Drought
Rainfall deficiencies and water availability

Rainfall deficiencies persist across large parts of Australia

August rainfall was below to very much below average across nearly all of New South Wales, extending into much of southern and western Queensland, northern and far eastern Victoria, and nearly all of South Australia. Rainfall for the month was also below average for the southern half of the Northern Territory, however, much of northern and Central Australia typically receives very little rainfall at this time of year.

For the year to date (January–August), rainfall has been below to very much below average over much of Australia, as is reflected in the 8-month rainfall deficiencies. It has been the fifth-driest start to the year on record for Australia as a whole, and over the southern half of Australia it was the driest January–August on record for the region (January to August 1940 is the second-driest, closely followed by 1902 as third-driest).

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 drought, the drought and its impact on water resources and a July webinar where we explore this current drought more deeply. We will continue to monitor this situation.

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 have seen substantial declines in cool season rainfall in recent decades.

The Climate Outlook for October to December, issued 5 September, 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 40% over most of the mainland, except the north and west of Western Australia. This outlook suggests that near-term improvement in rainfall deficiencies is unlikely.

8-month rainfall deficiencies

Rainfall deficiencies for the year to date have increased in northeastern New South Wales and southeastern Queensland, and pastoral areas of South Australia following below average rainfall for the month. Deficiencies have increased in parts of the north of the South West Land Division in Western Australia, while decreasing slightly in parts of the southwest and south coast.

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. 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 central Northern Tablelands and Northwest Plains districts in New South Wales into the Southern Downs in Queensland; the size of the areas experiencing record low rainfall has increased compared to that for January–July rainfall, and now includes area a small area on the Mid-North Coast including Port Macquarie and Taree. In some areas, particularly in the Northern Tablelands and Southern Downs, rainfall for January–August 2019 is more than 20% below previous record lows.

Serious to severe rainfall deficiencies are also evident across most of the western half of the central and southern Northern Territory; most of the pastoral districts of South Australia (extending to far western border areas of New South Wales and the northern Mallee in Victoria), and parts of the Eyre and Yorke Peninsulas, the Adelaide region, and Kangaroo Island; most of the interior of Western Australia, large parts of the south coast, much of the Southwest Land Division, and parts of the Pilbara and Kimberley. A large area of Central Australia has observed lowest on record rainfall for January–August, particularly in the Northern Territory, as well as scattered pockets of southeast Western Australia and southwest South Australia.

Serious to severe rainfall deficiencies also exist across eastern Tasmania. Rainfall for the January to August period has been the second-lowest on record for the East Coast District.

17-month rainfall deficiencies

Rainfall deficiencies for the period April 2018 to August 2019 have generally increased across New South Wales, southern Queensland, eastern and northern Victoria, and South Australia compared to the similar period ending July 2019. Elsewhere, rainfall deficiencies in affected areas generally continue with little change.

Serious to severe rainfall deficiencies are in place for the 17-month period from April 2018 to August 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 coast.

Much of the northeast inland of New South Wales has had record low rainfall, as have parts of adjacent southern Queensland, and smaller areas in other states.

Extended drought 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, 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, and the Border Rivers.

When compared to other 32-month periods commencing in January, the 32 months from January 2017 to August 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 20 months from January 2018 to August 2019, whilst the 26 months from July 2017 to August 2019 rank second in all three regions; only the 1900–02 peak of the Federation Drought has been drier. The last 32 and 20 months have also been the driest on record averaged over the Border Rivers, Macquarie–Bogan, Namoi, Gwydir, and Castlereagh catchments, with the last 20 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 32 months on record, with a substantial area of record low rainfall in central Gippsland centred on Sale and Bairnsdale.

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 both 2017 and 2018 in 14 of the 30 rainfall districts of New South Wales. In 13 of these 14 districts, rainfall from April–August 2019 was also less than 50% of average. 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.

A limited winter filling season for major water storages in the Murray–Darling Basin

The dry soils have absorbed most of the rain that has fallen across the Murray–Darling Basin resulting in limited runoff and inflows to the major storages.

The winter "filling" season in the Southern Basin has been below average for the third year in a row while water storages of the Northern Murray–Darling Basin are extremely low or close to empty with no meaningful inflows. The major storages of the Northern Basin have now dropped well below those seen at the end of the Millennium Drought in 2010.

The large storages of the Southern Basin, including Dartmouth, Hume, and Eildon, all remain above 43% which brings the total storage of the Basin to 41% at the end of August, up only 2.8% from last month.

Note: MDB-South boundary has been adjusted to include the Menindee Lakes with a resultant reduction in the capacity of MDB-North and a corresponding increase in levels compared to the July Drought Statement.

Urban Storages

Sydney storage levels continue to fall

The prolonged dry conditions are also impacting the capital cities. Sydney storage levels dropped below 50% in June, triggering Level one water restrictions. Volumes continued to fall throughout winter, reaching 49% capacity during August, down 16% on this time last year. Storage levels have fallen consistently since June 2017.

The winter runoff from Sydney water storage catchments was the second lowest on record due to very dry soils and limited rainfall. The Kurnell desalination plant was switched on in January 2019 and has been supplying water to Sydney's supply system for five months. In August it reached its capacity of 250 ML per day, approximately 15% of Sydney's drinking water needs.

Darwin water storages not replenished by wet season

Very much below average rain over the 2018–19 wet season has left Darwin water storages at 62.9% at the end of August, down 22% compared to this time last year. The storage levels are likely to continue to fall over the remaining months of the dry season. Low soil moisture and limited surface water reserves have also put significant pressure on groundwater sources that were not replenished by monsoonal rains in 2019.

Soil moisture

August root-zone soil moisture (from 0 to 100 cm deep) deciles remain similar to those for July. Soil moisture for August was below average for most of New South Wales and southern Queensland, extending into the Capricornia District; most of eastern and northeastern Victoria and far northwestern Victoria; most of South Australia away from the coastal southeast; most of Western Australia except the eastern interior; most of the Northern Territory; much of Queensland's Cape York Peninsula; and much of eastern, northern, and western Tasmania.

The relatively dry soils seen during August extends the run of dry months this year. Soil moisture for January–August 2019 was very much below average over very large areas of Australia.

The soil moisture maps have changed from Lower layer (10 to 100 cm) to Root-zone (0 to 100 cm) to better represent the accessible water in the soil profile. As this only represents the addition of the top 10 cm regional patterns remain consistent with the lower-layer maps displayed last month.

Dry soils persist in the Murray–Darling Basin

Soil moisture remains very low across most of the Murray–Darling Basin, but the effect of above average early winter rainfall continues to be seen in average and above average soil moisture for August in several of the southern catchments.

The changes in actual soil moisture this month have 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, the northern catchments of Border Rivers, Gwydir River, and Macquarie–Bogan Rivers have all reached lowest on record winter soil moisture levels. The dry winter also pushed the soil moisture in many of the catchments to new long-term lows with the past 32 months (January 2017 to August 2019) representing the driest on record for nine of the Murray–Darling River Catchments, ranked against other 32-month periods starting any month.

• August rainfall was below average over much of New South Wales, southern Queensland, northern and eastern Victoria, South Australia, and northern Tasmania
• Rainfall deficiencies generally persist with little change in affected 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 August for most of Australia
• Water storages in the Northern Murray–Darling Basin extremely low, with no meaningful inflows during August
• Below average winter filling season for water storages in the Southern Basin for the third year in a row