Rainfall deficiencies and water availability
Australia's climate in 2019
Periods of extreme heat bookend Australia's warmest and driest year on record.
A wet April in the southeast helps ease rainfall deficiencies in some areas
Rainfall during April 2020 has been above average across much of the southeast, and for Victoria it was the third-wettest April on record. However, the size of the rainfall deficit accumulated over annual and longer timescales prior to 2020 is very large over much of Australia. This means recent above average rainfall has not yet made up for this shortfall, and serious or severe rainfall deficiencies persists over very large areas at these longer timescales.
Additional widespread, above average rainfall is still needed to lift areas out of deficiency at annual and longer timescales and provide relief from the impacts of this long period of low rainfall (such as renewing water storages).
The Bureau of Meteorology also monitors rainfall deficiencies and impacts on water resources on longer timescales such as the current severe multi-year drought affecting large parts of eastern Australia. This is discussed further below, and we have Special Climate Statements on this long dry period.
The role of climate change in rainfall reduction over southern Australia is discussed in State of the Climate 2018 which shows that parts of southwest Australia, and large parts of southeast and eastern Australia including parts of southeast Queensland and southern and eastern New South Wales, have seen substantial declines in cool season rainfall in recent decades.
The Climate Outlook for May to July, issued 30 April, indicates an increased chance of wetter than average conditions for most of Australia. The north and east coast have roughly equal chances of wetter or drier conditions.
9-month rainfall deficiencies
Rainfall deficiencies at the 9-month timescale, from August 2019 to April 2020, have decreased across most affected areas of Australia following above average rainfall across large areas during March and April. The progress of ex-tropical cyclone Esther in early March contributed to above average rainfall in an arc from the inland Kimberley in the northwest to the southeast of Australia in March, whilst above average rainfall from vigorous cold fronts across the southeast in April further eased deficiencies in parts of the region. If deficiencies ease further in May this period will be no longer be formally monitored within the Drought Statement although rainfall decile and deficiency maps will continue to be produced for standard periods.
Serious to severe rainfall deficiencies still persist in several parts of the country: in small areas along the border of South Australia and New South Wales, in northwest South Australia and the southwest of the Northern Territory; a small region spanning far eastern Victoria into southeastern New South Wales; parts of the south coast, southwest and west coast of Western Australia; an area in the central to northeastern Top End in the Northern Territory and parts of the far northern Kimberley; and areas of eastern Queensland, including the inland southeast.
25-month rainfall deficiencies
Rainfall deficiencies for the period from April 2018 to April 2020 have eased slightly in severity and extent across most of Australia, especially across southeastern parts of New South Wales, compared to those for the 24 months ending March 2020. However, the depth of the rainfall anomalies over this period is very great, in excess of 400 mm below average for the period over large areas of the east and north. It will take several further significant rainfall events to turn around those long-term deficiencies.
Serious to severe rainfall deficiencies are in place for the 25-month period across much of the South West Land Division in Western Australia, parts of the Kimberley and the northeastern Interior District, and parts of the western Pilbara; large areas of the Northern Territory away from the east; much of South Australia; the southeastern quarter of Queensland; most of far western and northeastern New South Wales and much of the southeast of that State; across northwest Victoria and the far-east of that State.
While the area of lowest on record rainfall for the period has again reduced month-on-month, areas of record low rainfall for the 25-month period persist along the border of New South Wales and South Australia, in areas along the New South Wales–Queensland border, in parts of the southern coast of the South West Land Division and South Coastal District in Western Australia, and scattered pockets elsewhere.
Extended dry conditions over eastern Australia
Rainfall deficiencies have affected most of the New South Wales, Queensland and South Australian parts of the Murray–Darling Basin since early 2017, as detailed in the last update on the long-running dry and for 2019 in the Annual Climate Statement. These longer-term deficiencies also extended to parts of the New South Wales coast, particularly in the Hunter and Illawarra to southeastern districts, and to much of the eastern half of South Australia from Adelaide northwards. The deficiencies were most extreme in the northern Murray–Darling Basin, especially in the northern half of New South Wales and adjacent southern Queensland, where areas of lowest on record rainfall extended across large areas. Some of the largest rainfall deficiencies occurred in the upper catchments of some of the major tributaries of the Darling, including the Macquarie, the Namoi–Peel, and the Border Rivers.
