Mining company Adani has bypassed the need for a full environmental impact assessment, against governmental advice.

The Federal Environment Department has ruled against the advice of its own water experts to allow Adani's North Galilee Water Scheme, in Central Queensland, to move ahead without a full environmental assessment.

Activist group Lock the Gate Alliance has obtained documents that show the Department of Agriculture and Water Resources wrote to the Environment Department suggesting the project could activate the ‘water trigger’ – which is intended to ensure gas and coal mining projects that could significantly impact water resources undergo full environmental assessments.

The Department of Environment ruled Adani's water project - which involves the extraction of up to 12.5 billion litres of water a year from a Queensland river to support the Carmichael coal mine - did meet the terms of the trigger.

The department decided that the water project is separate to the mine.

But that conclusion runs against the view of experts in the Department of Agriculture and Water Resources.

A submission to the Environment Department from the Department of Agriculture and Water Resources read:

“The department considers the proposed action could have significant impact(s) on a water resource, in relation to coal seam gas development, protected under the EPBC Act.”

The Queensland Environmental Defenders Office wants the Environment Department to explain how it came to its decision.

A statement from both the Department of Environment and the Environment Minister says the advice of other departments was considered.

“The Adani project has been subject to more than 150 state and federal government conditions, so we are confident any potential impacts are being adequately assessed,” the statement read.