Drought in Australia

Drought in Australia is defined by the Australian Bureau of Meteorology as rainfall over period greater than three-months being in the lowest decile of what has been recorded for that region in the past.^[1] 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.^[2] 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.^[3] Bureau of Meteorology records since the 1860s show that a 'severe' drought has occurred in Australia, on average, once every 18 years.^[4] State Governments are responsible for declaring a region drought affected and the declaration will take into account factors other than rainfall.^[1]

Australia has experienced a marked decrease in precipitation levels since 1994.^[5] Deficiencies in northern Australia increased in 2013–14, leading to an extended drought period in certain parts of Queensland. Between 2017 and 2019, severe drought developed once more across much of eastern and inland Australia including Queensland, New South Wales and Victoria, also extending into parts of South and Western Australia.