A Queensland government technical study has acknowledged for the first time that subsidence caused by coal seam gas drilling could have potential consequences for farmers in the fertile Darling Downs.
Relationships between some farmers and CSG companies have become strained in the past few years, amid claims that one company, Arrow Energy, drilled diagonally beneath farmland without notifying landholders.
Arrow was fined $1m last month for breaching land access rules.
Guardian Australia has previously reported on concerns that Queensland has allowed the rapid expansion of the CSG industry before the long-term effects were properly understood; that the law ascribes no environmental value to farmland; and that landholders have little recourse in the event CSG drilling causes subsidence on their properties.
Gas companies and the state government have previously acknowledged that subsidence would occur as a result of drilling. But for the first time, in an update to the regional Underground Water Impact Report, the state has noted that farming practices could be affected as a result.
Farmers in the Darling Downs say that even minuscule changes to the flat black soil plains could disrupt soil drainage and farming methods like laser-levelled cropping, a practice that can increase yields, save water and reduce fertiliser use.
In 2020, the Queensland Office of Groundwater Impact Assessment spoke with landholders about potential consequences of subsidence on farming. The report says that concerns focused on changes to ground slope that “could affect surface water drainage directions and have implications for irrigation and other farming practices”.
The report included state modelling of subsidence, and estimated 10cm of subsidence has already occurred in some areas. It concluded subsidence of about 15cm could occur in some farming areas near Cecil Plains, and up to 17.5cm in areas around heavily developed CSG fields.
“Subsidence may, depending upon the magnitude and rate of change over time, potentially affect the ground slope of irrigated cropping land and hence the irrigation practices,” the report says.
It also suggests the maximum change in ground slope from CSG-induced subsidence in most areas would be less than 0.001% (10mm over one kilometre).
Zena Ronnfeldt, a farmer from the Dalby area who first discovered Arrow Energy had drilled diagonally beneath her land without notifying her, said the report did not paint the full picture.
She claims subsidence has occurred on one of her paddocks, affecting the drainage and ultimately the crop yield, as a result of CSG drilling.
Ronnfeldt said the report uses averages from a large dataset, and that it would not “pick up the irregular patches of subsidence that are happening over time, including on our property”.
“It’s impacting our land because it is not uniform. Averages mean nothing when you’re out there in the paddock on a machine that’s become bogged while trying to conduct farming operations.”
The report found that more than 700 water bores would be affected by CSG operations. That figure has risen from 459 in 2016.
Queensland spokesperson for the Lock the Gate alliance, Ellie Smith, said each successive state Underground Water Impact Report had shown the impact of CSG on groundwater and farmland was worsening.
“The dramatic increase in the number of water bores predicted to be drained shows the government is behind the eight ball,” Smith said.
“The green light was given, and continues to be given, to the voracious coal seam gas industry without a thorough understanding of how it threatens farmland and groundwater across the Western Downs.”
