The 15 bores, which connect to the deep water of the Gunnedah-Oxley Basin, were referenced in Santos' original Groundwater Impact Assessment.

But there is no mention of them in the Planning Department's recent 392-page assessment of the project.

Much of the assessment focused on the productive shallow aquifers of the region which most farmers use - the Namoi Alluvium and the Pilliga Sandstone - and the degree in which they would be affected by depressurisation and dewatering.

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But Gunnedah-Oxley Basin water user Mal Donaldson said the Planning Department had totally overlooked the threat the gasfield posed to his and other nearby farmers' water supplies.

There are naturally-occurring high levels of methane in one of Mr Donaldson's bores, which he said indicated a likely connection between the coal seams Santos was targeting, and the basin.

"I am seriously concerned that should Santos' destructive gas field go ahead, my water bore will become a gas bore," Mr Donaldson said.

"My father had this bore drilled over nine months in 1953-54, yet the Planning Department behaves like it doesn't exist.

"This is an insult to farmers in this region - we exist, our farms exist and they rely on this water."

The Planning Department's Water Expert Panel (WEP) stated to the conclusion that "the risk of gas migration into groundwater bores is low" and "the risk of induced and enhanced aquifer connectivity via groundwater and CSG production bores is very low".

However, Mr Donaldson questioned how the WEP came to that conclusion without examining his bores.

He hopes the Independent Planning Commission (IPC), which is about to commence two weeks of public hearings before giving a final verdict, will listen to his concerns.

"If the IPC ignores us too, it could have far reaching, negative implications for us," Mr Donaldson said.

The Planning Department Water Division's own assessment made it clear the model used by Santos couldn't not predict impacts on landholder's bores and it had "limited information about water supply works is available for the Gunnedah-Oxley Basin".

The WEP also advised the model used by Santos had "poor predictive capacity in relation to the impact of production of the surrounding impacted water sources", which means water users may be left high and dry.

The Planning Department did not answer The Land's questions about why the bores were left out of its assessment or how many bores it physically surveyed with boots-on-the-ground staff.

It instead defended its assessment of the project, which was "based on consideration of a range of detailed reports, groundwater modelling and expert advice".

"The Water Expert Panel and the NSW government found that the risks of the project on water resources are able to be effectively managed and are unlikely to result in any significant impacts to regional land and water resources," a department spokesperson said.

Lock the Gate NSW coordinator Georgina Woods urged the IPC to pay particular attention to the plight of the farmers east of the Pilliga when it considers Santos' proposal at the end of the month.

"After battling an unprecedented drought for years, the Planning Department's omission is yet another blow for farmers in this district," Ms Woods said.

"It is not good enough to let Santos proceed with this gasfield on the basis of closing your eyes and hoping she'll be right.

"These farmers could lose their water if this gasfield is allowed to go ahead. No one in Government so far has stood up for them and made Santos find out what the impact on them will be.

"The IPC needs to hear what they have to say."