BRISBANE, AAP – Groundwater extraction by Queensland’s expanding coal seam gas industry is expected to peak at the equivalent of 48,000 Olympic swimming pools annually within the next decade, a report has found.

Gas is the “dominant and expanding” resource in the Surat and Bowen basins that cover large swaths of land in the southeast and central parts of the state.

There are about 8600 wells in place, and the number is expected to expand to 22,000 based on current projections.

Predicted impacts are broadly similar to those flagged in 2019, with a marginal increase in water extraction from CGS activity, the draft report prepared by the Independent Office of Groundwater Impact Assessment says.

There has been a “significant increase” in associated water extraction by CSG since 2014, to the current level of around 54,000 megalitres per year from about 8600 wells, it says.

Extraction is expected to peak in 2027, with about 120,000 megalitres extracted, while predicted extraction in the next three years is likely to be around 80,000 megalitres per year.

The process of gas extraction involves drilling a well in the coal formation and extracting groundwater, resulting in depressurisation.

The rate of water extraction is high in the early stages, then gradually declines as the target pressure is reached and gas flow increases.

“In a CSG field, multiple wells are constructed about 700-1000 metres apart from one another to depressurise large parts of the formation,” the report notes.

The coal mining footprint is less than two per cent of CSG in the region, and currently extracts less than 1000 megalitres of groundwater annually.

“This is the first time the report cumulatively integrates coal mining impacts with CSG impacts, OGIA executive director Sanjeev Pandey says.

It also predicts hundreds of metres of groundwater pressure decline in target formations, and some impacts in aquifers as a result of the 22,000 projected CSG wells.

As well as fossil fuel extraction, groundwater from bores in the region is used for farming and domestic use.

More than 700 water bores are predicted to be impacted in the long term, 108 of which in the next three years.

Strategies to manage the impact of resource development include “make good” agreements for affected bore owners, mitigation actions for springs and watercourses, and a “comprehensive” monitoring network.

The underground water impact report is prepared every three years, and public information sessions for affected communities will be held next month.