Groundwater: the natural wonder that needs protecting from coal seam gas

Recent reports of leaking wastewater ponds and pipelines at Santos' Narribri gas project in New South Wales have heightened concerns about the impacts of coal seam gas extraction on groundwater.

The project could see drilling of up to 850 wells in the Pilliga Forest of northwest NSW and has drawn strong resistance from local land owners and environment groups.

Following one leak Santos reported higher levels of salts, heavy metals and uranium in groundwater. However on investigation the NSW Environment Protection Authority concluded there was not enough evidence to link the higher levels with the wastewater leaks. Santos has been cautioned and required to develop pollution reduction programs.

In a separate 2013 incident Santos was fined A$1,500 for pollution at another well site in the Pilliga.

The problems have mainly occurred due to mistakes during the storage and transport of coal seam gas wastewater, produced in high volumes as a by-product of gas well development. The fact that multiple incidents have occurred while the project is still in very early stages with only a handful of exploration wells drilled, gives weight to the argument that the risks to groundwater might outweigh the potential benefits.

There is arguably even greater cause for concern about the effects of this particular project on Australia’s precious groundwater, due to a coincidence of geology.

The Great Artesian Basin is ‘recharged’ through areas such as the Pilliga in New South Wales.Matthew Currell

Groundwater’s headwaters

The Pilliga Forest is located above one of the few areas known to provide groundwater recharge to the Great Artesian Basin - Australia’s largest and most important groundwater system.

This was shown in the recent water resource assessment by CSIRO, and in a subsequent report produced last year by SoilFutures Consulting.

The Pilliga is one of only a handful of recharge areas providing significant new water to replenish the stores within this vital groundwater system. The basin has been described as one of the seven hydrogeological wonders of the world, and it supports a rich and diverse set of groundwater-dependent ecosystems, as well as thousands of rural Australians living off the land.

A recharge area is the location where groundwater first infiltrates into the geological layers that form the aquifers in a groundwater system. Usually these areas are restricted to small geographical zones at the edges of a geological basin, where the land is elevated and the aquifers exposed at the surface.

Rainwater infiltrating at these areas continually replenishes the aquifers with new water. Recharge areas can therefore be compared to the “headwaters” of a river-catchment, as they provide all the water that flows onwards through the rest of the system. Just like in a river catchment, the protection of water quality in these areas is of critical importance not just to the local environment, but to the whole system.

A recharge area also plays an important role in maintaining aquifer pressures, and therefore water levels throughout a groundwater system.

Protecting groundwater

Due to its current status as a nature reserve, the Pilliga Forest is probably the most pristine of all the recharge areas feeding water to the Great Artesian Basin.

If groundwater is contaminated or pressure is lost in this area, then there is the risk of having widespread effects on groundwater quality and quantity that are not just local in their impact (as would be the case in most other locations).

This is why I believe the Pilliga should be set aside as a strategic “groundwater recharge protection zone”, to ensure the long-term health of the basin.

In Europe and North America, it is common for governments to set aside recharge areas, like the Pilliga, as “groundwater well-head protection zones”. This is based on the recognition that pollution of these areas can have a widespread impact on the whole groundwater system. Land-use activities like forestry or use of fertilizers and petsicides are typically banned in well-head protection zones.

There is no reason Australia could not institute similar arrangements, banning potentially risky activities like coal seam gas development in important recharge areas.

Proceed with caution

Some landowners in the Pilliga depend on groundwater as their sole source of potable water, while thousands more in areas to the north and west depend on groundwater recharge being maintained for their livelihoods.

This is why the NSW government and Santos need to carefully consider whether the potential risks of coal seam gas development in the area outweigh the potential benefits.

If already groundwater is being contaminated with salts and metals after only a handful of wells have been drilled, it is likely that up-scaling the project will lead to more contamination, which could impact the Great Artesian Basin’s water for generations to come.

As we enter another El Niño period, which last time brought extreme drought that crippled farming communities, policy makers would do well to consider the strategic importance of protecting our country’s precious groundwater, particularly in recharge areas like the Pilliga. Long after the gas rush ends, farms and ecosystems will still be depending on Australia’s scarce and precious water supplies.

Matthew Currell receives funding from the Victorian Department of Environment, Land, Water and Planning for research into baseline groundwater chemistry and isotopes in areas of potential gas development