Drought in Australia

Drought in Australia is defined by the Australian Bureau of Meteorology as rainfall over a three-month period being in the lowest decile of what has been recorded for that region in the past. This definition takes into account that drought is a relative term and rainfall deficiencies need to be compared to typical rainfall patterns including seasonal variations. Specifically drought in Australia is defined in relation to a rainfall deficiency of pastoral leases and is determined by decile analysis applied to a certain area. Note that this definition uses rainfall only because long-term records are widely available across most of Australia. However, it does not take into account other variables that might be important for establishing surface water balance, such as evaporation and condensation.

Historical climatic records are now sufficiently reliable to profile climate variability taking into account expectations for regions.Bureau of Meteorology records since the 1860s show that a ‘severe’ drought has occurred in Australia, on average, once every 18 years.State Governments are responsible for declaring a region drought affected and the declaration will take into account factors other than rainfall.

The worst drought to affect the country occurred in the 21st century—between the years 2003 to 2012. Nonetheless, many regions of Australia are still in significant drought and rainfall records have showed a marked decrease in precipitation levels since 1994, with many scientists attributing this to climate change and global warming. Deficiencies in northern Australia increased in 2013–14, leading to an extended drought period in certain parts of Queensland.

Since 1860, when adequate meteorological recording commenced, the most severe droughts have occurred commonly at intervals of 11 to 14 years. Major droughts that were recorded later in the 19th century include:

At the time of Federation, Australia suffered a major drought. There had been a number of years of below average rainfall across most of Australia before the drought. During the drought the wheat crop was "all but lost"; and the Darling River was dry at Bourke, New South Wales, for over a year, from April 1902 to May 1903. There was concern about Sydney's water supply. By 1902 Australia's sheep population dropped from its 1891 level of 106 million to fewer than 54 million. Cattle numbers fell by more than 40 per cent. Sheep numbers did not return to 100 million until 1925.

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