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.
Rainfall deficiencies continue, increase in some areas
September rainfall was below to very much below average across nearly all of New South Wales except parts of the coast; most of Queensland except parts of the southwest, Gulf Coast, and northern Peninsula; most of Victoria except areas in the southwest and large parts of Gippsland; most of Tasmania, except parts of the east coast; the northern half of the Northern Territory; the southern half of Western Australia; and large areas of South Australia in the west, north, and east of that State.
For the year to date (January–September), rainfall has been below to very much below average over much of Australia, as is reflected in the 9-month rainfall deficiencies. For Australia as a whole, it was the fourth-driest January–September on record and the driest since 1965. It was the driest January–September on record for South Australia, and amongst the ten driest on record for New South Wales, Western Australia, and the Northern Territory.
Whilst the Bureau of Meteorology's monthly Drought Statement focuses on rainfall deficiencies for periods up to two years duration, we monitor 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-term period.
The role of climate change in rainfall reduction over southern Australia is discussed in State of the Climate 2018. Parts of southwest Australia, and large parts of southeast and eastern Australia, including New South Wales and southern Queensland, have seen substantial declines in cool season rainfall in recent decades.
The Climate Outlook for October to December, issued 3 October, indicates a drier than average end of the year is likely for most of Australia. The chance of exceeding median rainfall for October to December is less than 30% over most of the mainland, except the north to northwest of Western Australia. This outlook suggests that near-term improvement in rainfall deficiencies is unlikely.
9-month rainfall deficiencies
Rainfall deficiencies for the year to date have increased in northeastern New South Wales and southeastern Queensland, pastoral areas of South Australia, and across the South West Land Division and south coast in Western Australia.
In New South Wales, serious to severe rainfall deficiencies extend across most of the North West Slopes and Northern Tablelands, along with coastal areas from the Hunter northwards. Scattered pockets of deficiencies also exist between the New South Wales Tablelands and Northern Country District and central Gippsland coast in Victoria. In Queensland, serious to severe rainfall deficiencies affect the greater southeast, the eastern Maranoa, and the Capricornia District. Areas of record low rainfall cover an area extending from the Southern Downs in Queensland to the New South Wales' central Northern Tablelands, Northwest Plains, and part of the Mid-North Coast district. In some areas, particularly in the Northern Tablelands and Southern Downs, rainfall for January–September 2019 is more than 20% below previous record lows.
Modest rainfall in the northwest of the Alice Springs District in the Northern Territory has lessened the severity of rainfall deficiencies in parts of the region, but was insufficient to clear deficiencies.
Serious to severe rainfall deficiencies are also evident across much of the central and southern Northern Territory away from the Queensland border; most of the pastoral districts of South Australia, extending into western New South Wales and the northern Mallee in Victoria, and parts of agricultural districts of South Australia on the Eyre and Yorke peninsulas and around the Adelaide region and Kangaroo Island. In Western Australia serious to severe rainfall deficiencies affect most of the interior of that State, large parts of the south coast, much of the Southwest Land Division, and parts of the Pilbara and Kimberley. A large area has observed lowest on record rainfall for January–September, particularly in the Northern Territory, northern South Australia, and central eastern Western Australia, as well as scattered pockets of southeast Western Australia and southwest South Australia.
Deficiencies persist in eastern Tasmania, but have decreased somewhat in parts of the east coast. Despite September's rain, January to September 2019 rainfall has been the ninth-lowest on record for the East Coast District.
18-month rainfall deficiencies
Rainfall deficiencies for the period April 2018 to September 2019 have generally increased across southern Queensland, from eastern South Australia through western New South Wales, central New South Wales west of the ranges, eastern and northeastern Victoria, and across the South West Land Division in Western Australia when compared to the period April 2018 to August 2019. Elsewhere, rainfall deficiencies in affected areas generally continue.
Serious to severe rainfall deficiencies are in place for the 18-month period from April 2018 to September 2019 across much of the northern half of Western Australia, except parts of the inland Kimberley, the central and southwestern Pilbara, and northeastern Gascoyne; across much of the South West Land Division in Western Australia; much of the Northern Territory away from the Top End and eastern border; most of central and eastern South Australia, except the southeastern tip; most of southern and southeastern Queensland, extending across much of the Central Highlands and Capricornia districts; much of New South Wales, except some pockets of the central coast, far southeast, and inland west; northwestern Victoria and along the Murray in the Northern Country District, extending through the parts of the Northeast, Central, and East and West Gippsland districts; and in parts of Tasmania's east and north coast.
Much of the northeast inland of New South Wales has had record low rainfall, as have parts of adjacent southern Queensland, areas of western New South Wales to eastern South Australia, much of the Southeast Coastal District in Western Australia, and other smaller areas scattered 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 the start of 2017. These longer-term deficiencies extend to parts of the New South Wales coast, particularly in the Hunter and Illawarra districts, and to much of the eastern half of South Australia from Adelaide northwards. The deficiencies have been 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 extend from the Great Dividing Range west as far as Dubbo and Walgett. Some of the largest rainfall deficiencies have occurred in the upper catchments of some of the major tributaries of the Darling, including the Macquarie, the Namoi–Peel, the Gwydir, and the Border Rivers.
