Rainfall reduction of SW Australia

A news story was published in mid 2017, the headline was "State and Federal Governments in talks over drought relief for WA farmers"  The story detailed the drought conditions being experience in parts of the WA wheatbelt region (historically Australia's most reliable wheat growing region). I wanted to briefly explore this story some more.

The majority of the rainfall in SW Western Australia occurs during the winter months of June, July and August, with much less through the summer months. The winter rainfall through Western Australia has decreased by 20% since 1960. This reduction in rainfall has led to a 40% drop in level of influx of rainfall into dams. Figure 1 shows the measured reduction in rainfall from the period of 1925 - 1975 to 1975 - 2003, in Southwest WA.

Figure 1. Measured monthly rainfall for southwest WA for before and after 1975. 

The mechanisms which have resulted in this decrease in rainfall are multi-faceted, including; land use change, ocean temperatures and circulation changes, as well as natural variability and continue to be researched. 

 Projections based on the IPCC scenarios show a continued decrease in rainfall through the 21st century of ~20% (Fig. 2), from levels of 1981- 2000 compared to 2081 - 2100.

Figure 2. Showing the % level of Rainfall through Australia under RCP5 CMIP5 projections using the GPCC V7. The cross-hatched area shows areas of uncertainty.

The drought experienced this year is not an isolated event but a part of a prolonged decline (Fig.1), which will continue into the future (Fig.2). This phenomenon of drop in rainfall shows one of the many, sometimes overlooked ways in which an anthropogenic induced climate change will directly affect the populations of economically developed countries, who often can seem further removed from the most severe consequences of climate change.


Comments

  1. Unknown9 January 2018 at 10:14

    I spent my year abroad out at the University of Western Australia, and this is the hot topic out there. The governement of WA has made a decision to solve their water supply problem by developing supply-side solutions, and their success, has reduced the perception of water crisis, but in reality may be causing significant other problems - their behaviour hasn't changed. Can only imagine that the effects of drought will become more severe in WA.

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