Findings from the Namoi catchment water study strengthen the case for BHP Billiton and Chinese group Shenhua to progress their coal mining projects in the nearby Liverpool Plains, which have been opposed by rural groups claiming mining will damage the region’s aquifers.
The results indicate that even under hypothetical mining scenarios based on coal production levels significantly higher than currently approved or proposed, the potential impacts on the high value alluvial aquifers are relatively small in the context of natural variation and the impacts of existing groundwater extraction, according to NSW Minerals Council chief executive Stephen Galilee.
“Despite making assumptions that overestimate the likely impacts of coal mining on water resources in the region, information we have seen as part of the study demonstrates that the cumulative impacts of mining are likely to be within the historical impacts of agricultural water use across the region,” he said.
The Namoi water study was commissioned by the NSW government to investigate the potential cumulative impacts on water resources in the Namoi catchment from mining and coal seam gas activities in response to concern from some parts of the community.
The study was funded by the coal industry, CSG industry and the Australian government.
It was undertaken by independent consultant Schlumberger Water Services which was selected by a multi-stakeholder Ministerial Oversight Committee and undertook the study in accordance with terms of reference developed by a multi-stakeholder panel.
The NSW government renewed the exploration licences for BHP Billiton’s Caroona coal longwall project and China Shenhua Energy’s giant Watermark coal project in the Liverpool Plains in September last year but imposed various environmental conditions.
Under the study’s hypothetical scenario 3 which models growth in coal production well beyond what is planned in the region, the study’s authors state that “both the lower and upper Namoi alluvium will experience a relatively low impact when compared to existing anthropogenic water use impacts”.
Scenario 3 models a coal production rate of 60 million tonnes per annum by 2014 that continues for 85 years, from a total of 24 open cut and seven underground mines.
In comparison, there are only 12 mines approved or planned in the region, while current extraction rates are less than 10Mtpa and are expected to reach 30-45Mtpa over the next 10-15 years.
Mining currently uses well under 0.1% of land within the region.
Under Scenario 3, predicted maximum average drawdown in the alluvial aquifers from 2010-2100 range from 0.1m to 1.6m.
It compares to historical average drawdown over the past 30 years of up to 7.9m.
Despite the encouraging results from the study, Galilee said coal mine proponents would still need to undertake detailed assessments of their potential impacts on water resources when putting forward proposals to gain a full understanding of localised impacts, which was beyond the scope of a regional model.
If approved, mines would need to obtain water licences for any predicted impacts on water resources, in accordance with relevant water sharing plans.
“The report provides a good overview of the geology and groundwater resources of the Namoi catchment, including particular areas where risks need to be carefully managed and an indication of the potential cumulative impacts of hypothetical future coal mining and coal seam gas projects in the region,” Galilee said.
“However, the independent expert from Schlumberger, who undertook the study, has made it clear that this regional model does not replace the need for detailed, case by case assessments of each mining project to help decide whether or not they should proceed.
“The industry is committed to undertaking these detailed studies.”
The study was the first of its kind in NSW and represented a significant advance in the understanding of the region’s water resources, Galilee said.
“Over time, as there is greater certainty about potential development and more data becomes available, fewer assumptions will be required and improved predictions will result,” he said.
“The collection of this data is an integral part of the assessment process for mining proposals.
“The region’s coal industry is proud to have funded and provided important data for what will undoubtedly be a valuable tool for water resource planning, not only for the coal industry but for all water users in the region.”
