IM’s July issue (just out) considers water managment. The World Business Coucil for Sustainable Development has just made available a case study on some of Rio Tinto’s work. Due to its tropical and monsoonal climate, northern Australia often experiences an excess of water that occurs less frequently in southern Australia. Rio Tinto’s Weipa bauxite mining operations in the region have multiple sources of water, each of which has its own associated costs and additional values.

The four main sources are:

1. Decant water (recycled or reused water) from the tailings dam
2. Site rainfall run-off captured in “slots” (like small wells) and other small storage sites across the mining lease
3. Shallow aquifers underlying the area
4. The deeper aquifers of the Great Artesian Basin.

Availability of the different sources can vary during the year, particularly the first two. Rio Tinto identified the level of sensitivity of the shallow aquifers and the Great Artesian Basin during normal environmental risk management processes. This has been reinforced by engagement with key stakeholders, including the Great Artesian Basin Coordinating Committee and nongovernmental organizations. The latter have focused on the connectivity that can occur between the shallow aquifers and local rivers.

These processes have aided the establishment of a formal hierarchy of sources, directing the operation to source first from tailings dams, then “slots”, then the shallow aquifers, and finally the Great Artesian Basin aquifers.

In general, the costs associated with sourcing from tailings dams and slots are less than those arising from operating borefields fed by underground aquifers. However, due to the large area of the mining lease, there are situations where it could be both cheaper and more convenient to source from one of the latter.

The establishment of the sourcing hierarchy effectively places an implicit value on the natural sources of water. In the case of the Great Artesian basin, the focus is on the long-term sustainability of the resource, as it has the slowest rate of recharge. The shallow aquifers recharge very quickly due to the climate; their shallow depth, though, can be linked more closely to the river ecosystems.