The efficiency of water extraction and the containment of wastewater are key aspects of operational performance. Water is used in most aspects of operations, including exploration, mining and processing.
Table C: Water input, recycling and discharge megalitres (ML) by quality
|Water to TSF3||3,922||0||3,922|
1 High quality: water having less than 1,500 milligrams per litre total dissolved solids, pH between five and nine, and individual dissolved constituents at concentrations suitable for agricultural/livestock and irrigation use (based on local/regional/national guidelines).
2 Low quality: water with total dissolved solids greater than 1,500 milligrams per litre or with dissolved constituents (metals, anions etc) greater than local guidelines for agricultural/livestock or irrigation use, or with pH less than five or pH greater than nine.
3 Tailings Storage Facility.
OZ Minerals’ total water use during the reporting period was 5,253 megalitres, with 5,243 of this total being consumed at Prominent Hill and sourced entirely from groundwater bores. Over this period, 3,922 megalitres of water was returned to the tailings dam at Prominent Hill. Our exploration operation in Cambodia sourced water from municipal water supply and surface water.
Situated in a location with a relatively low average annual rainfall of approximately 160 millimetres, the Prominent Hill site is dependent on the supply of groundwater to sustain its operation. Prominent Hill draws its water from the Boorthanna Formation geological unit of the Arckaringa Basin. This groundwater system is discrete from the Great Artesian Basin aquifer system that feeds the Great Artesian Basin springs, and no influence on these springs is expected. The operation well field is located approximately 30 to 40 kilometres south-east of the mine and is operated under a miscellaneous purpose licence.
At our Prominent Hill site, a potential issue is arising regarding the impact of the water drawdown on two bores of a pastoralist in the Prominent Hill area. Additional monitoring and modelling is being put in place to determine the likely impact on the bores as a result of the operation of the Prominent Hill borefield. This will dictate any mitigation plans that will need to be put in place in line with the compensation agreements with local pastoralists.
The CSIRO has commenced water modelling and analysis at Prominent Hill. The CSIRO is using Water Pinch Analysis, which is a technique used to facilitate reduced water consumption.