The El Niño weather event and its effects on water management in mining

Introduction

With our country experiencing another cyclic El Niño weather event, water use, water management and the competition for water will no doubt be brought in the minds of the public. Current conflict over state water licences within the Murray Darling basin will become more acerbic in its nature and mining will be pitted against agriculture as protagonists in the fight for water and its use.

As the shown below in a graph produced by the ABS on water usage by state and by industry, mining is definitely a minor player in the water utilisation competition. In addition to this, most mining operations manage their water resources against a well-conceived plan. However, as we know much of this information becomes lost when water becomes in short supply.

Regardless of the current water utilisation table, over the next two to three years the entire available water resource will most likely be reduced, and water saving plans must be enacted.

Understanding El Niño

El Niño is the warming of the ocean surface, or above-average sea surface temperatures (SST), in the central and eastern tropical Pacific Ocean.  Over Indonesia, rainfall tends to become reduced while rainfall increases over the tropical Pacific Ocean.  The low-level surface winds, which normally blow from east to west along the equator (“easterly winds”), instead weaken or, in some cases, start blowing the opposite direction (from west to east or “westerly winds”). For Australia this normally means a period of long, hot and dry weather.

El Niño is variable in its intensity dependant on atmospheric conditions. During an EL Niño climatic cycle, rainfall in Australia is most often reduced significantly and temperatures rise, this reduces water in reservoirs and increases evaporation.

Water access and actions

A recent paper produced by the University of Queensland suggests more climate-focussed research should be commissioned by Queensland miners (who are currently in the grip of a long dry spell) with a view to enabling a shift in actions as the Southern Oscillation produces opposing climatic conditions.

Specifically in the Bowen Basin, two key points were surmised:

  • Adapt to the current variations in the climate
  • Encourage greater interaction and involvement with climate change

The water management plan should the following areas of the mine;

  • Deposit extraction

Right now, extractive industries will be reviewing the water plan with a focus on preservation and recovery. Questions that should be asked and answered include:

  • What actions are able to be taken to reduce the volumes of water over the entire process?
  • Can dust suppression systems be modified or augmented to reduce water or is it possible to reconfigure the layout to capture the water that is used?
  • Is it possible to reduce process water in the wash plant?
  • Can dewatering systems be improved to deliver a dryer product?
  • Can thickeners be optimised to deliver denser underflow and water recovered earlier in the process?
  • Can alternative technologies be implemented to deliver dryer tailings solids and clearer water for reuse?
  • Is it possible to instigate dry stack tailings?

These exercises are not redundant because the lessons learnt and the improvements made will definitely be utilised during the next El Niño event. Once formalised as a plan, it is more readily implemented at the next iteration of climate change, which may be more severe.

While there is no way to know the severity of the impact, being prepared for either weather event (El Niño or La Niña) is crucial for site longevity.

Impacts on production and revenue

Some mining and quarrying operations are relatively dry operations but as resources dwindle, water becomes a key component of the upgrading process to enable poorer resources to be developed to higher productive levels. Lower emissions required of coal-fired power stations rely on cleaner coal and water is a key component of clean coal technologies.

The clearest example of water affecting production is where water is restricted either because it is physically not available or because it is subject to usage licences and quotas. In either case, the options are to restrict production or purchase water.

Droughts or Floods?

Just as today is about planning for El Niño, tomorrow will be managing La Niña.  La Niña events are the reverse of El Niño, with a sustained cooling of these same areas. These changes in the Pacific Ocean and its overlying atmosphere occur in a cycle we commonly call the Southern Oscillation. As you might have guessed, cooler temperatures are often accompanied by intense low pressures which bring rain- lots of rain.

The bottom line is variability. Australian native species are specialists in variability and so must we be in our planning and actions when managing that most precious of resources, water.

As an example, the Wentworth Group commissioned a study which compares the variability of water in Australia to other countries. Of the major rivers in Switzerland, China, Sudan and the USA the greatest variability was the Potomac River, which has a ratio of maximum annual flow to minimum annual flow of 3.9. In Australia’s richest operating coal basin, the Hunter River has a ratio of 54.3.

What this means is our extractive industries are evolving to manage variability, to be flexible and nimble. During La Niña periods for example our plans and actions now concentrate on being able to store and process excess water. The challenge is in each cycle be mindful of the next cycle and develop a sustainable means of managing the excess water in times of flood as if it is a valuable resource, critical when the droughts turn up, which they invariably will.

Conclusion

The key is not to think of climate change in the abstract, or of a circumstance that is in the distance and getting closer. Australia is a land of variability and has been that way for a very long time. The management practices and the technology we develop and implement   should be flexible enough to enable the operation to manage all three phases of Southern Oscillation – the El Niño, the neutral and the La Niña.

References

http://www.bom.gov.au/climate/enso/

http://www.bom.gov.au/climate/enso/Niñocomp.shtml

http://www.bom.gov.au/climate/influences/timeline/

http://www.abc.net.au/news/2017-03-07/state-of-environment-report-warns-climate-change-irreversible/8330582

http://www.theaustralian.com.au/business/wall-street-journal/likely-el-Niño-bad-news-for-poor-pacific-nations/news-story/d24c03367194f9448a8a62bda82ea67c

http://www.miningweekly.com/article/drought-likely-to-pose-water-challenges-for-mines-in-the-medium-term-2016-03-18/rep_id:3650

https://www.nccarf.edu.au/sites/default/files/attached_files_publications/Sharma_2013_Extractive_resource_development.pdf

http://www.abs.gov.au/ausstats/abs@.nsf/Previousproducts/4610.0Main%20Features22012 3?opendocument&tabname=Summary&prodno=4610.0&issue=2012-13&num=&view=

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