Drought
Rainfall deficiencies and water availability

Rainfall deficiencies expand following driest December on record

It was Australia's driest December and driest end of the year on record. For the last three months of the year rainfall was below to very much below average across most of Australia, including much of Queensland, especially in the southeast, much of New South Wales, Victoria, South Australia, eastern Tasmania, Western Australia away from the Pilbara and Gascoyne regions, and the Northern Territory.

Daytime temperatures have also been very warm adding to moisture stress, with December Australia's warmest month since national records began in 1910. The annual summary for 2019 will be released in the first half of January.

Rainfall anomalies at longer timescales are very deep due to the prolonged nature of the current dry period, with below average rainfall over most months over much of the country since early 2017. Consistent, widespread, above average rainfall over several months will be needed to lift areas out of deficiency and provide relief from the impacts of this long period of low rainfall (such as renewing water storages).

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 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 January to April, issued 2 January, indicates a drier than average start to the year is likely for eastern Australia with wetter than average conditions more likely over the central and western regions. The increased odds of receiving above average rainfall is likely being influenced by the breakdown of the positive Indian Ocean Dipole. The IOD typically wanes with the start of the northern monsoon. It should be noted, however, that southern states are moving into their drier time of the year, which typically brings a seasonal drop in water storages over summer months.

5-month rainfall deficiencies

A record-dry and hot December following a record-dry November for Australia has exacerbated rainfall deficiencies at shorter timescales. Areas of rainfall deficiency at the five-month timescale, including areas of lowest on record, affect much of northeastern New South Wales and southeastern Queensland, a large area in central Queensland inland of Townsville, northern parts of the Northern Territory and a large area in western South Australia. Serious to severe rainfall deficiencies extend across many parts of Australia including much of New South Wales; across northern Victoria and East Gippsland; across much of Queensland excluding the southwest and very northern parts; northern Tasmania; South Australia; southern and eastern parts of Western Australia; and large parts of the Northern Territory.

12-month rainfall deficiencies

Areas of rainfall deficiencies for the calendar year 2019 have increased in severity following a record-dry December. Around 68% of Australia has rainfall totals in decile 1 (lowest 10% on record) for the period, with around 24% of the country has had lowest on record rainfall for the period.

In New South Wales, severe rainfall deficiencies and areas of lowest on record rainfall extend across most of the North West Slopes and Northern Tablelands, along with coastal areas from the Hunter northwards. Areas of serious to locally severe deficiencies also exist across the South Coast of New South Wales, and between the New South Wales Tablelands and the Central District in Victoria, as well as in inland to coastal central Gippsland. In Queensland, severe to lowest on record rainfall deficiencies affect the greater southeast, with serious to severe deficiencies affecting the eastern Maranoa, and the Capricornia District. In some areas, particularly in the Northern Tablelands and North West Slopes and Plains in New South Wales and the Southern Downs in Queensland, rainfall for January–December 2019 is more than 30% below previous record lows.

Severe rainfall deficiencies and areas of lowest rainfall on record are also evident across much of central and southern parts of the Northern Territory away from the Queensland border; most of South Australia except parts of the southeast, western Eyre Peninsula, and far northeast; across western New South Wales; and central eastern Western Australia. Serious to severe deficiencies are evident in the Mallee and parts of eastern Victoria; eastern Tasmania; and in Western Australia over most of the central region, nearly all areas along the south coast and most of the Southwest Land Division, and parts of the Pilbara and Kimberley.

21-month rainfall deficiencies

Rainfall deficiencies for the period from April 2018 to December 2019 continue generally similar to those to November 2019, but have increased in severity in parts of New South Wales.

Serious to severe rainfall deficiencies are in place for the 21-month period from April 2018 to December 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 except parts of the eastern border; much of South Australia; southern and southeastern Queensland, extending across much of the Central Highlands and Capricornia districts; 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 eastern Tasmania.

Much of eastern New South Wales, especially the northeast, has had record low rainfall for the 21-month period, as have parts of adjacent southern Queensland, areas of western New South Wales to eastern South Australia, large parts of central areas of the Northern Territory into Western Australia, south coastal Western Australia, east Gippsland in Victoria, and scattered pockets elsewhere. For the 21-month period just over half of New South Wales has had lowest on record rainfall.

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 a recent update on the long-running dry. These longer-term deficiencies extend 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 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 across large areas. 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.

The three years from January 2017 to December 2019 has been the driest on record for any 36-month period starting in January when averaged over the Murray–Darling Basin and New South Wales. Average rainfall for the Murray–Darling Basin was 918.0 mm over the last 36 months, which is more than 100 mm lower than the second-driest (1037.5 mm from January 1965 to December 1967), whilst New South Wales received around 170 mm less rainfall than the next driest period, the 36 months from January 1900 to December 1902 during 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 have been particularly acute during the cool season, which is important in many regions for generating runoff. April−September rainfall totalled across the three years was the lowest on record across almost all New South Wales, apart from some coastal areas and parts of the far west, as well as in most of subtropical Queensland. All three years had seasonal rainfall below 125 mm for New South Wales; there is no previous instance of two consecutive years below 125 mm, or three consecutive years below 175 mm. The very much below average October and November 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.

