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.
Driest September on record for Murray–Darling Basin exacerbates deficiencies in eastern Australia
Rainfall in September was below average for most of Queensland south of the Cape York Peninsula, New South Wales, northern and far eastern Victoria, South Australia south of Lake Eyre and east of Ceduna, and eastern Tasmania. Below average rainfall was also observed in the Kimberley and northern half of the Northern Territory, however much of northern Australia away from eastern Queensland is typically seasonally dry at this time of year.
Rainfall was very much below average (ranked in the lowest 10% of records) for a large area of the mainland southeast. For New South Wales as a whole September rainfall was the lowest on record, while for Queensland it was the tenth-driest September since records commenced in 1900. Rainfall deficiencies have increased in both extent and severity across eastern Australia at the 4- and 7-month timescales, most notably in New South Wales and the southern third of Queensland.
Dry conditions have been exacerbated by exceptional warmth across most of the country in September, following on from the warmest winter mean maximum temperature on record. Maxima for Queensland were the second-warmest on record for the month, and the sixth-warmest on record for September for New South Wales since records commenced in 1910.
4-month rainfall deficiencies
Serious to severe rainfall deficiencies are present across an area of South Australia extending from the top of the Great Australian Bight through northern agricultural and southern pastoral districts to the western border of New South Wales; across most of New South Wales except parts of the northwest and northeast; large parts of Queensland between the southern border, Fraser Island, and the Central Coast; an area of central Victoria and East Gippsland; and east coast Tasmania.
Serious to severe rainfall deficiencies for the 4-month period ending September 2017 are present in areas along the northwestern coast between the Gascoyne in Western Australia and the western Top End in the Northern Territory. Rainfall during September alleviated deficiencies in parts of the Gascoyne and across areas further south.
Deficiencies have increased in both areal extent and severity since last month across affected areas of South Australia, Victoria, New South Wales, and Queensland.
7-month rainfall deficiencies
Rainfall deficiencies persist along the west coast of Western Australia between about Exmouth and Perth, although rainfall during September has moderated the severity of deficiencies slightly, and reduced their extent across the southwest of the State. Unseasonal September rainfall in Central Australia has also reduced the extent of deficiencies in the south of the Northern Territory.
Compared to the 6-month period ending August 2017, deficiencies have increased in areal extent in the mainland eastern States. Rainfall deficiencies affect areas of coastal South Australia between the Nullarbor and Eyre Peninsula, East Gippsland in Victoria, the east coast of Tasmania, pockets of central to western New South Wales, and across most of central to southwestern Queensland. However, this is a seasonally dry time across inland Queensland and Central Australia, and little change is expected in these regions until the northern wet season commences in the comming weeks.
High evaporation rates associated with exceptionally warm September days, clear skies, and low rainfall have again seen a month-on-month decrease in lower-layer soil moisture across much of eastern Australia and South Australia.
Soil moisture in the lower layer (from 10 cm to 100 cm deep) for September was below average for most of South Australia (except for coastal areas from the Eyre Peninsula to southeast, and central northern areas); eastern Victoria; eastern Tasmania; nearly all of New South Wales; and most of Queensland south of the Cape York Peninsula (except for parts of the central west and some pockets in the eastern hinterland). Soil moisture was also below average for an area of the Pilbara coast in Western Australia, parts of southern Western Australia, and the far south of the Northern Territory.
Conversely, soil moisture has increased across much of Western Australia and was above average for September in much of the Gascoyne and south of the Interior District, as well as being above average in scattered pockets of Central Australia, west coast Tasmania, and coastal southwestern Victoria.
- Rainfall during September was below to very much below average over much of Australia, and lowest on record for the Murray–Darling Basin as a whole
- Serious to severe deficiencies are present at the 4-month timescale across the majority of New South Wales, parts of southern, central and east coast Queensland, a large area of central southern South Australia, coastal parts of northwest and northern Western Australia and the western Top End, eastern Victoria, and eastern coastal areas of Tasmania
- Serious to severe rainfall deficiencies are evident at the 7-month timescale near the west coast of Western Australia, west coast South Australia, eastern Tasmania, and pockets of eastern Australia from eastern Victoria to central and southwestern Queensland
- Lower-layer soil moisture for September was below average across most of South Australia, Victoria, New South Wales and Queensland, the south of the Northern Territory, eastern Tasmania, and areas of the south of Western Australia
Product code: IDCKGD0AR0