The Queensland Water Commission’s independent analysis of expected cumulative impacts from Coal Seam Gas developments suggests that 528 individual bores in Southern Queensland will experience declines by more than trigger threshold levels.
The Queensland Government declared the Surat and southern Bowen Basin a Cumulative Management Area which gave the Queensland Water Commission the responsibility of preparing an Underground Water Impact Report.
21,000 bores are included within the Surat CMA area, used for grazing, irrigation, industrial and urban consumption.
Coal Seam Gas companies are expected to extract 95,000 megalitres of water per year over the life of the industry, the QWC says. “This extraction will impact on water levels.”
Of the existing bores in the Surat CMA, the QWC believes 528 are expected to experience a decline in water levels of more than the 5m trigger threshold due to CSG water extraction.
Of that number, 85 are expected to see water levels decline by more than trigger threshold levels within the next three years.
The depth of the expected impact varies depending on aquifer.
In the Walloon Coal Measures, the target formation for CSG operations in the Surat Basin, the long term impact for most is expected to be less than 150m. In the more westerly areas, the impacts are expected to be up to 700m. 400 private water bores source water from the formation in the affected area, however half were likely to experience an impact of less than 21m, the QWC draft report predicts.
In the Bandanna Formation, the target formation for CSG operations in the Bowen Basin, the long term impact is expected to be less than 200m, but up to 1000m in places. “However, in areas where private bores tap the formation, the impacts are expected to be much smaller,” The QWC draft report states. “It is expected the impacts will not exceed 5m in any bore”.
Water levels in other sandstone formations lying over or below the Walloon and Bandanna formations are predicted to fall by varying amounts, however in most cases the QWC does not believe bores sourcing water from these aquifers will fall below trigger thresholds.
It expects maximum impacts of water drawdowns to occur towards the end of the life of the industry, generally between 2030 and 2075.
The QWC says a regional water monitoring network with 498 monitoring points will be put in place to gather data on water levels and quality.
The QWC also noted that its analysis does not take into account any re-use or reinjection of CSG water which has the potential to mitigate the impact of CSG water extraction on water levels in aquifers.
Landholders in the Surat Cumulative Management Area can view the Queensland Water Commission's draft Underground Water Impact Report for the Surat CMA in detail on the QWC's website by clicking here
The report is open for public comment until 5pm on June 22, 2012. Details on regional information sessions, and how to make submissions during the consultation process, are also available at the above link.