A New South Wales coal mine is being accused of inappropriately taking more surface water than it is entitled to.

A review of Whitehaven Coal's Maules Creek Mine near Narrabri by the campaign group Lock the Gate showed it captured 1,800 million litres (ML) of surface water in 2016, despite being licenced to take 30 million litres.

Surface water is water that is collected from rainfall and run off.

An examination of surface water licences in New South Wales has been unable to find any other surface water licences held by the mine to justify the additional water.

"It does appear that the take is much higher than the licence they have explained to the community," Maules Creek farmer Lochie Leitch said.

Whitehaven Coal declined to be interviewed.

The company issued a statement saying it was in compliance with its water licences, and the use of rainfall and runoff is permissible under legislation.

'Dirty water' a license exemption

Farmers whose properties neighbour the mine have joined forces with the campaign group, Lock the Gate Alliance, to lodge a complaint with the state's new water watchdog, the Natural Resources Access Regulator.

The NRAR was set up in April 2018 following a review of water management and compliance which was prompted by a story by the ABC's Four Corners.

The farmers are worried that the alleged collection of this extra surface water is affecting the environment.

"[It's] simply capturing too much water that would otherwise be recharging groundwater and flowing into surface water systems," Maules Creek farmer Sally Hunter said.

Maules Creek farmer Sally Hunter is worried about Maules Creek Mine's collection and use of surface water. ( ABC News: Elena De Bruijne )

The complaint centres on the alleged unlicensed take of surface water by Maules Creek Mine, the rules governing the use of water, and exemptions within the Water Management Regulation 2011.

One of the exemptions relates to dirty water, which is water that is collected from mining areas.

It does not require a water access licence because the water can be contaminated.

Carmel Flint from the Lock the Gate Alliance said this exemption had been misused.

"We certainly don't believe that exemption should be available to the mining industry," Ms Flint said.

"If they're taking vast quantities of water that should be in our creeks and our rivers, then they should be subject to the same rules as the agricultural industry."

The Maules Creek mine site is adjacent to farmland. ( Supplied, file photo )

The Environmental Defenders' Office (EDO) has lodged the complaint with the NRAR.

"The critical part about that is that that water can't be used, and we understand the policy reasons behind that is that if you allow a operator to use that dirty water it actually provides an incentive for that operator to make it dirty," senior EDO solicitor Rana Koroglu said.

"We believe this has the potential to be an important test case for the regulator, especially as there is evidence, the company's own evidence, that there is an impermissible reliance on this exemption."

The NRAR declined to be interviewed but confirmed it was investigating.

In a letter to the EDO, it said it would examine the rules around water use and exemptions before it would commit to look at other issues specifically related to Maules Creek Mine.