Anti-coal seam gas campaigners last week seized on a new report warning of "catastrophic pressure losses" in "numerous bores and springs" resulting from the company's activities.

The report's author, Robert Banks, who was commissioned by the Artesian Bore Water Users Association, said the Pilliga was the basin's most important "recharge" area.

The basin covers an estimated 22 per cent of mainland Australia and provides many inland areas with their only reliable source of fresh ground and surface water.

However, the oil and gas giant has dismissed the notion that the "de-watering" of coals seams, essential for extracting the gas, will harm the basin.

"Our groundwater modelling shows that de-watering or depressurisation of our coals has a negligible effect on the GAB," Santos hydrogeologist Glenn Toogood said.

"Essentially, the GAB is a separate groundwater system to the coals which we target ... it is hydraulically disconnected from our coals."

Mr Toogood said Santos would need to pay for the water an average of about 1.5 gigalitres a year it extracted from the Gunnedah-Oxley Basin during its operations.

According to Santos, 1.5 gigalitres or 1.5 billion litres is roughly the amount of water needed to annually irrigate 250ha of cotton.

"We are very confident that our de-watering doesn't have an effect on people's water, or ability to use water from the GAB," Mr Toogood said.

Santos is continuing to work on the environmental impact statement for its $2 billion Narrabri Gas Project, which could supply up to 50 per cent of the state's gas needs.