A wetter start to 2020 has eased the severity of short-term deficiencies over much of eastern Australia and has provided a better start to the winter cropping season in many regions. However, the rainfall deficiencies were severe over an extended period so recovery will be a slow process. The impact on water resources is still evident, especially in northern parts of the Murray–Darling Basin. Significant deficiencies remaining at long-term timescales across many parts of the country. Averaged over the Murray–Darling Basin and New South Wales, the 36 months from May 2017 to April 2020 has been the second-driest such period on record, behind May 1900 to April 1903, spanning the Federation Drought. Other areas affected by longer-term rainfall deficiencies include eastern Victoria, eastern and northern Tasmania, eastern South Australia except for the southeast, and some parts of southwest Western Australia.
The dry conditions of the last three years were particularly acute during the cool season, which is important in many regions for generating runoff. April−October rainfall totalled across the three years was the lowest on record across large parts of western and eastern New South Wales. All three years had seasonal rainfall below 200 mm for New South Wales, with 2018 and 2019 both below 150 mm; there is no previous instance of two consecutive years below 150 mm, or three consecutive years below 200 mm. The very much below average November and December rainfall in 2019 over most of the main water catchments of New South Wales and the Murray–Darling Basin as a whole has further exacerbated the effect of low inflows to date. Rainfall in the first four months of 2020 rainfall has improved flows in parts of the Basin but total storages are still low, especially in the northern Basin (see Water section of this Statement).
Water storage levels remain low in the Murray–Darling Basin
Water storage levels increased slightly in most of the major storages in the Murray–Darling Basin, taking the total storage to 35%, an increase of 3% since last month and 1.5% since the same time last year.
The total storage in the northern Basin increased by 3.4% in April and is now 5.8% higher than the same time last year. Increases in April were primarily driven by inflows to Burrendong and Windamere storages in the Macquarie Valley. Current levels in the Northern Basin remain at only 17% of capacity, less than 2% higher than the storage levels in 2009, at the height of the Millennium drought in the north. Many of the northern basin catchments have experienced prolonged dry conditions on multi-year timescales and significant follow-up rainfall is still needed to replenish water storages.
The total storage in the southern Basin increased by 3.4% to 40.5% of capacity. Some of the smaller storages in the southern catchments including Lake William–Hovell increased by up to 30% but the minor increases in the larger storages such as Lake Victoria, Eppalock, Blowering, and the Menindee Lakes drove the total storage increase in April.
Bulk downriver releases ceased in April and inflows increased with higher than average rain in the upper catchments of the Murray River. This resulted in the levels in the very large storages of Hume, Dartmouth, and Eildon showing slight increases.
Water in the Lower Darling River reaches the Murray River
The river flows generated in February and March in the northern Murray–Darling Basin rivers have continued to make their way down the Darling River system during April.
The flow in the Darling River at Bourke is above average for April, compared to the past 40 years, and is still flowing into the Menindee Lakes. The water released from the Menindee Lakes into the Lower Darling River in late March joined the Murray River water near Wentworth on the 12th of April. This is the first significant flow in the Lower Darling River since January 2018 and an important event for local communities.
Following the limited April rain and the drying of the soil, the catchments in the far northern Basin have started to dry out and the ephemeral rivers that flow from them have started to recede. The upper reaches of the Condamine and Warrego rivers have stopped flowing. In contrast the Macquarie River is still delivering significant volumes of water into the Darling River system.
Despite recent rain in the southern Basin, flow in most of the rivers remain average to lowest on record since 1980. A significant proportion of the rain went to the increases seen in soil moisture in the catchments. Bulk water releases ceased in April and, while allocations were low this season, the delivery of water contributed to the flow recorded in the Murray River. The Murray River above Hume Dam did record very much above average flow for April, but the majority of this water will likely be retained in Lake Hume for future needs.
Urban water storages
Monsoon provides valuable recharge to groundwater around Darwin
The Darwin surface water storage levels increased slightly during April to 69.5% of capacity, which is still 6% lower than this time last year. This represents a 17% increase this wet season compared to only 5% in the 2018/19 wet season. With 1 May signalling the end of the northern Australia wet season, storages are unlikely to receive significant surface water inflows until next wet season. However, the groundwater systems have seen good recovery this season and will provide valuable baseflow to surface water systems and a supply of water for agriculture in the Darwin area.
The two major groundwater resources in the Darwin Rural Area, Howard East and Berry Springs, rely heavily on wet season rainfall to replenish each year. This wet season, the groundwater level at Berry Springs increased by 9 m to be within 13 m or less of the surface. The bores in Howard East and Berry Springs are not expected to increase further this year. The levels will decrease during the dry season from environmental flows and agricultural extraction.
