The amazing recovery of a heavily polluted river in the heart of the Blue Mountains World Heritage area

For more than 40 years, an underground coal mine has dumped poorly treated sewage directly into the Wollangambe River, which runs through the heart of the Blue Mountains World Heritage area.

Much of this spectacular wilderness river was chronically polluted, with dangerously high levels of zinc and nickel. Few animals were able to survive there.

My colleagues and I have been calling for stricter regulations to clean up the sewage stream since 2014, after we first sampled the river for our research. Finally, with the rallying of the Blue Mountains community behind us, the New South Wales Environmental Protection Agency (EPA) has imposed stricter regulations in 2020.

Our latest research paper documents the recovery of the Wollangambe River since. We have already seen a massive improvement in water quality, with wildlife returning in impressive numbers to once polluted sites.

In fact, the long fight to restore this globally significant river is the focus of a new documentary, Mining the Blue Mountains, released this week (and online in the coming days).

Trailer for Blue Mountains Mining.

But while the recovery has been promising so far, it remains incomplete. Much more action is needed to restore the river to its former state of health.

How bad was the river?

When the federal government proposed the Blue Mountains for inclusion on the World Heritage List in 1998, it asserted that “some coal mining takes place nearby, but does not affect the water catchments that run off In the region”.

Our research has shown that this is not true, and the pollution of this river has caused international concern. In 2020, the International Union for Conservation of Nature – an official adviser to UNESCO – identified the coal mine as a major threat to the conservation values ​​of the Blue Mountains World Heritage area.



Read more: The Blue Mountains World Heritage Site has been decommissioned, but it’s not too late to save it


So how bad was the pollution? Our previous survey, conducted nine years ago, focused on both water quality and river invertebrates, primarily aquatic insects.

Wastewater from the Clarence Colliery underground coal mine discharged into the Wollangambe River approximately 1.5 kilometers upstream from the boundaries of the World Heritage area. The nature of the pollution was complex, but the most serious concern was the increased levels of nickel and zinc in the river.

Clarence Colliery is an active underground coal mine located near and above the boundary of the Blue Mountains World Heritage Area.
James Patrick Photography, Author provided

These metals were unusually enriched for coal wastewater, both at concentrations more than 10 times known safe levels. Pollution remained dangerous for more than 20 km downstream, deep within the World Heritage area.

Compared to upstream and unaffected reference streams, we found that invertebrate abundance in the Wollangambe fell by 90%, with invertebrate family diversity being 65% lower below the outlet of the mining waste.

There was also an accumulation of contaminants in the surrounding food chain. For example, one of our studies detected accumulated metals in plants growing on the river bank. Another found an accumulation in water beetle tissue below the mine outlet.

Water specialist Callum Fleming in the headwaters of the Wollangambe River, upstream from the mine outfall.
Ian Wright, Author provided

Life returns to the river

In 2014, we not only shared the results of our published research with the NSW EPA, but also with the Blue Mountains community. This sparked a letter-writing campaign from the Blue Mountains Conservation Society urging the EPA to take action.



Read more: How our research is helping clean up coal mining pollution in a World Heritage-listed river


After five long years, the EPA finally issued strict regulations requiring Clarence Colliery to significantly reduce the release of pollutants, particularly zinc and nickel, in the mine’s waste discharge.

And it worked ! We took samples 22 km down the river and were very surprised at the speed and extent of ecological recovery. Not only has the water quality improved, but the animals are also coming back.

The Wollangambe River 22 km downstream from the mine waste outlet. This photo was taken in December 2020, when river pollution was decreasing and invertebrate life was beginning to thrive.
Ian Wright, Author provided

The improved treatment has resulted in a very significant reduction in zinc and nickel concentrations in mine wastewater, which continues to be closely monitored and made public by the mine.

The groups of invertebrates most sensitive to pollution – mayflies, stone flies and caddisflies – saw a large increase (256%) in abundance from when we conducted our previous research in 2012 and 2013 .

This could have positive implications for surrounding plants and animals, as river invertebrates are a major food source for waterfowl, lizards, fish and platypus.

Western Sydney University water science researchers Callum Fleming (l) and Ian Wright (r) cool their feet in the Wollangambe River.
James Patrick Photography, Author provided

However, the road to recovery is long. River sediments remain contaminated from the accumulation of four decades of zinc and nickel enrichment, up to 2 km downstream of the mine outlet.

To help speed the recovery of the river, contaminated sediment is to be removed from the river below the mine outfall, as a 12-month clean-up operation carried out after a major mine spill in 2015.

Pollution does not often stop with mines

Unfortunately, there are closed mines in the Blue Mountains that continue to release damaging pollution, such as Canyon Colliery and several in the Sunny Corner Gold Mine area, as the documentary explores.

Canyon Colliery closed in 1997 and contaminated groundwater continues to flow from its drainage wells into the Grose River, part of the Blue Mountains World Heritage Area.

Author Ian Wright looks at the polluted drainage from the Canyon Mine flowing towards the Grose River.
James Patrick Photography, Author provided

Likewise, most of the mines in Sunny Corner closed over a century ago, yet severe pollution still seeps from the mines into the waterways.

The pollution here is in extreme concentrations and includes arsenic, copper, lead and zinc. It is dangerous for life in the waterways, the surrounding soils and contact with this pollution is dangerous for human health.

Sunny Corner is a silver and gold mining area that closed a century ago but still releases highly contaminated mine drainage.
James Patrick Photography, Author provided

What can we learn from this?

Rehabilitating these closed mines is expensive and often with limited success. But the Wollangambe River case study is an encouraging sign that cleaning up is possible for even the most polluted environments.

Strong independent scientific research and community involvement are essential to these efforts. The community is the eyes and ears of the environment and has an important role to play in holding industry and government regulators to account.

Environmental regulators, such as the NSW EPA, have enormous power to tackle pollution and trigger positive change. It’s important that researchers and the community engage with them – and it helps to be patient because action can take years to materialize.

Finally, we commend Centennial Coal, owners of Clarence Coal Mine, for making huge improvements to their operation and complying with tough new environmental regulations.



Read more: Cutting the “green strip” may be good political policy, but it is bad policy. Here are 5 examples of regulation failure


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