The Indian mining giant wants to build a pipeline to “harvest” 12.5 billion litres of water from the Suttor River to clean coal and suppress dust at the mine site.

The Australian Conservation Foundation says the Morrison Government made an error of law when it initially assessed the yet to be approved North Galilee Water Scheme.

It should have applied the “water trigger” law, which assesses the impacts of coal seam gas and large coal mining developments on aquifers and rivers.

The government’s view was the trigger wasn’t applicable because the scheme doesn’t involve the physical extraction of coal, it supplies water.

There’s also a different company proposing it – Adani Infrastructure – to that building the coal mine, which is Adani Mining.

The projects will be financed separately and should be assessed separately, it said.

But ACF’s lawyer Neil Williams SC says both are clearly subsidiaries of the Adani Group and the NGWS is ultimately part of the mining process.

“It calls into question how wide the definitions of coal mining activity and the action involving large coal mining development are,” he told the Federal Court in Sydney on Monday.

Williams said Adani registered Adani Infrastructure in 2015 after Adani Mining’s initial water plans, which included the NGWS, were scrapped in 2014.

“By using a different proponent and not including the coal mining for which the water will be devoted, Adani claims that for which originally formed an integral part of its coal mine proposal no longer involves coal mining,” he said.

“We say that having regard to the (law), that can’t be right.”

But Adani lawyer Stephen Lloyd SC said the scheme is just “a very large plumbing project” involving pumps and a pipeline.

“It’s not a coal mining activity,” he said.

Lloyd said the mine has already been approved and the NGWS was simply a piece of infrastructure to provide an alternative source of water as a backup.

“One has to ask if it falls within the definition of coal mining activity,” he said.

The hearing continues.