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
Product code: IDCKGD0AR0
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.
For the week to 18 September, rainfall was recorded along the southern coast of Western Australia; across southeastern South Australia and the southern half of Victoria; most of Tasmania; and small coastal pockets of the west and east of the Top End in the Northern Territory and east coast Queensland; with isolated falls in northeast and southeast New South Wales.
At the start of the week, pre-frontal troughs and cold fronts generated light to moderate showers over coastal South Australia and southwest Victoria, with moderate falls reported over western Tasmania until mid-week due to fronts embedded in a strong west to northwesterly flow.
Also during the first part of the week, a surface trough extending through inland Queensland and New South Wales combined with an onshore flow and created isolated thunderstorms and showers along the northeast coast of New South Wales and areas of Queensland's east coast.
Approaching the middle of the week, a cold front extending from a deep low in the Southern Ocean crossed southwest Western Australia, bringing light falls. This front broke up, becoming a complex area of low pressure and fronts as it continued over the Bight and across southern regions of South Australia during the second half of the week, with light falls over southeast South Australia and widespread light to moderate falls recorded over much of the southern half of Victoria. In Tasmania, these systems produced moderate totals over the west of the State.
In the north, humid easterly flow and a weak trough triggered showers and produced light falls over the western Top End of the Northern Territory during the middle of the week.
At the end of the week a weak cold front extended from southwest Western Australia to south of Tasmania, again bringing light falls to far southwest Western Australia and the west of Tasmania.
Rainfall totals exceeding 50 mm were recorded across most of western Tasmania. The highest weekly total was 131 mm at Mount Read in western Tasmania.
Rainfall totals of 10 mm to 20 mm were recorded in parts of the southern coast of Western Australia; far southeastern South Australia; from southwestern Victoria to the Otway Ranges and across West and South Gippsland; and across most of the remainder of Tasmania away from the east coast.
Totals in some Victorian locations exceeded 25 mm, while isolated locations in east coast Queensland, and northeast and southeast New South Wales also received varied totals up to 30 mm.
Little of no rainfall was observed in the majority of Western Australia, the Northern Territory, Queensland, and New South Wales, most of South Australia away from the peninsulas and southeast, and northern Victoria.
Impact of recent rainfall on deficits
The Drought Statement, issued on 5 September 2018, discusses rainfall deficits over Australia for the 5-month (April–August 2018), the 8-month (January–August 2018) and 17-month (April 2017–August 2018) periods. Rainfall deficit maps are available for these periods as well as for standard periods.
The maps below show the percentage of mean rainfall that has been received for the rainfall deficit period for the 5-month, 8-month and 17-month periods ending 18 September 2018.
Rainfall for the period 1 April 2018 to 18 September 2018
Serious or severe rainfall deficiencies persist at the 5-month period 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.
Rainfall in the last week has had little effect on deficiencies.
Affected areas of southern Western Australia, southern and eastern New South Wales, and areas of eastern Queensland have received generally between 30% and 70% of average rainfall for the period. Affected areas of the Northern Territory and across the border into the central interior of Western Australia, northwestern and eastern South Australia, northwestern New South Wales, western and central Queensland have received less than 30% of average for the period.
Rainfall for the period 1 January 2018 to 18 September 2018
Serious to severe rainfall deficiencies for the 8-month period continue across much of western and central New South Wales and adjacent areas of the Darling Downs and Far Southwest Queensland, an area of the Central Highlands and Coalfields District, northwestern Victoria and smaller areas of Gippsland. Deficiencies are still present in a small area in the South Coastal District of Western Australia, and in areas of southeastern South Australia, extending to the Eyre Peninsula, and most of the northeastern Agricultural and Pastoral District of South Australia.
Rainfall during the past week has had little effect on deficiencies.
Affected areas of central and northwestern New South Wales, southwestern Queensland and northeastern South Australia have mostly received below 30% of average rainfall for the period. Affected areas from southwest, and central to eastern New South Wales, northwestern Victoria, southeastern South Australian received 30% to 60% of average for the period, while affected areas in Western Australia received 60% to 70% of the average.
Rainfall for the period 1 April 2017 to 18 September 2018
For the 17 months starting April 2017, rainfall deficiencies are still present over large parts of New South Wales away from the northeast coast and southern border; eastern Victoria; central to southwestern Queensland; southern Northeast Pastoral and Murraylands districts of South Australia, and coastal areas of the Southwest Land Division in Western Australia.
Rainfall in the last week has had little effect on deficiencies.
Affected areas along the west coast of Western Australia have generally received between 50% and 70% of average. Rainfall in affected areas of Queensland, New South Wales and South Australia has generally been between 20% and 60% of average for the period.
Product code: IDCKGRWAR0