Has mining affected water supply in fire stricken New South Wales?

Scarlett Evans 10 December 2019 (Last Updated December 11th, 2019 12:05)

With rapidly declining dam levels and bushfires raging through the state of New South Wales (NSW), the issue of water scarcity has never been more topical. Now, an independent report has warned of the damage posed to Sydney’s drinking water by local mining operations, causing the government to put upcoming coal projects on hold. Here, we look at exactly what the impact of mining projects on water supplies is, and what’s next for Sydney’s mining industry.

Has mining affected water supply in fire stricken New South Wales?
Metal-contaminated water downstream of a section of Creek (Eastern Tributary, Woronora NSW) that has been damaged by stream channel fracturing caused by mine subsidence. Image courtesy of Dr Ian Wright

Fears over water supply in Sydney, and indeed the whole state of NSW, have been growing in recent years. Dam levels are dropping at the fastest rate since 1940 and figures from WaterNSW show that the warning storage level was reached in January this year, with Sydney’s desalination plant stepping in to provide drinking water to residents. As of November, dam levels were found to be at less than half of capacity (47%), and some mines in the state have warned they may soon run out of water entirely.

The report was authored by a panel set up in 2018, tasked with investigating water losses in Sydney’s drinking water catchment due to mining operations. Submitted to the Department of Planning and Environment, it made 50 recommendations on how projects in the region could be adapted to save water, and made the case for increasing research into this still relatively untapped area. With environmentalists and industry members alike supporting the measure, Sydney’s mining industry awaits news of the next step.

Mining’s impact on water supplies

The report found mining could cause water losses of up to as much as eight million litres per day – equivalent to 2,920 million litres per year. Water use at the two operational mines in the region (Peabody’s Metropolitan and South32’s Dendrobium) is also predicted to increase as the excavation areas extend. The primary cause is the use of longwall mining, a method that can lead to subsidence – or the collapsing of land – which blocks the flow of water bodies, proving problematic even once the sites have been discontinued.

“A lot of water continues to flow into the mines that have been shut down, because there are voids left where coal has been removed,” says Nic Clyde, a spokesman for environmental organisation Lock The Gate. “That water flushes out heavy metals, salts – all the things you don’t want in your fresh water supplies.”

“In some cases there’s no real way of stopping it,” he adds. “Once you’ve mined the coal, you’ve got a problem – and I’m not sure if anyone really knows how long it will last. There’s certainly projections of Dendrobium having impacts into the middle of next century.”

Other water losses were found to come from surface water diversions into the mines, leakage from reservoirs and loss of baseflow due to groundwater depressurisation. With the long-term impacts of operations still relatively uncertain, the study’s authors advocated for increased research into the matter, defining current projects as having an ‘incomplete’ design knowledge base, with ‘high potential consequences’ if mine design does not suit the circumstance.

“Research into this area can and should be done,” says Dr Ian Wright, a senior lecturer in Environmental Science at Western Sydney University and previous catchment officer in Sydney Water’s drinking water regions. “The fact that it isn’t is not a blight on the mining industry, but a blight on the government. The regulators here have allowed the situation to develop, so you can hardly blame the miners for causing impacts when the regulators have allowed them to.”

Proposed solutions in the report include ‘purchasing’ water lost in the catchment, with the financial offsets funnelled towards replacement water sources. However, the panel said provisions are needed in the instance that the water table cannot be re-established, and others have said this does not solve long-term damages to the region.

Is enough being done?

The panel’s report is only the latest in a series of warnings that the current situation in Sydney is unsustainable. In the same panel’s first report, released in November 2018, it said it was ‘plausible’ that Dendrobium was diverting as much as three million litres of water per day.

In November 2019, the NSW Government announced a pause on new approvals for coal mining under water catchment following the publication of the report, a pause which is expected to continue well into 2020.

While the government’s pause is welcome, industry members remain uncertain as to what the result will be.

“I applaud the government pausing for breath,” says Wright. “But I don’t think it’s going to be much more than that. I don’t think this is going to stop longwall mining – it’s the most efficient method for removing coal. The industry understands there are surface impacts, but I think it’s going to be a question of scaling back and staying away from large waterways.”

Wright points to the Berrima Colliery as evidence of a rehabilitation scheme gone right. In this instance, water pollution from the mine became far worse following its closure, but, in a rare move, the miner (Boral) returned to the site to mitigate damages.

“It’s the first underground mine that caused pollution where the miner has gone back in,” he says. “They installed a treatment system, and they sealed the mine up to contain the pollution. I’m extremely proud of what they did. A lot of mines are shutting, and operations often leave a disturbed a polluted heritage. But this shows the work that can be done.”

While Boral’s initiative offers a hopeful example of rehabilitation’s potential, for some industry members mining’s effects are already too dear.

“We’ve got a climate that is getting hotter and drier, a growing population, and we’re in the grip of one of the worst droughts in living memory. The question is – how much is too much?” Clyde asks. “The mining industry might like to play down the damage to the catchment, but there are some very big questions and expensive problems that need to be solved.”

‘Catastrophic’ fire warnings mean nothing must be left to chance 

Climate change is indeed another factor for mining companies to consider. A 2018 study from the University of New South Wales showcased a new paradox being faced – despite more intense rain, globally we are seeing water scarcity due to parched soil soaking up most of the rainfall.

“What we are noticing is that with each degree rise in temperature, there is an expected increase in rainfall extremes,” says Professor Ashish Sharma, who led the study. “However, with the same degree rise in temperature, there is a decrease in peak flows, which can only be a result of the rain falling on a drier catchment.”

Add to this the current spread of bushfires throughout NSW, with the state’s Rural Fire Service issuing its first-ever “catastrophic” fire warning for the Greater Sydney and Greater Hunter areas. While firefighting water supplies differ from drinking water, the net result is an atmosphere of fear, and a realisation that any water unnecessarily lost is, indeed, too much.

“This is not the first time we are facing water insecurity. We have faced this before and handled it successfully,” says Sharma. “We just need to have the commitment to undertake something similar once again. And we can’t wait for too long. Dryness will only get worse as temperatures rise to 3.5°Cby the year 2100.”