Root-zone soil moisture (in the top 100 cm) increased through April over much of southeastern Australia, compared to March. After a drier than average April in the southwest, soil moisture has decreased there.
Soil moisture for April was above average over most of New South Wales; much of Victoria except the southwest and far east; the southern third of Queensland, extending north along the Capricornia Coast, and extending across the Channel Country; across parts of the Northern Territory and the inland Kimberley; and across most of Tasmania.
Soils were drier than average for the month in Western Australia across much of the South west Land Division and areas of the interior of that State, extending north to parts of the southern Kimberley and eastern Gascoyne; for areas of inland Queensland and for scattered smaller areas of far eastern Victoria, western Victoria and southeastern South Australia which have been affected by long-term rainfall deficiencies.
Despite the first four months of 2020 being wet over large areas of eastern and western Australia, and some areas of the eastern mainland having above average rainfall for the January to April period, the influence of very low rainfall over longer timescales is still evident in the 12-month soil moisture for May 2019–April 2020, which was very much below average over very large areas of Australia.
Valuable increases in soil moisture in New South Wales
The root-zone soil moisture in April was above average to very much above average across most of the Murray–Darling Basin.
There were valuable increases in soil moisture across central and southern areas of the Murray–Darling Basin. Notably some of the Riverina agricultural area, in southwest NSW increases of more 15% of available water content in April. The Murrumbidgee and Lachlan River catchments received significant rain this month increasing soil moisture in areas that have been dry since the start of 2017.
Importantly, there were also increases in soil moisture in the major water yielding catchments of the northern and, particularly, the southern Basin. The catchments of Hume, Dartmouth, and Eildon dams, the biggest water storages in the Murray-Darling Basin, had significant increases in soil moisture this month. This is a very positive foundation going into late autumn and the beginning of the southern water storage filling season. The wetter soils mean that any rain that does now fall is more likely to result in runoff into rivers and storages.
Soil moisture decreased through the far north of the Basin, but it remains above average following major increases in February and March.
- April rainfall above average across much of the southeast
- However, April rainfall below average for much of eastern Queensland, an area extending from the western Kimberley and southern and western parts of Western Australia
- At the shorter timescale—over the nine months since August 2019—rainfall deficiencies have decreased across most affected areas in the southern half of Australia
- Rainfall deficiencies have also decreased at longer timescales—such as the 25 months since April 2018—although the accumulated rainfall deficit is significant, and deficiencies over the longer period persist in many parts of Australia
- Soil moisture has increased across much of eastern and southwest Australia, and remains above average for large areas
- Water storage levels in the northern Murray–Darling Basin remain low despite some recent inflows
- Water in the Lower Darling River reaches the Murray River
Product code: IDCKGD0AR0
A very dry month for the southeastern mainland increases rainfall deficiencies
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?
Go to Bureau Blog: 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.
Australian Government drought assistance
Department of Agriculture and Water Resources information and contacts:
- Know your weather
Know your weather. Know your risk.
- Water Information
Water resources assessments and forecasts
- Water and the Land
Weather and climate for primary industries
- Australian Bureau of Agricultural and Resource Economics and Sciences
(ABARES) is a research bureau within the Department of Agriculture, Fisheries and Forestry aimed at Australia's primary industries.
- Climate Change in Australia
Bureau/CSIRO website, including rainfall and temperature projections and impacts for the coming decades.
- CSIRO-BoM Drought-EC Report (July 2008)
An assessment of the impact of climate change on the nature and frequency of exceptional climatic events, and accompanying Supplementary Information.
For the week to 26 May 2020, rainfall was recorded in every State and Territory away from the central interior of the continent.
At the start of the week, a high pressure system in the Tasman Sea extended a ridge along Queensland's east coast, providing moist onshore flow onto the north tropical Queensland coast. Moderate to locally heavy falls exceeding 250 mm around Mission Beach were reported. Bingil Bay recorded 301.8 mm on the 21st, a new daily rainfall record for May at that site.
A surface trough extended from the Gulf Country, down through inland Queensland to the southeast of New South Wales and, along with another surface trough close to the east coast, produced isolated thunderstorms with widespread light to moderate falls across central, southern, and southeastern Queensland and eastern New South Wales.
