Water Book

  1. Overview
  2. Foreword
  3. Contents, Acknowledgements
  4. Introduction
  5. Chapter 1: Current water availability and use
  6. Chapter 2: Water values
  7. Chapter 3: Water and climate
  8. Chapter 4: Groundwater
  9. Chapter 5: Water quality
  10. Chapter 6: Urban water sustainability
  11. Chapter 7: Future urban water supplies
  12. Chapter 8: Irrigation
  13. Chapter 9: Water for the environment
  14. Chapter 10: Water in mining and industry
  15. Chapter 11: Conclusions
  16. Endnotes, Index

Chapter 3: Water and climate

Page 7 of 16

A road cut off by floodwaters, with cars and people in the foreground.

By Francis Chiew and Ian Prosser

Floods, droughts, and climate change are the three most important influences of climate on Australia’s water resources.

Overview

Water resources are vulnerable to both climate variability and change; for example, runoff into Perth’s reservoirs has declined by 55 per cent since the 1970s and the 1997 to 2009 drought resulted in unprecedented decline in runoff and water use in the southern Murray–darling Basin.

Climate change has played a part in recent reductions in rainfall and water resources, however its specific contribution is difficult to quantify.

Climate change by 2030 is likely to reduce average river flows by 10 per cent to 25 per cent  in some regions of southern Australia but further climate change could produce even more profound reductions of water resources in southern Australia.

The relationships between climate and runoff are now being used to provide more accurate seasonal forecasts of water resources useful for irrigators, dam operators, and environmental managers.

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Interview with chapter co-author Francis Chiew

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Transcript

The three main influence of climate on water resources are floods, droughts, and climate change. These occur over different time scales. For example, floods occur over a couple of days; droughts are dry conditions that persist over years or decades, like in the recent millennium drought where river flows were less than half the long term average. While climate change will further influence this through changing the average long term conditions, as well as the characteristics of floods and droughts.

We know that climate change impact will be amplified in the river flows, for example a change in rainfall will be amplified as a two or three bigger percentage change in stream flow. Higher temperatures will also increase the potential for evaporation, and this has the potential to further reduce river flows.

Now we carried out modelling studies across CSIRO, as well as elsewhere, looking into using global climate models, downscaling models, hydrological models, and this showed that our future is likely to be drier in southern Australia, where we can expect a water decline by about ten to 25 per cent in the south of the Murray-Darling Basin, in Victoria, and the south-west western part of Australia by say around 2030.

Now of course when this happens we will continue to have large variability, we will continue to have floods and droughts, but a change in long term average condition will mean that the droughts that we have seen in the past will occur more frequently, and can be potentially more severe.

Water resources adaptation to climate change is already happening in Australia. A lot of these are driven not by climate change alone, but by a whole series of other pressures or other drivers. For example the City of Perth has to adapt to a climate shift that occurred in the mid 1970s, Melbourne on the other hand has to adapt to the long prolonged drought, projections of a drier future, as well as population growth. Now these cities are looking at more secure water supply sources, so these include desalination plants, as well as water reuse options or schemes, and also looking into (indistinct words – 2:19) to reduce water use.

In the regional areas it’s a bit different. These are driven by pressures of projections of a drier future because of climate change and also other drivers, and also from wanting to redress the balance between irrigation water use and environmental water use. So in the regional areas billions of dollars have been spent to upgrade irrigation systems, to buy back water to irrigation water entitlements, and also one of the biggest things that’s happening is developing future water plans that can cope with the current climate, as well as future climate.

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