Soil moisture details are reported when there are periods of significant rainfall deficits.
Soil moisture data is from the Bureau's Australian Water Resources Assessment Landscape (AWRA-L) model, developed through the Water Information Research and Development Alliance between the Bureau and CSIRO.
See: Australian Landscape Water Balance.
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
- Average rainfall: How much rain do you expect?
- Rainfall variability: How consistent is rainfall in your area?
- Rainfall history: Check tables, graphs and data from your local weather station.
- Rainfall trends: Has your rainfall changed?
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.
Rainfall deficiencies continue in the east
August rainfall was below average through the northern Gascoyne, Pilbara and central parts of the Interior District in Western Australia; western inland, central, and northern coastal regions of Queensland; most of New South Wales (apart from the central northern inland regions); much of eastern South Australia; and Victoria away from the southwest. Rainfall was very much below average (ranked in the lowest 10% of records) for areas of the north tropical coast of Queensland, large areas of lower western New South Wales, and the southern interior of Western Australia.
August rainfall was above average across large parts of southern Western Australia; coastal and central South Australia; southeastern South Australia and western Victoria; western Tasmania; Arnhem Land in the Northern Territory; and scattered pockets along the Gulf Country coast and Cape York Peninsula in Queensland.
During the third week of the month, a low pressure system tracked across from the Great Australian Bight to southwestern Queensland and produced moderate falls through coastal and central regions of South Australia, the Maranoa and Warrego District of Queensland, and northern areas of the North West Slopes and Plains District of New South Wales. This event has eased rainfall deficiencies somewhat at the 5-month timescale in these areas.
The rainfall along the southern coastal regions of the mainland and western Tasmania was mostly attributed to the passage of several vigorous cold fronts, associated troughs and rainbands during the month. Deficiencies have reduced at the 5-month scale through large areas along the southern coast and western Goldfields District of Western Australia; the southwest corner of the Northern Territory and adjacent corner in South Australia; and also through western parts of the Eyre Peninsula region of South Australia over all three timescales.
Deficiencies have increased slightly in both extent and severity at the 8- and 17-month timescales for almost all of New South Wales, inland southern Queensland, and some areas in eastern South Australia, and northwestern and eastern Victoria.
5-month rainfall deficiencies
The southern rainfall season spans April to November and corresponds to the southern agricultural cropping season. For 2018, the southern rainfall season has so far seen 5 consecutive months of below average rainfall across much of Australia. Serious or severe rainfall deficiencies persists in a large area along and inland of Western Australia's southern coast, extending into the southern Goldfields District; Central Australia; large parts of Queensland; and most of New South Wales, and adjacent eastern South Australia.
As a result of the rainfall during August, deficits have reduced in severity in the Maranoa and Warrego districts of Queensland and over the border into the North West Slopes and Plains district of New South Wales. However, the accumulated rainfall deficits over the past several months in these areas are very large, and will require a great deal more rain over an extended period of time to remove them completely.
8-month rainfall deficiencies
Rainfall during August was not enough to lessen deficiencies at the 8-month timescale. Compared to the previous Drought Statement, deficiencies have mostly continued and intensified through those areas already affected.
Recent rainfall has, however, seen the lessening of deficiencies through southern South Australia and to a lesser extent along the southwest coast of Western Australia. However, serious or severe deficiencies remain for most of the northeastern Agricultural and Pastoral districts of South Australia.
17-month rainfall deficiencies
For the 17 months starting April 2017, rainfall deficiencies have increased over large parts of New South Wales, eastern Victoria and southwestern Queensland. Serious or severe deficiencies continue to affect most of the northern two-thirds of New South Wales (away from the northeast coast and southern border); central and southern Queensland; southern Northeast Pastoral and Murraylands districts of South Australia; and coastal areas of the Southwest Land Division in Western Australia.
Rainfall along the southern coastline during the past month has largely cleared deficiencies over most of the Eyre Peninsula in South Australia at this timescale, and eased deficiencies in small pockets of the Southwest Land Division in Western Australia.
August rain has moistened the soil at the lower-layer (from 10 cm to 100 cm deep) in some southern regions. Much of the southern half of Western Australia (apart from the Goldfields and southeast coastal regions); the southwest corner of the Northern Territory; most of western South Australia; southwest Victoria, and much of Tasmania have seen soil moisture increase from below average to average, and even above average in some areas.
The combination of rainfall deficiencies, warm temperatures, wind and high potential evaporation has contributed to persistently dry soils across the eastern half of South Australia away from the southeast coast; much of New South Wales; and northern and eastern Victoria. Soil moisture has decreased compared to last month over much of inland New South Wales, the southern and Central Highlands of Queensland and in Gippsland in Victoria.
Year-to-date (January to August), mean maximum temperatures across Australia are the highest on record. Associated with the warm temperatures, strong winds, and low humidity, total pan evaporation averaged across Eastern Australia has been highest on record for five of the first eight months of the year.
- August rainfall was below average for large areas of eastern Australia
Rainfall deficiencies have increased:
- in parts of New South Wales and inland Queensland at the 5-month timescale
- for most of New South Wales, southwestern Queensland and eastern Victoria at the 8- and 17-month timescales
- Lower-level soil moisture was below average for August through the northern and eastern mainland
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