile data on the age of all bore assets and drilling within and through the GAB, as useful inputs in developing the new draft GAB Strategic Management Plan (SMP).
The report ‘Summary of past drilling activity within the Great Artesian Basin’ is a statistical compilation from data archives in New South Wales, Queensland, South Australia and the Northern Territory. This is the first comprehensive statistical summary of the status of all bores within the GAB. It is expected to be updated regularly, at least every 5 years to align with on-going review of the SMP.
The report presents updated and improved information on the magnitude of long-term maintenance requirements for bores, a realistic assessment of their replacement value, and risks to the groundwater resource of not continuing investment in infrastructure maintenance and renewal.
The report includes bores or wells for: water supply, monitoring and exploration of groundwater; exploration for coal; exploration and production of conventional gas, unconventional gas and petroleum; geothermal energy; and mineral exploration. Not included are shallow bores in sediments overlying the GAB, such as Tertiary and Quaternary alluvium associated with present day river systems.
Preliminary Conclusions from bore data – priority risks
A high risk of bore failure arises from those drilled prior to 1960, before pressure cementing of water supply bores was widely adopted. These may pose a risk of leakage between aquifers if casings fail. Their status and maintenance needs are yet to be determined. The significant level of investment to date to access GAB water needs to be continuously maintained and the statistical results of the report provide an indication of the priority of risk areas for future focus.
Great Artesian Basin Bore Data Report Factsheet
A short summary of statistics generated by the Bore Data Report
Total number of bores drilled into and through the GAB, including recharge and non-artesian areas; 75% of these are for water supply
Number of water supply bores drilled in artesian or previously artesian areas; 2,748 of these were drilled before 1960, prior to requirements to cap flowing supplies, and therefore likely to be at higher risk of failure
Number of bores rehabilitated under the GABSI program since 2001
Kilometres of bore drain replaced with piping under GABSI
Estimated annual water saving (millions of litres) resulting from GABSI capping and piping
Remaining bores with uncontrolled flow (at 2015); of these, about 463 (87%) were constructed prior to 1960 #
Estimated replacement cost of all water supply bores
Estimated replacement cost of deeper, higher pressure water supply bores (excludes bores less than 200m deep)
# Changes in flow in artesian bores as a result of capping programs are difficult to compile without a comprehensive census. Many of these wells have small surface flows but may have flow loss below surface.