Rainfall deficiencies

A mob of sheep raises dust north of Dubbo, New South Wales, during drought. Photo by Department of Foreign Affairs and Trade Australia is a large continent containing many different climate zones, from wet tropics in the north, arid and semi-arid conditions in the interior, and alpine climates in the south-east. Each climate zone is influenced by very different large-scale, predominant weather and climate patterns. For this reason, at any time different parts of the Australian continent can be affected by very different climate extremes. An example of this occurred in 2010, where southwest Western Australia experienced its driest year on record, in contrast to the rest of Australia, which received above-average to very-much-above-average rainfall.

Use our Drought Statement, rainfall maps and reports to watch for areas with significant long and short-term rainfall deficiencies.

Updated on 5 August 2015

Deficiencies increase slightly in the east, develop in southwest Western Australia

July rainfall was below average for most of the South West Land Division in Western Australia, extending into part of the Southeast Coastal district. The month was also drier than average for much of Tasmania, coastal regions of southeastern Queensland and central New South Wales, large parts of South Australia, and western to central Victoria. The southern wet season, which spans April to November, continues to track below average rainfall for the season so far in central to western Victoria, southeastern South Australia, Tasmania, and across the greater southwest of Western Australia.

Compared to the last Drought Statement, deficiencies have generally remained similar to those for the preceding period or have increased slightly in areal extent and severity. The most notable increases have been in Queensland, western to central Victoria (at the 13-month, July 2014 to July 2015, timescale), parts of coastal Tasmania, and the west coast and adjacent inland of the South West Land Division in Western Australia. Serious or severe rainfall deficiencies have been observed in parts of the southeast for various medium-term periods since late 2013, and for longer-term deficiencies for various periods to around 2 years duration. Deficiencies are also evident over large areas of eastern Australia for periods of about 3 years' duration.

At the shorter term, rainfall deficiencies have continued to build over the southwest of Western Australia with severe deficiencies (lowest 5% of historical records for similar periods) now in place across a large area at the 3-month timescale (May–July 2015). A number of locations within this region have seen record-low falls.

3-month rainfall deficiencies

Despite some recent heavy falls across the Central Wheat Belt district in Western Australia at the close of July, rainfall deficiencies have emerged at the 3-month timescale (May to July 2015). Below-average rainfall during recent months followed a good start to the growing season with above-average monthly rainfall during April. The growing season spans April–November, with the bulk of the rain received in the cooler months of the year. However, daily totals as high as those received in the wheat belt between 29th July and 1st August are unusual for the region and the time of year.

Severe deficiencies (lowest 5% of historical records for similar periods) for the period cover much of the South West Land Division in Western Australia and some smaller areas further inland. Small pockets of deficiencies are also seen in parts of northern Australia, although this period typically corresponds to the dry season there.

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13-month rainfall deficiencies

For the 13 months July 2014 to July 2015, severe or serious deficiencies (lowest 5% or lowest 10% of records) persist in areas of northern Queensland extending across the southern and central Cape York Peninsula, roughly from Kowanyama to Townsville, along the southern coast of the Gulf of Carpentaria, and in an area of inland central Queensland near Longreach. Deficiencies have increased slightly compared to the previous period, although July rainfall is typically low in most of northern Queensland.

A substantial area of lowest-on-record rainfall was observed in southeastern South Australia and western Victoria, with serious or severe deficiencies also present along a broad band extending from west of Ceduna in South Australia, into the western edge of the Northeast district of Victoria. Much of southeastern Australia has seen below-average April–November rainfall during three of the last four years, with monthly rainfall also below average from August last year for much of this region (apart from well-above-average January rainfall, and above-average March and May rainfall in Tasmania). Deficiencies increased in extent slightly in northwestern Victoria. Deficiencies also increased in western and northwestern Tasmania and on the west coast of southwestern Western Australia.

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34-month rainfall deficiencies

At the 34-month timescale (October 2012 to July 2015), rainfall deficiencies have increased slightly in both extent and severity in some parts of central to northern Queensland. Serious and severe deficiencies are in place from the base of the Cape York Peninsula, extending through central Queensland into parts of central southern Queensland and northern New South Wales to the west of the Great Dividing Range.

Deficiencies have also increased in extent in western to central Victoria while increasing in severity in southeastern South Australia and have emerged in parts of the central South West Land Division in Western Australia.

Deficiencies also persist at a range of even longer timescales, with most of eastern Australia having received below-average rainfall following the conclusion of the 2010–12 La Niña events.

