Changes to the way the NT Government allocates water to industries, particularly for onshore gas projects in the Beetaloo Basin, could cause water flows of the Roper River to move in the opposite direction and stop completely, according to a confidential government memorandum released under freedom of information laws to the Environment Centre NT.

The memo was described by ECNT co-director Kirsty Howey as “shocking” and pointing to potentially “catastrophic impacts on iconic territory waterways”, including the Roper River and the Mataranka Hot Springs.

Nevertheless, the government moved to grant a water licence in the area using arid zone rules with no mention of the internal document that had raised issues.

The ECNT said the memo, written by the then-Director of Water Planning and Engagement shows the government knowingly acted against their own scientific advice that the river could be decimated.

“It’s crucial that there is transparency, accountability and a precautionary approach taken with these plans,” Ms Howey said. “This approach must accord with the science and not permit water mining, which is what the arid zone facilitates.”

The memo warned the Territory government to be vigilant in drafting water allocation plans for the Beetaloo Basin in particular, as the government is expected to release proposed water allocation plans that will guide water management for new gas projects in the Beetaloo Basin.

Water allocation is managed through water licenses and allocation plans in the Territory. If there is no allocation plan in place for a region, it would fall under two zones, the top end zone and the arid zone.

The NT Government has been using the arid zone rules in the northern part of the Beetaloo Basin to guide its decisions, which allows it to allocate 80 per cent of water stored in aquifers to industry. However, the memo stated that allowing 80 per cent of the Mataranka Tindall Limestone Aquifer to be used could “cause water to flow in the opposite direction towards Larrimah” and impact “environmental and cultural values” of the Roper River.

If the river were to flow in the opposite direction, the discharge needed to maintain the Dry season flow could see it dry up completely, experts warned.

“The last few years have been some of the driest on record and may indicate the start of a drier climate period,” the document, written by Tim Bond, stated. “A precautionary approach would warrant allocating water on the basis of long term median values rather than the last 30 years.”

The Environmental Defenders Office said that the Territory Government’s water allocation plans (WAP) are highly irregular and cause for considerable concern. As an example, the EDO cited the approval of the Singleton Station license “the ‘guideline document’ that the Water Controller relied upon to avoid provisions of the WAP had been drafted by the Water Controller themselves in their separate capacity as CEO of the Department of Environment, Parks and Water Security.”

A spokesperson for the Environment, Parks and Water Security Department said the advice in the memo was only the “view of one staff member” and not agreed with by other officials. The government said it had not changed the rules that govern water allocation, but had “better defined the delineation of what is considered either an arid or top end aquifer or waterway based on characteristics, geography and rainfall and recharge”.

The department said forthcoming water allocation plans would take into account environmental and water flow protections.