Rainfall distribution

Australia is a dry country with highly variable rainfall. The table below lists the average rainfall for each of the states and territories for the calendar years 2003 to 2005 and for the year of the assessment, 2004–05. The maps provided below highlight both the spatial and temporal variability of Australia’s rainfall. The long-term average annual rainfall across Australia varies from less than 300 mm in most of central Australia to more than 3000 mm in parts of far northern Queensland.

For 2004–05 rainfall in Australia was estimated at 2,789,424 gigalitres, most of which fell in Queensland (865,973 gigalitres), Western Australia (639,609 gigalitres), and the Northern Territory (505,623 gigalitres). During this time, very dry conditions were experienced across much of Australia. In 2004–05, a significant proportion of the Western Plateau and Lake Eyre drainage divisions received less than half of the mean annual rainfall. In contrast, rainfall was close to average in the South West Coast drainage division, northern and southern regions of the Murray-Darling Basin, and the South East Coast drainage division.

Annual rainfall for Australia and the states and territories from 2003 to 2005 and the longer term average from 1961-1990 (normal values are calculated using 1961–90 averages)

Source: Bureau of Meteorology

Australian annual mean rainfall (mm) 1900 to 2005 (Source: Bureau of Meteorology)

Annual average rainfall across Australia, based on a standard 30 year climatology record (1961-1990) (Source: Bureau of Meteorology)

Total rainfall for July 2004 – June 2005 (Source: Bureau of Meteorology)

Percentage of mean annual rainfall for July 2004 – June 2005 (Source: Bureau of Meteorology)

Rainfall decile ranges across Australia for (a) 10-year period starting in early 1997 and (b) 5-year period starting in 2002 (Source: Australia’s water supply status and seasonal outlook, NWC October 2006)

During the year of interest for the water balances (1 July 2004 to 30 June 2005), Australia received below-average rainfall across most of the country. Furthermore, the 2004–05 year was preceded by more than five years of below-average rainfall across large parts of Australia, particularly the eastern states and south-west Western Australia.

A few areas experienced above average rainfall, particularly around Carnarvon, Western Australia (in the Indian Ocean drainage division), where 215 mm fell in July 2004, almost matching the annual average of 226 mm. Higher than average rainfall in parts of northern New South Wales in the Murray-Darling Basin in late 2004 contributed to higher than average rainfall in that region.

Much of southern Australia and coastal Queensland has experienced a decrease in annual rainfall since 1997, which has most severely affected the eastern states and the south-west corner of Western Australia. A second, more widespread downturn in annual rainfall started during 2002 and has severely affected the eastern states.

The low annual rainfalls during 1997, 2002 and 2006 can be attributed to El Niño events that occurred during these years. Earlier El Niño events were commonly followed by good, drought-breaking rains. Rainfall in the years after 1997 has been insufficient to fully alleviate the rainfall deficiencies. One result of this is the low levels of water stored in eastern Australia and south-west Western Australia’s large dams in recent years.

2004–05 summary of rainfall, evapotranspiration, deep drainage, runoff and land use area of Australia

Note: Agricultural land includes dryland farming, irrigated areas and pasture; data sourced from ABS Water Account 2004-05, and Water 2010 project.

For further information on rainfall visit the Bureau of Meteorology Climate website.

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