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.
Below average autumn rainfall for southern mainland; rainfall deficiencies increase in New South Wales
May was an exceptionally dry month for Australia. Nationally, May rainfall was the third-lowest on record, and lowest for May since the record set in 2008. Monthly rainfall was below average for most of Australia, and in the lowest 10% of historical observations (decile 1) for May for large areas of southern Western Australia, northern and eastern New South Wales, and southern Queensland.
Low May rainfall has also continued the dry start to the southern wet season for southern Australia. The southern wet season spans April to November, and corresponds to the southern agricultural cropping season.
The start to the wet season has been particularly dry for the south of Western Australia; deficiencies have emerged along the southern coast of that State at a range of timescales following decile 1 rainfall during May.
A large number of stations in New South Wales received record low May rainfall or their lowest May rainfall for at least 20 years. Coming on the back of existing significant rainfall deficiencies in the previous Drought Statement, this has further increased deficiencies across much of New South Wales at both the 5- and 14-month timescales.
Conversely, May rainfall was above average for parts of southern Victoria, particularly the southwest, and in parts of western, central, and southeastern Tasmania. Rainfall deficiencies have decreased in these areas. However, serious to severe deficiencies persist in Gippsland at both timescales, and along the east coast of Tasmania at the 14-month timescale.
5-month rainfall deficiencies
Below average rainfall for May has deepened rainfall deficiencies across the much of New South Wales, while serious deficiencies have also emerged in the South Coastal District of Western Australia. Above average rainfall for May has lessened deficiencies across southeastern South Australia and much of southern Victoria.
The year so far has been drier than average for the southeastern quarter of the mainland; for this region January to May 2018 has been the seventh-driest such period since 1900 at least. For autumn alone, rainfall across southern Australia was the second-lowest on record, and a number of stations in both New South Wales and Western Australia observed record-low autumn rainfall.
For the five months from January to May, serious to severe rainfall deficiencies are in place across much of New South Wales (except for the southeast and the northern coasts); adjacent areas of southern Queensland and eastern South Australia; a large part of southeastern South Australia around the Murraylands and Upper South East districts; and smaller areas of Gippsland in Victoria, about Lake Eyre / Kati Thanda in South Australia, and in Western Australia in the South Coastal District and near Shark Bay on the west coast.
14-month rainfall deficiencies
Compared to the 13-month period discussed in the previous Drought Statement, rainfall deficiencies have increased in southwest Western Australia, South Australia, New South Wales, and southern Queensland.
For the 14 months from April 2017 to May 2018, serious to severe rainfall deficiencies are in place across large areas of New South Wales (away from the southern border and northeastern coast); large areas of southern to central Queensland; across much of Gippsland in eastern Victoria; parts of South Australia about Lake Eyre / Kati Thanda, Ceduna, and Gulf St Vincent; around the coast of Western Australia from Karratha to Bremer Bay; and along the east coast of Tasmania.
Soil moisture in the lower layer (from 10 cm to 100 cm deep) for May decreased over most of Australia.
Lower-layer soil moisture was below average for most of Western Australia, South Australia, New South Wales, northern and eastern Victoria, southern and central eastern Queensland, and large parts of the Northern Territory.
Soil moisture was above average across large parts of northern and western Queensland.
- Third-driest May on record for Australia
- Rainfall for the month below average in most areas, except parts of the southeast
- Rainfall deficiencies persist in both the east and west of the country, increasing in New South Wales at the 5- and 14-month timescales
- Lower-layer soil moisture was below average for May across most of the southern mainland, the Kimberley, Northern Territory, and parts of eastern Queensland
Product code: IDCKGD0AR0