When compared to other 33-month periods commencing in January, the 33 months from January 2017 to September 2019 has been the driest on record averaged over the Murray–Darling Basin (34% below the 1961–1990 average), as well as over the northern Murray–Darling Basin (40% below average) and for the state of New South Wales (34% below average). All three regions have also been the driest on record for the 21 months from January 2018 to September 2019, whilst the 27 months from July 2017 to September 2019 rank second in all three regions; only the 1900–02 peak of the Federation Drought has been drier. The last 33 and 21 months have also been the driest on record averaged over the Border Rivers, Macquarie–Bogan, Namoi, Gwydir, and Castlereagh catchments, with the last 21 months also the driest on record for the Moonie, Condamine–Culgoa, and Lower Murray catchments.
Another area of longer-term rainfall deficiencies affects Gippsland, in eastern Victoria, and the east coast of Tasmania. Both the West Gippsland and East Gippsland districts have had their driest 33 months on record. Rainfall for the period commencing January 2017 has been lowest on record for much of Gippsland, extending roughly from east of around Sale to around Point Hicks. Rainfall deficits in 2019 in this region have mostly been less extreme than in 2017 and 2018, but have still been sufficient to reinforce deficiencies at multi-year timescales.
The dry conditions of the last three years have been particularly acute during the cool season, which is important in many regions for generating runoff. Rainfall for the period from April to September was less than 50% of average in all three years in 12 of the 30 rainfall districts of New South Wales. The Central Western Plains (North), which encompasses Nyngan, Trangie, Gilgandra and Coonamble, has had less than one-third of its average cool-season rainfall in all three years.
Limited inflows for major water storages in the Murray–Darling Basin
The dry soils again absorbed most of the little rain that did fall across the Murray–Darling Basin during September, resulting in limited runoff and inflows to the major storages.
The storages in the northern Murray–Darling Basin remain extremely low, having received no significant inflows. Collectively, the major storages of the northern Basin are now at 8% of capacity, a decline of 0.5% from last month and down from 27% at the same time last year. Some towns in the region have raised their water restriction levels and are investigating alternative water sources, such as groundwater, to augment their water supply.Filling of storages in the southern Murray–Darling Basin has slowed compared to August, with an increase of 0.6% last month bringing the total storage volume to 50% of capacity at the end of September, down 12% compared to the same time last year. The large storages, including Dartmouth, Hume, and Eildon, all remain above 40%, bringing the total storage of the Murray–Darling Basin to 41% at the end of September, unchanged since the previous month.
Record low streamflows in the northern Murray–Darling Basin
Another month of dry conditions has resulted in the lowest streamflows on record for 15 gauging stations in the northern Murray–Darling Basin. Streamflow observations span the period 1980 to present. The rivers with record low flows largely correspond to the catchments that also had record low soil moisture levels for the past 33 months, including Border Rivers, Gwydir, Namoi, Castlereagh, Macquarie–Bogan, and Condamine–Culgoa catchments.
Lowest streamflows on record were also seen in the lower Darling River in the southern Murray–Darling Basin. Aside from the Darling River, the record low streamflows observed in the north did not occur in the southern Basin. All streamflows were average to very much below average, with the exception of Mitta Mitta River in the southeast of the Basin.
Urban water storages
Higher than average rainfall fails to replenish Sydney's major water storages
Sydney water storage levels continued to fall despite the desalination plant operating at full capacity and the implementation of Level 1 water restrictions in June. Whilst areas close to the coast in the Greater Sydney area and northwards received higher than average rainfall in September, most storages are located in areas south and west of Sydney that only received average rainfall for the month.
Rainfall in mid-September provided a brief reprieve in the storage's downwards trend but by the month's end Sydney's storages had declined to 49% of capacity. This equates to a drop of 0.6% from the previous month and 14% since the same time last year, continuing the consistent downwards trend in storage levels since June 2017.
September soil moisture deciles in the root zone (from 0 to 100 cm deep) remain similar to those for August. Soil moisture for September was below average for most of New South Wales; most of southern Queensland and much of the Peninsula and Gulf Country regions; most of eastern, northeastern and far northwestern Victoria; most of South Australia except some pockets along the coast and in the central west of the State; most of Western Australia except the eastern interior; most of the Northern Territory except for the central interior; and much of Tasmania.
The relatively dry soils seen during September extends the run of dry months this year. Soil moisture for January–September 2019 was very much below average over very large areas of Australia.
Dry soils persist in the Murray–Darling Basin
Soil moisture remains very low across most of the Murray–Darling Basin. In several of the southern catchments the effect of average rainfall during late autumn to early winter in several of the southern catchments continues to be seen in near-average soil moisture levels for September.
The changes in actual soil moisture this month have again been largely driven by moisture availability, with the wetter soils in the south drying more significantly than the already dry soils further north.
Despite slight increases in soil moisture in some catchments, the northern catchments of the Namoi, Gwydir, Moonie, Border and Macquarie–Bogan Rivers all had their lowest September soil moisture levels on record.
Another dry month over the Murray–Darling Basin has set new long-term records for soil moisture for the past 33 months (January 2017 to September 2019) in ten of its 26 river catchments. Soil mositure levels for the past 33 months have been lowest on record for the Namoi, Gwydir, Moonie, Border Rivers, Castlereagh, Macquarie–Bogan, and Condamine–Culgoa catchments in the northern Basin and the Lake George, Lachlan, and Murrumbidgee catchments in the southern Basin.
- September rainfall was below to very much below average for most of Australia
- Rainfall deficiencies have continued, with moderate increases in some areas
- Long-term rainfall deficiencies, record-low for some periods, continue to severely limit water resources across the Murray–Darling Basin
- Root-zone soil moisture was below average for September for most of Australia
- Water storages in the northern Murray–Darling Basin extremely low, with no significant inflows during September
- Above average September rainfall in Sydney failed to replenish its major water storages
Product code: IDCKGD0AR0