The Australian Government has released a series of reports on the impacts of 22 proposed coal mine projects on water resources in the Hunter sub-region on the country’s south-east coast.

The two most significant reports, titled ‘Assessing impacts of coal resource development on water resources in the Hunter subregion’ and ‘Impact and risk analysis for the Hunter subregion’, conclude it is ‘very likely’ that there will be a significant drawdown of the region’s groundwater resources and a reduction in mean annual flow in the Hunter Regulated River. The 22 proposed projects include the expansion of existing mines and the construction of entirely new mines in the region.

“Potentially impacted ecosystems in the zone include 102km2 of groundwater-dependent ecosystems (predominantly rainforests, forested wetlands and wet and dry sclerophyll forests), and 634km of perennial and 518km of intermittent streams,” reads the former report.

An area measuring 2,441km2 is expected to experience 0.2m of drawdown if mining expansion takes place in the region; an area measuring 1,879km2 overlaps with the larger area and could ‘potentially experience cumulative groundwater impacts’. This would be triggered by an increase in CSG mining in the area, which requires groundwater extraction to complete its operation

Surface water is likely to be similarly affected. The reports identify Wyong River, Loders Creek, Saddlers Creek and Wollar Creek as bodies of water whose flow could be significantly disrupted by further coal mining operations. The reports predict that these areas will experience at least 20 additional days per year of low-flow days, periods where the water level in streams is reduced as if experiencing prolonged dry weather. Similarly, there will be ten fewer high-flow days per year and decreases in mean annual flow volume of 20%-50%.

“The combination of runoff interception and changes in baseflow caused by groundwater drawdown contributed to increases in low-flow days,” reads the first report.

The report concludes that 21% of streams and rivers in the Hunter sub-region could be affected by the expansion of coal mining, and names forested wetlands, perennial streams and intermittent streams as three of the ecosystems that could be most significantly affected.