In a transcript from the inquiry into the implications for Western Australia of hydraulic fracturing for unconventional gas, Water Corporation planning and capability group general manager Ashley Vincent said there was a risk in the Perth Basin that fraccing operations could threaten an aquifer system running from Geraldton to Busselton.

However, he said proper regulation could protect WA's water resources while allowing unconventional gas resources to be exploited.

The Australian Greens have leapt onto the issue, claiming the WA Mines and Petroleum Minister Bill Marmion should be forced to drinking fraccing fluid in light of the Water Corporation's warning.

However, industry group the Australian Petroleum Production and Exploration Association believes WA's existing risk-based regulatory regime is sufficient to protect the state's drinking water supplies.

In his evidence to the inquiry on February 10, Vincent said there were few areas in the Perth Basin where the search for unconventional gas would impinge on the state's water supplies.

"Looking at the blow-out [map] of the Perth Basin, the actual areas of overlap of existing public drinking water sources is very small but recognising that they are significant sources that supply the metropolitan scheme, it is important they are recognised and protected, is our view," he said.

In a submission to the inquiry Vincent says unconventional gas exploration should not occur in public drinking water supply areas and calls for a 1.5km exclusion zone around PDWSAs.

However, when pressed by the inquiry, he could not provide any scientific source for the 1.5km zone other than to say: "I think it provides a safeguard for any surface movement, any surface drainage and, you know, any water movements like that.

"It also provides recognition of the fact that unconventional gas happens in three dimensions, it is not purely vertical, it does move into the horizontal, and provides a level of protection.

"These things are never perfect but it recognises the need to provide some additional safeguards for those specific potentialities I guess."

Vincent said unconventional gas development had the potential to contribute to WA's social and economic development.

He said proper regulation could ensure the unconventional gas industry could be developed and WA's drinking water stocks be protected.

"The public drinking water supply in WA is governed by a sound regulatory framework that has served the state and communities well over a long time frame," Vincent said.

"We believe there is an excellent opportunity to formally recognise this drinking water management framework in the context of regulation and the operation of unconventional gas projects and, secondly, that the corporation is allowed to be an active participant in the referral, assessment and environmental management planning of these projects."

Australian Greens Senator Scott Ludlam used news of the Water Corporation's warning to call on Marmion to honour his commitment to drink fraccing fluid.

"Now the government's own Water Corporation is warning fraccing could contaminate our drinking water, we want to know if Minister Marmion is still confident enough to drink fraccing fluid as he said he would last year," Ludlam said.

"Our drinking water is too important to risk with fraccing, especially when we've seen it threaten water supplies in other states with uranium and asbestos contamination."

APPEA western region chief operating officer Stedman Ellis said existing regulations were sufficient to protect WA's drinking water.

"This view was recently endorsed by Mines and Petroleum Minister Bill Marmion when he rejected calls for fraccing to be banned near public drinking water as unnecessary," Ellis said.

"Under the existing regulatory framework, any activity which is likely to impact on public drinking water areas faces multiple levels of assessment and approval.

"Activities near water resources are automatically referred to the Environmental Protection Authority for assessment under the state's strict environmental protection legislation.

"The minister for mines and petroleum can also seek advice from the minister for water as to whether the proposed activity is acceptable."