AN innovative trial at Pindari Dam north of Inverell is delivering exciting results for native fish habitat and inland river biodiversity health in New South Wales, by addressing one of the major factors in environmental decline – cold water pollution.

Launched earlier this year, the trial of the $26.2 million bubble plume project is already making a positive difference by creating warmer temperatures throughout the Severn River’s Pindari Dam storage.

The trial is led by WaterNSW, in collaboration with the NSW Department of Primary Industries and Regional Development and funded by the Federal Government.

The newly installed bubble plume system, the largest in Australia, mixes the water in the dam to minimise cold water pollution during the summer months, resulting in more consistent temperatures within the dam and downstream.

As a result, water temperatures at the bottom of the dam rose over 6⁰C in one month.

Cold water pollution occurs when frigid water from the depths of major dam storages is released into the river downstream, reducing the temperature of the water to well below the natural levels to which the environment is adapted.

This change in temperature has a negative impact on the natural habitat, affecting the entire riverine ecosystem and inhibiting native fish from breeding and thriving.

While the trial will be paused over the cooler months, preliminary results have confirmed the ability of the bubble plume to mix the entire dam. The trial will recommence in spring 2026.

The project is part of the North Basin Toolkit Program, a group of measures delivered in collaboration with the NSW and Queensland Governments that aim to complement environmental outcomes and help deliver additional water for the environment.

The project has been delivered with the support of construction partner Eyre Constructions.

NSW Minister for Agriculture, Tara Moriarty said when there are healthy rivers and native fish populations, regional communities benefit in environmental, social and economic ways.

“These early results of this project are positive for native fish. Half of all expected native fish species are missing below New South Wales’ largest dams, with cold water pollution implicated as one of the key impacts.

“This project aims to re-establish more natural water temperatures below dams for native fish breeding and growth. The project also ensures that water temperatures from environmental flow releases enhance the health of the river downstream.”

NSW Minister for Water, Rose Jackson said fixing cold-water pollution doesn’t just help the environment, it delivers real benefits for farmers, towns and everyone who depends on the waterways.

“This is an innovative trial run by WaterNSW, in partnership with Fisheries and our federal partners, which is already showing promising signs of restoring healthier temperatures for our rivers and native fish,” she said.

“As the trial continues, we look forward to building on the momentum already achieved, strengthening our river ecosystems and ensuring our native fish species have the conditions they need to thrive.”

WaterNSW Executive general manager of Built Infrastructure, Jerome Douziech said cold water pollution is a well-recognised environmental issue associated with dam operations, especially the large supply dams that are typical to regional New South Wales.

“While the trial is yet to run its course, the fact that initial results are encouraging in a dam as deep as Pindari, means WaterNSW, along with our environmental partner agencies, and government more broadly are watching with great interest whether this method could be effective at other locations across the state,” he said.