Risks to the GAB

Pilliga gas well

A paper published by the CSIRO in 2011 stated that ‘mining, manufacturing, and other industries use about 20% of all water consumed in Australia’. It recognised the fast growing mining industry, the risks it posed by discharging large quantities of water into the environment, and the resulting water management challenges.

Rob Banks’ outlines some of the risks to the Great Artesian Basin in an executive summary in his report on the Great Artesian Basin, published in December 2014.

Typically CSG production involves dewatering (pumping) of coal seams to allow methane gas to be extracted (the water is a waste product of production called produced water). There is proven downwards connection between sub basins of the GAB and many of its underlying petrochemical rich basins (Surat has 10% connection; Eromanga has up to 50% connection). It follows that dewatering of aquifers under the GAB where proven connectivity exists can ultimately reduce pressure heads in the critical recharge areas of the GAB and reduce or halt water flow at its numerous bores and springs. (SoilFutures Report, p. 4)

This report shows that the proliferation of gas exploration and production licenses on recharge zones appears to have progressed without much consideration of a GAB wide impact on artesian groundwater resources and pressures. Regulation which is GAB wide and transgresses state boundaries should be considered particularly with regard to protection and management of the few and critical recharge areas of the GAB.

Clearly, there are other wide ranging risks to the water supply of the GAB, with many free flowing bores still in existence (which causes local water and pressure depletion), as well as large scale uranium mining in South Australia. None of these other risks have the potential to stop groundwater flowing across entire sub basins within the GAB.

Rob’s report contains a series of maps showing the Great Artesian Basin’s recharge areas and the areas covered by petroleum exploration or production licenses at that time of publication.

The data in Figure 7, show that 1.38 million km2 (or 80% of the GAB) is taken up with exploration or production licenses associated with gas or petroleum. (SoilFutures Report, p. 14)

The northern gas fields in the Surat Basin in Queensland are located in critical recharge areas of the GAB, as is Santos’ CSG Narrabri project in the East Pilliga area of NSW.

In NSW the recharge areas of higher than 5 mm/yr and >30 mm are almost entirely contained within the east Pilliga area. (SoilFutures Report, p. 13)

The First Edition of Rob’s report was presented to the NSW Minister for Water by the NSW Artesian Bore Water Users Association on the 7th November, 2014. One of the immediate criticisms of the document was lack of transparent peer review. A Revised Edition was published with clear peer review references and presented to the NSW Minister for Water on 5th December 2014. The NSW Department of Primary Industries Office of Water’s unsigned and undated three page review is published in Appendix 1 of the report. A summary of criticisms and the authors response is in Appendix 2 and includes the following –

The main issue raised in the report is that of risk to pressure heads which drive the GAB through extraction of waters in aquifers beneath the GAB which are partially connected to the GAB. There appears to be no dispute on behalf of the reviewer over this issue. (SoilFuturesReport, p. 26)

The conclusion of the report is that the highly localised critical recharge areas identified are the only places where the significant recharge waters can get into the GAB. Potential lowering the hydraulic head in these critical areas is therefore important. This is not held in dispute in the NSW Minster for Water’s review.

References:

Water in mining and industry by Ian Prosser, Leif Wolf, and Anna Littleboy 

Great Artesian Basin RechargeSystems and Extent of Petroleum and Gas Leases, 2011, SoilFutures Consulting Pty Ltd for the Artesian Bore Water Users Association. 

     Maps with production or petroleum exploration licences in GAB and recharge areas

     See pages 14-15