The Australian Government has assessed how 22 potential new coal mines or expansions of existing coal mines could affect groundwater and surface water resources in the Hunter sub-region.
The Australian Government’s Bioregional Assessment Programme, which was published earlier this week, indicated that an area of 2441 square kilometres could experience groundwater drawdown due to potential new mines or mine expansions. The Hunter sub-region spans an area of 17,045 square kilometres and a population of more than 800,000 and is known for its coal mining, power generation, equine and viticulture industries. The area spans 68 mining operations comprising of 41 baseline mines and 17 additional coal resource developments. Several new or expanded mine proposals like United Wambo were not included in the assessment.
The report, which found its information through rational scale hydrological modelling, found the existing 40-plus open-cut and underground coal mines had affected an area of 4307 square kilometres and that the 22 new projects would expand that impact.
The Hunter sub-region forms a part of the Northern Sydney Basin bioregion and includes two Ramsar‑listed wetlands in addition to forming a part of the Greater Blue Mountains World Heritage Area. Large changes in flow regime were found possible in the areas of Wyong River, Loders Creek, Saddlers Creek, Wollar Creek and several ephemeral creeks. This area features roughly 1228 kilometres of streams and 102 square kilometres of groundwater-dependent ecosystems: including rainforests, forested wetlands, and wet and dry sclerophyll forests, which could potentially be affected by fluctuations in groundwater or surface water. This area currently sees an annual rainfall of 793 millimetres.
The assessment found that Drawdown of greater than 0.2m is very likely (greater than 95% chance) to occur at distances of 5km from mine sites. The effects on groundwater were also found to diminish with distance from the mines.
Modelled changes in hydrology could affect the management of the Hunter Regulated River or the reliability of water supply in some unregulated streams, more information is also being developed on this at the current moment.
Water losses are expected in the Singleton, Muswellbrook and Jerry’s water sources according to the assessment. In the Singleton source, there’s a 50% chance of 4.5GL loss of flow, which is 24% of the annual flow of that water source.
“This represents a risk to agriculture in the region, and is even more concerning during a drought like the one we are experiencing at present when farmers are under pressure already and reliant on groundwater,” voiced Lock the Gate Alliance spokesperson, Georgina Woods.
The Australian Government has stated in full disclosure that more information and future monitoring is needed to determine further risk in these areas. An example which was stated in the Bioregional Assessment Programme was using local information from the Wallarah 2 environmental impact statement, which greatly reduced modelled changes in the flow regime of the Wyong River. Scientists used the best available data to describe coal and coal seam gas resources and to assess potential changes to surface water and groundwater due to proposed new coal resource developments.
More information on the assessment can be found at http://www.bioregionalassessments.gov.au/assessments/hunter-subregion