Water Policy

Climate variability and water availability

Australia is not "running out of water", but it is not always available when and where people need it. Climate, normal seasonal variations, droughts and floods can all contribute to local extreme conditions.

Climate is the driver of the water cycle. It determines how much water is available (supply) and how much water we need (demand) in the short and long term. Australia is relatively arid, with 80% of the land having < 600 mm rainfall per year and 50% of the land area having <300 mm per year. A key feature of Australia's climate is not necessarily the amount of rainfall but the variability in rainfall from year to year and season to season. The erratic climate is most visible in the cycle of extreme events such as floods (Figure 1) and droughts (Figure 2). Hence, climate variability and climate change will shape the nature of Australian water availability, in terms of:

  1. Extreme rainfall and flood: The combined impact of rising sea levels and extreme weather events are likely to result in increasing occurrence and severity of high rainfall and flood events in some parts of the country (Figure 1). Research shows that with a 20cm sea level rise, damage costs associated with flooding would increase by up to 50%. Despite forecasts for decreased rainfall in many areas of Australia, research by CSIRO (2004) predicts that by 2040, climate patterns for the eastern coast of Australia are likely to bring about more intense and more frequent extreme rainfall events. The most vulnerable regions for extreme rainfall include Coffs Harbour, Coolangatta, north of Brisbane, and over mountainous terrain (CSIRO 2004).

    2. map showing the extent of high rainfall and flood events
    Figure 1: The extent of high rainfall and flood events (Data supplied from the Australian Bureau of Meteorology)

  2. Drought: Increases in occurrence and severity of drought events are expected across eastern and southern Australia, with the most severe events occurring in northeastern and southeastern Australia (Figure 2). Trends in increased drought are already being experienced in southern parts of Australia, whereby the 2002 drought was recognised as being the most severe drought since 1950. This severity of drought has implications on water availability and has resulted in water restrictions across the country.

    3. map showing the extent of drought event
    Figure 2: The extent of drought event (Data supplied from the Australian Bureau of Meteorology)

  3. Temperature: Climate change is predicted to make significant changes to daily maximum temperature across Australia. Figure 3 shows an annual warming of between 0.5oC and 2.5oC during 2005. Unseasonally warm weather occurred in early 2005, with April being the warmest for the past century over much of the country.

    4. map showing the extent of temperature anomalies
    chart showing the extent of temperature anomalies
    Figure 3: The extent of temperature anomalies (Data supplied from the Australian Bureau of Meteorology)

Relevant Links

Bureau of Meteorology (BOM)
BOM Climate Change
CSIRO Climate Change
Department of the Environment and Heritage SoE 2001 Atmosphere Theme Report
Land and Water Australia Managing Climate Variability Program
Queensland Government Long Paddock
Global Energy and Water Cycle Experiment (GEWEX)
International Panel on Climate Change (IPCC)

References

CSIRO, 2004. Hotter summers, fewer frosts for Australia. CSIROnline media release Ref 2004/06, Jan 2004.CSIRO, 2004