Coal mining in Sydney's catchment is having a "cumulative and possibly accelerated" impact on water flows but its full effect is unknown because of a lack of monitoring.
These are among the findings of the 2016 Audit of the Sydney Water Drinking Catchment, a study required by law every three years, that the Berejiklian government quietly tabled in parliament this month. Just a single copy of the report was available to borrow.
The audit, which covers the 16,000-square-kilometre catchment that stretches from Lithgow in the Blue Mountains to near Cooma and stores as much as 2.6 million megalitres of water, found "reduced water availability" compared with the 2013 report.
It found mixed trends, with parts of the catchment improving but others worsening. Lake Burragorang - Sydney's main reservoir sitting behind Warragamba Dam - was among areas with the poorest results for surface flows.
Water extraction by mining and other uses continue to increase, while wetlands appear to have deteriorated. There had also been "a significant increase" in areas affected by bushfire, the audit said.
"The audit found an emerging issue of unquantified loss of surface flows associated with the cumulative impacts of underground coal mining activities," it said.
Peter Turner, mining projects science officer for the National Parks Association said the audit "paints a picture of a catchment under pressure and continuing to be damaged by coal mining".
A spokesman for Energy Minister Don Harwin said the audit showed the city's drinking water "has the highest possible quality rating in the world" and it was a top priority to maintain the standard."[T]he government is looking closely at the independent audit and will ensure that whatever actions are required to protect our catchment are taken," he said.
The audit's release comes at an awkward time for the government. The Supreme Court this month ruled invalid the approval for the extension of the Springvale coal mine because the mine pumps untreated waste into the Coxs River that flows into Lake Burragorang, accounting for about 80 per cent of Sydney's water.
Springvale, though, is the sole supplier to the Mt Piper power station, which generates about one-sixth of NSW electricity. The government may need special legislation to nullify the Supreme Court's decision and concerns about mining in the catchment raised by the audit may complicate its case.
Stuart Khan, an associate Professor in the School of Civil & Environmental Engineering at the University of NSW, said the trends revealed for Lake Burragorang were "very concerning".
Electrical conductivity- which gauges how salty the water is - had been worsening in the lake for the past two decades, as had other water-quality parameters such as nitrogen and dissolved oxygen.
Rising nitrogen and falling dissolved oxygen levels would traditionally have been associated with sewage issues but, as the audit notes, plant upgrades had significantly reduced the burden from this source.
"Worsening salinity at a time when the lake is full points to long-term catchment decline," Professor Khan said. "This means that the salt and nitrogen contamination reflects increasing emissions from other sources such as mining and agriculture."
Sydney's catchment suffered a major cyanobacterial bloom in 2007. "By allowing nitrogen concentrations to gradually increase, we are setting ourselves up for the risk of more large-scale bloom events in the future," he said, adding more science "is urgently required" to understand the sources and develop effective controls.
As with previous audits, this report highlighted "inadequate" data and monitoring. Key datasets, such as those tracking native vegetation, had not been updated since 2013, it noted.
"The audit records the potential for mining to cause significant and serious groundwater loss" in the special areas that are intended to protect the core of the catchments for the reservoirs that supply Greater Sydney and the Illawarra, Dr Turner said.
"It does not, however, record that the available evidence strongly indicates that this is already happening." (See detailed NPA comments on the audit here.)
That omission is "puzzling" since company reports already indicate some 29 to 40 million litres of water a day are entering mines in and around the Metropolitan and Woronora Special Areas, Dr Turner said.
"This corresponds to 10,585 to 14,600 million litres of water a year," Dr Turner said. "This is a disturbingly large volume and is as much or more than some of the licence-restricted water extractions permitted in sub-catchments outside the special areas."
The water inflows to the underground mines are caused by subsidence after the fossil fuel is extracted, leading to fissures that can divert water from aquifers or from surface rivers and swamplands.
"Mine inflows can't be turned off with a tap," Dr Turner said. "They continue until there's no more water or until the mine fills and leaks its contaminated water."
Even research, it seems, falls through the cracks.
Research recommended in the 2010 audit into the connectivity of surface and ground water that had been identified as underway three years later couldn't be found.
"[N]o published results could be located either in the public domain or through communications with key personnel within DPI Water and WaterNSW," the 2016 report said.
Surface water loss can also dry out endangered swampland, adding to the bushfire risks, the audit said.
"[S]uch losses could be significant in dry and drought conditions," it said. "The loss of surface water can also impact on bushfire severity, and thus the condition of upland swamps and their flora and
Coal mining in the Schedule 1 Special Areas itself "makes nonsense of the legislated intent" of the protected areas, Dr Turner said, noting that water extraction is not permitted in the nationals parks that border the Metropolitan and Woronora regions.
"The National Parks are protected from water loss, but not the Special Areas, which are in effect Sydney's most important public health asset, he said. Those areas are also high
conservation regions and "contain some of the few remaining areas of pristine bush in NSW".
Greens NSW environment spokeswoman Mehreen Faruqi said it was "simply irresponsible" to continue to allow longwall coal mining in Sydney's catchment.
"Streams nearby these mines have gone from gaining groundwater to now losing it, which is having significant impacts on their flows and environmental outcomes for wetlands," Dr Faruqi said.
"It's pretty disappointing that this audit was tabled with no explanation or notification to stakeholders. Surely issues such as drinking water which impacts everyone deserve more transparency," she said
The next focus on water may come if the government attempts to pass legislation aimed at nullifying the Supreme Court's decision on Springvale mine.
"The [State Environmental Planning Policy] was put in place for public health reasons, to ensure that the water supplied to the communities of Sydney and surrounds is safe," Ms Higginson said.
"It would be hard to envisage a basis upon which a government would reverse standards and policies that were put in place for this reason."