Limited inflows to major water storages in the Murray–Darling Basin

Very low rainfall and dry soils across the Murray–Darling Basin in December resulted in limited or no 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 5.7% of capacity, a decline of 0.6% from last month. However, individual storages are extremely low, including Keepit and Split Rock in the Namoi valley at 0.7% and 0.9% respectively, Coolmunda in Border Rivers valley at 1.4%, Burrendong in the Macquarie valley at 2.1%, Beardmore and Leslie in the Condamine-Culgoa valley at 2.4% and 2.8% respectively.

Further down the Darling river system, three of the four Menindee Lakes are empty. Many towns in the Basin, including Dubbo, Orange, Bathurst are under water restriction and are investigating alternative water sources, such as groundwater, to augment their supply.

The volume of water in storage in the southern Murray–Darling Basin also dropped in December. This follows the start of the irrigation seasons in August and reduced inflows to the major storages due to dry catchments and limited rain. Wyangala – the main headwater storage in the Lachlan valley has dropped to 12%. Hume dam, the third largest storage in the Basin, has dropped by over 7% to 26% of capacity this month. It is expected that the total storage volume in the southern Murray–Darling Basin will continue to decrease until late April as this is the period when the bulk of downriver releases occur, and inflows are on average lower.

Continued low streamflows in the Murray–Darling Basin

As a consequence of the very low rainfalls, streamflows in the Murray–Darling Basin during December were lower than average in most catchments. In the northern Basin very few of the northern rivers are flowing at all, although this is not unusual for some of the northwestern rivers for December. The rivers in the northeast; Condamine-Culgoa, Border Rivers, Gwydir, Namoi, Castlereagh and Macquarie saw very much below average to lowest on record flows for this time of year. In the southern Murray–Darling Basin streamflows were below average to very much below average in most catchments.

Urban water storages

The accessible storage volume decreased in all the major urban storage systems in Australia in December. The Adelaide system showed the largest proportional decline followed by Canberra, Hobart and Brisbane. The smallest decline was in the Melbourne system.

Sydney water storage levels continue to fall with Level 2 water restrictions in place

Very much below average rainfall was recorded in about 96% of the Sydney catchment area. This combined with very dry soils has resulted in very low runoff from large areas of the Sydney water storage catchments. As a result, 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. Accessible storage levels fell to 43.9% of capacity, a decline of 1.9%, during December prompting the announcement of Level 2 water restrictions on the 10th of December. The restrictions apply to all residents and businesses in Sydney, the Blue Mountains and the Illawarra.

Sydney storage catchments are exceptionally dry with average soil moisture at the lowest on record for December. Eight of the eleven Sydney storage catchments registered lowest on record soil moisture this month. The storage levels in Warragamba Dam, Sydney's largest water storage, have been declining since July 2016. Some rain has fallen during this time, but the soil has soaked up a significant proportion of the water and releases have continued to be made to supply Sydney. With the current exceptionally low soil moisture in the catchments, significant rain will be required to generate increases in soil moisture to the point of producing runoff and inflows to these storages. December rainfall was the lowest on record for the month in the Warragamba catchment.

Soil moisture

December soil moisture in the root zone (from 0 to 100 cm deep) has declined since November over much of Australia. Western New South Wales in particular has dried out since rainfall in this region in November. Soil moisture for December was very much below average for eastern New South Wales; eastern and northern Queensland; eastern Victoria; northeast Tasmania; parts of South Australia; most of southern Western Australia, and pockets of the Kimberley; and large parts of the Northern Territory.

Soils continue to be extremely dry along the east coast of New South Wales and the fraction of the State experiencing very much below average soil moisture in December has increased to 48% compared to 25% in November.

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

Dry soil conditions continued in the Murray–Darling Basin through December

Soil moisture remained very dry across most of the Murray–Darling Basin during December and was on average the second lowest on record for this month.

Four of the Murray–Darling Basin catchments registered lowest on record soil moisture in December, compared to none in November. Soil moisture was second-lowest on record for another five catchments.

Soils remain very dry in the eastern part of the Basin and along the Great Dividing Range where most of the inflows to the Darling River system originate.

Rain in early November slightly improved the dry soil moisture conditions in the central and western Basin but the soil moisture decreased by up to 15% during December. In the northern catchments of Gwydir, Namoi, Macquarie, Barwon-Darling, Paroo and Warrego the soil moisture dropped by between 5 and 15% during December.

In the upper reaches of the major water yielding catchments of the Goulburn, Upper–Murray, Ovens and Loddon rivers the available water content has dropped by up to another 10% and sits below to very much below average, similar to that of November.

Despite some increases in soil moisture during November, the catchment average soil moisture over the past 36 months (January 2017 to December 2019) remains the lowest on record in ten of the 26 river catchments in the Murray–Darling Basin. Soil moisture levels for the past 36 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.

• December rainfall lowest on record for Australia
• Rainfall deficiencies expanded and intensified in many areas following below average rainfall across much of Australia, especially in the east
• Long-term rainfall deficiencies, record-low for some periods, continue to severely limit water resources across the Murray–Darling Basin
• Inflows remain limited for major water storages in the Murray–Darling Basin
• Dry soil conditions continued across much of Australia through December
• Storage volumes decreased in all major urban systems