How we manage water resources in a changing climate
We use the latest climate information to assess how the state’s water resources are and may be impacted by climate change in the future.
We do this to:
- manage for secure and reliable water supplies
- maintain rivers and wetlands.
Western Australia has been getting hotter since the 1960s and we have experienced changing weather and rainfall trends which impacts on water availability. The south west is getting drier while rainfall across other parts of the state was more variable.
How we use climate models to manage water resources
We use data from global climate models to show how rainfall may change in the future and this informs how we manage Western Australia’s water resources.
While we can’t predict climate or rainfall in each year, we can use climate projections to show a range of possible climate futures at different locations and time horizons (e.g. 2030, 2050, 2070 and 2100).
We use the data to identify the risks of different climate futures to water resources, and this informs our water planning, flood advice and management of water-dependent ecosystems.
Climate trends in Western Australia
Western Australia is a large state with diverse climatic influences and varied weather. We have summarised data from global climate models for different climatic regions – Kimberley, Pilbara, Central, Central West and South West.
The future projections for rainfall for each region are expressed as a percentage change or anomaly relative to the World Meteorological Organisation’s 1961–1990 baseline period.
How confident are we in the future?
Over 90 per cent of the global climate models for the South West and Central West regions suggest a hotter, drier future. Rainfall across the South West and in some areas of the Central West has been steadily declining since the 1960s because of a southward shift of winter storm systems, and a greater frequency of high pressure systems – which usually result in clear skies and light winds.
Scientists at the Bureau of Meteorology and CSIRO have linked changes in rainfall and temperature in the South West to increasing global temperatures and shifts in atmospheric circulation in the Southern Hemisphere. Scientists from around the world recognise the South West as an area that is highly sensitive to declining winter rainfall because of its latitude and location on the western side of a large landmass.
The global climate model results for the Kimberley, Pilbara, and Central regions, however, vary widely and there is no clear trend from the models towards increasing or decreasing rainfall. Looking to 2030, differences in rainfall from year-to-year are likely to have a more noticeable effect on water resources in these regions compared to a long-term climate shift. The simulations of future climate for these regions are so variable because of the difficulty of modelling the start of the monsoon, the Madden-Julian Oscillation (an eastward pulse of cloud and rainfall near the equator), circulation patterns from the tropics and the effects of rainfall drivers from eastern Australia (like the Southern Annular Mode and the El Niño–Southern Oscillation)