During the first half of the week, a broad cloudband over northern Australia, and produced light to moderate falls across much of the Kimberley, central districts of the Northern Territory and the base of the Top End, and the Cape York Peninsula in Queensland. A broad upper trough maintained areas of rain across central to northern parts of Queensland, with widespread moderate falls across the northern half of that State during the middle of the week before the trough dissipated.
Also at the start of the week, a complex frontal system moved across southeastern Australia, with moderate falls recorded over much of Victoria, southeastern South Australia, and Tasmania. The passage of this front was associated with severe storms in parts of Victoria. By the middle of the week, this system had developed a complex low off the central and southern New South Wales coast, with further light to moderate rainfall in eastern New South Wales and northeastern Victoria. Snowfall was recorded in the Alpine regions.
Towards the end of the week, a deep low pressure system developed off the southwest coast of Western Australia as ex -tropical cyclone Mangga interacted with a strong cold front. A pre-frontal trough moved through the west Pilbara and Gascoyne, while the cold front moved through the west coast, and an associated complex low tracked the southwest and south coast. Squally and damaging winds, and moderate to locally heavy rainfall, were reported over parts of Western Australia from the west Pilbara down to the southwest.
At the end of the week, showers, thunderstorms, and squally winds continued to affect southern parts of Western Australia. The trough in the north moved east and produced moderate to locally heavy falls in the west Kimberley and Northern Interior.
Rainfall totals in excess of 200 mm were recorded around Mission Beach and Tully in the north tropical coast of Queensland, including the highest weekly total of 516 mm at Bingil Bay.
Rainfall totals in excess of 100 mm were recorded in pockets of the west Kimberley in Western Australia; small areas of the Hunter District in New South Wales; and the north tropical coast of Queensland.
Rainfall totals in excess of 50 mm were recorded the western Pilbara, and coastal areas of the Gascoyne and pockets of southwest Western Australia; from the north tropical to central coast, and adjacent inland districts of Queensland; areas in the Hunter and Illawarra districts in New South Wales; and far East Gippsland in Victoria.
Rainfall totals between 10 mm and 50 mm were recorded in the Kimberley, Pilbara, Gascoyne, Interior, South West Land Division and south coast of Western Australia; the northern half of the Northern Territory away from the northern Top End; most of Queensland except the southwest; central to eastern New South Wales; most of Victoria; southern and parts of eastern South Australia, and northern and western Tasmania.
Impact of recent rainfall on deficits
Rainfall deficits over Australia for the 9-month (August 2019–April 2020) and 25-month (April 2018– April 2020) periods are discussed in the Drought Statement, issued on 7 May 2020.
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 9-month and 25-month periods, extended to the week ending 26 May 2020.
Rainfall for the period 1 August 2019 to 26 May 2020
Areas of serious to severe rainfall deficiencies for the period starting 1 August 2019 persist in areas along the border of South Australia and New South Wales, extending in parts of western New South Wales; in pockets of southern South Australia and across the far north of that State, extending into the southwest of the Northern Territory; in far eastern Victoria and some parts of southeastern New South Wales; pockets of southwest coast and west coast of Western Australia; a large area in the central to northeastern Top End in the Northern Territory and far northern Kimberley; and pockets of eastern Queensland, including the inland southeast.
Rainfall over the past week eased deficiencies along the Central West coast of Western Australia, and in small areas of the Central Highlands in Central Queensland.
Affected areas in far western New South Wales, far northern South Australia and the south of the Northern Territory have generally received less than 40% of average, while remaining areas have received less than 60% of their average rainfall.
Rainfall for the period 1 April 2018 to 26 May 2020
Serious to severe rainfall deficiencies are in place for the 25-month period across much of the South West Land Division in Western Australia, parts of the Kimberley and the northeastern Interior District, and parts of the western Pilbara; much of the Northern Territory except areas of the east; much of South Australia; the southeastern quarter of Queensland; most of New South Wales; across northern Victoria and most of the eastern half of that State except parts of West and South Gippsland; and along the coast of northern and eastern Tasmania.
Areas of record low rainfall for the 25-month period persist in western New South Wales and adjacent eastern South Australia, areas along the New South Wales–Queensland border, parts of the southern coast of the South West Land Division and South Coastal District in Western Australia, and scattered pockets elsewhere.
The rain that fell in the past week had little impact on deficiencies at this time scale.
Affected areas through the interior of Australia into western New South Wales, southern inland Queensland, northeastern South Australia and the southern parts of the Northern Territory have generally received less than 50% of average rainfall for this period. Remaining areas have generally received between 80% and 50% of average rainfall.
Product code: IDCKGRWAR0