Undermined supplies studied
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Experts say mining-induced damage to peatlands threatens Sydney’s water supply.
Recent research has shed light on the serious and potentially irreversible impacts of longwall mining on peatland ecosystems in the Sydney drinking water catchment area.
A new study, which focuses on an upland peat swamp undermined by mining activities in 2020, highlights the significant disruption to peatland hydrology, including substantial water loss and diminished surface flows.
The findings raise concerns about the long-term ecological and water security implications for the region.
Peatlands, though covering only 3 per cent of the Earth's surface, are the planet’s largest terrestrial carbon store and play a crucial role in freshwater storage.
In Australia, peatlands, particularly those in the Sydney catchment area, are essential for maintaining the quality and supply of drinking water.
However, the study’s findings indicate that the longwall mining method, which involves the removal of large panels of coal, has caused significant damage to these sensitive ecosystems.
The research was conducted on an upland peat swamp in the catchment headwaters, an area crucial for Sydney’s water supply. Using a conceptual hydrology model, the study measured the water balance before and after the swamp was undermined in 2020.
The results were stark: post-mining, there was a marked increase in deep seepage rates and a drastic reduction in surface water discharge.
The study noted that before mining, the swamp had a median flow rate of 15.2 cubic metres per day, which dropped to zero following the mining activity.
The study also found that the groundwater table, which supports the swamp's ecosystem, began to recede rapidly after rainfall events.
In some cases, wells recorded the complete absence of water within just eight days of rainfall, leading to the conclusion that the swamp’s water storage capacity had been severely compromised.
This rapid drainage not only threatens the peatland’s biodiversity but also reduces the volume of water flowing downstream to Sydney’s reservoirs.
The study warns that the damage caused by longwall mining to peatlands may be irreversible.
“Natural processes of remediation, such as infilling of subsidence fractures with sediments, are unlikely to substantially reduce vertical hydraulic conductivity,” the UNSW researchers said.
This suggests that once a peatland has been undermined, its ability to retain water and support its ecosystem could be permanently impaired.
Given these findings, the study advocates for a more robust approach to water management in regions where mining activities overlap with sensitive peatland environments.
It suggests that water management policies should be updated to include guidelines specifically aimed at protecting these areas from further water loss due to mining.
The researchers also highlighted the need for more comprehensive environmental regulations that account for the cumulative impacts of mining on peatlands.