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Soil moisture

Soil moisture in the upper layer for the week ending 26 July had increased across the Pilbara and the region around Derby in the Kimberley, both in Western Australia, and parts of the Cape York Peninsula in Queensland, while generally decreasing across the rest of Australia, compared to the week ending 28 June.

Upper-layer soil moisture at the end of July was below average for much of the South West Land Division in Western Australia, although rainfall in the last days of July has likely raised soil moisutre in parts of this area. Soil moisture was also below average in parts of the eastern Kimberley and Victoria River district of the Northern Territory, as well as smaller areas of the coastal Roper–McArthur district of the Northern Territory and large parts of the Alice Springs district and adjacent parts of Queensland. Soil moisture was also below average in numerous pockets along the east coast of Queensland and New South Wales, between southeast South Australia and South Gippsland in Victoria, and across eastern to central Tasmania. Soil moisture was above average across the eastern Top End, a large area of the Pilbara and western Gascoyne in Western Australia, and in a large area of inland eastern Australia between far eastern Victoria and southern Queensland.

Lower-layer soil moisture for the week ending 26 July was generally similar to that for the week ending 28 June, although having decreased slightly in Western Australia and moving slightly closer to average values in eastern Australia.

Lower-layer soil moisture was above average for most of the northwest and interior of Western Australia, the central to southern Northern Territory, scattered areas along the east coast, eastern Victoria, and parts of South Australia but not the southeast. Soil moisture was below average in most of the northern half of the South West Land Division in Western Australia, extending just into the Goldfields District, and also for areas of coastal northern Queensland, around the Gulf coast, parts of the Top End, some areas between central Queensland and northern New South Wales, and much of central to western Victoria and southeastern South Australia.

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This section displays rainfall maps. Current drought status is described in the previous section. For historical drought status statements, go to archive of drought statements

These maps are also available from Maps - recent conditions

Weekly rainfall updates

The Weekly Rainfall Update describes rainfall over the previous week. It includes a map and a summary table of the highest weekly totals. A discussion of the impact of recent rains on rainfall deficiencies is also presented.

Rainfall and temperature outlooks

Current map, small viewRainfall and temperature outlooks outline likely conditions over three-month periods. Outlooks are available for single months, three months, and for any location in Australia. Formats include text summaries, maps, graphs and video.
Rainfall and temperature outlooks: Outlooks
Previous outlooks: Archive of outlooks Archive of outlook maps

Seasonal streamflow forecasts

Australian streamflows are among the most variable in the world. Seasonal streamflow forecasts extends water management decision making capability. Forecasts are issued monthly.

Climate statements archive

The archive includes previous monthly, seasonal and annual climate summaries for nation-wide, state/territory and capital city conditions.

Maps of recent conditions

CSIRO water balance maps

Small image of water balance mapCSIRO (AWAP) Water balance maps include maps of soil moisture and water fluxes contributing to changes in soil moisture (rainfall, transpiration, soil evaporation, surface runoff and deep drainage).

What is drought?

Drought is a prolonged, abnormally dry period when the amount of available water is insufficient to meet our normal use. Drought is not simply low rainfall; if it was, much of inland Australia would be in almost perpetual drought. Because people use water in so many different ways, there is no universal definition of drought. Meteorologists monitor the extent and severity of drought in terms of rainfall deficiencies. Agriculturalists rate the impact on primary industries, hydrologists compare ground water levels, and sociologists define it by social expectations and perceptions.

It is generally difficult to compare one drought to another, since each drought differs in the seasonality, location, spatial extent and duration of the associated rainfall deficiencies. Additionally, each drought is accompanied by varying temperatures and soil moisture deficits.

Rainfall averages, variability and trends

Median rainfall map, links to climate average maps An area experiences a rainfall deficit when the total rain received is less than the average rainfall for that period.

Definitions

Lowest on record - lowest since at least 1900 when the data analysed begin.
Severe deficiency - rainfalls in the lowest 5% of historical totals.
Serious deficiency - rainfalls in the lowest 10% of historical totals, but not in the lowest 5%.

Very much below average - rainfalls in the lowest 10% of historical totals.
Below average - rainfalls in the lowest 30% of historical totals, but not in the lowest 10%.
Average - rainfalls in the middle 40% of historical totals.
Above average - rainfalls in the highest 30% of historical totals, but not in the highest 10%.
Very much above average - rainfalls in the highest 10% of historical totals.

Acknowledgements

Front page photo, provided by Department of Foreign Affairs and Trade: 'A mob of sheep raises dust north of Dubbo, New South Wales, during drought'