Drought
Rainfall deficiencies and water availability

Rainfall deficiencies continue despite some January rain

It was the driest and warmest year on record for Australia in 2019.The annual summary shows a year of prolonged dry conditions, especially across eastern and southern Australia. Above average rainfall across some areas in January 2020 was not sufficient to clear rainfall deficiencies at annual and longer timescales.

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 also 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 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 February to March, issued 30 January indicates the likelihood of a wetter or drier than average February to April are roughly equal for much of Australia. However, parts of northern Western Australia and the northern Murray-Darling Basin are slightly more likely to be drier than average. The breakdown of the positive Indian Ocean Dipole is one of the reasons below-average rainfall is not so likely as it has been over recent months. The IOD typically wanes with the start of the northern monsoon. It should be noted, however, that southern states are currently in their climatologically drier time of the year, which typically brings a seasonal drop in water storages.

6-month rainfall deficiencies

Rainfall deficiencies at the 6-month timescale, from August 2019 to January 2020, have decreased across much of northern Australia following January's rainfall. Tropical systems brought above average rainfall to much of inland northern and northwestern Queensland, and across much of Western Australia away from the eastern Kimberley and the west coast.

Nevertheless, serious to severe rainfall deficiencies persist across many parts of Australia. Deficiencies affect much of New South Wales and southeastern Queensland, extending into Queensland's Central Coast region inland of Townsville; across parts of Queensland's Cape York Peninsula; the northeastern Top End and inland northern parts of the Northern Territory, and pockets of the eastern half of the Kimberley; across much of Western Australia's south coast and South West Land Division; much of South Australia away from the southeast and the northwest to central pastoral areas, extending into parts of the southern Northern Territory; northern Victoria and East Gippsland; and northern Tasmania.

22-month rainfall deficiencies

Rainfall deficiencies for the period from April 2018 to January 2020 continue generally similar to those for the 21 months ending December 2019, but have decreased in severity across parts of the northern half of Western Australia and in the Northern Territory, and in southern Victoria following above average January rainfall.

Serious to severe rainfall deficiencies are in place for the 22-month period from April 2018 to January 2020 across much of the Kimberley and South West Land Division in Western Australia, and parts of the central and southwestern Pilbara, northeastern Gascoyne, and northeastern Interior District; much of the Northern Territory except areas along 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 much of northern and eastern Tasmania.

Much of the eastern half of New South Wales away from the coast, especially the northeast, has had record low rainfall for the 22-month period, as has much of greater southeastern Queensland, areas of western New South Wales and eastern South Australia, some central areas of the Northern Territory, the southeast of the South West Land Division and parts of the south coastal region 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 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 36 months from February 2017 to January 2020 has been the driest on record for any 36-month period starting in February when averaged over the Murray–Darling Basin and New South Wales. Average rainfall for the Murray–Darling Basin was 916.7 mm over the last 36 months, which is more than 100 mm lower than the second-driest (1027.3 mm from February 1900 to January 1903), whilst New South Wales received around 140 mm less rainfall than the next driest period, the 36 months from February 1900 to January 1903. 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−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. January saw average to above average rainfall in parts of NSW, but this was not widespread enough to impact on long-term rainfall deficiencies.

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

Very dry soils across the Murray–Darling Basin in January soaked up much of the rain resulting in limited or no runoff and inflows to the major storages.

The storages in the northern Murray–Darling Basin remain extremely low, having received only minor inflows. Collectively, the major storages of the northern Basin are now at 6.0% of capacity, an increase of 0.3% from last month. This very minor increase represents the first increase in storage levels in the Northern basin since July 2017.

Many individual storages remain extremely low, including Keepit and Split Rock in the Namoi valley at 1 % and 0.9% respectively, Coolmunda in the Border Rivers valley at 1.6% and Burrendong in the Macquarie valley at 1.6%. Beardmore and Leslie in the Condamine-Culgoa valley both increased this month by up to 5% reaching 7.8% and 5.8% respectively.

Further down the Darling river system, three of the four Menindee Lakes remain empty. Many towns in the Basin, including Dubbo, Orange, Bathurst are under water restrictions 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 dropped again in January to 38%. Hume, Lake Eildon and Dartmouth, the three largest storages in the Basin, dropped by up to 6% reaching 19%, 48% and 38% of capacity respectively by the end of January. 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.

The heatwaves and bushfires have both put pressure on the water resources of the southern Murray–Darling Basin in January. Several of the catchments of the major storages of the southern Murray–Darling Basin have been affected by bushfires. The major storages affected include Lake Hume where 60% of the catchment has been burnt and the upper Murrumbidgee storages on the Tumut River where more than 90% of several of the storage catchments have been burnt. The Tumut River storages including Blowering and Talbingo reservoirs, serve as both water supply and hydro-electric storages. Bushfires can cause both short-term water quality issues and long-term water supply issues with reduced catchment runoff yields over a 5-20 year period.

Continued low streamflows in the Murray–Darling Basin

Despite rain during January, streamflow remains below average across most of the Murray–Darling Basin. There have been slight increases in the flow in the Gwydir and Border Rivers tributaries in the north, but flow remains very much below average throughout most of the major river systems in the northern Basin.

January is traditionally a period of higher runoff in many of the northern catchments, with summer rainfall becoming more dominant the further north you go. In this context the runoff and resulting streamflow have been very much below average so far this summer filling season and many of the rivers are still without flow.

The River Murray system in the southern Basin maintained near average flow primarily due to continued bulk water releases from the storages with minimal runoff reaching the major rivers in January.

Urban water storages

The accessible storage volume decreased in all the major urban storage systems in Australia except Darwin which remained stable in January. The Hobart system showed the largest proportional decline followed by Canberra, Adelaide, Perth and Sydney.

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

The exceptionally dry soils in the catchments of the Sydney water storages absorbed the near average rainfall that Sydney received in January. While the rainfall did replenish the soil moisture by up to 15%, the catchments remain very dry and there has been minimal runoff into the storages As a result, Sydney water storage levels continued to fall by 1.3% to 42.2% despite the desalination plant operating at full capacity and the implementation of Level 2 water restrictions in December.

The impact of the recent bushfires that burnt over 35% of the catchment of Warragamba Dam, is still being assessed. The storage levels in Warragamba Dam, Sydney's largest water storage, have been declining since July 2016 reaching 43% at the end of January. The reduction in vegetation through bushfires can result in a short-term increase in runoff and potentially inflows to the storage. This can, however, be complicated by risks to water quality through the washing of ash and debris into the dam.

Late monsoon yet to replenish Darwin water storage

The late onset of the 2020 monsoon (just declared on the 2nd of February 2020) in Darwin has resulted in continued decreases in Darwin water storage levels . Darwin River Dam, the principal water supply for Darwin, typically fills to 100% during the monsoon dropping to about 70% at the end of the northern dry season. However, the 2019 monsoon rains were very much below average and the storage only increased to 79%. It has since decreased a further 25% to 54% of accessible storage capacity, the lowest it has been since December 2009.

Soil moisture

January soil moisture in the root zone (the top 100 cm) has decreased over parts of parts of inland and western New South Wales, compared to December.

Soil moisture for January was below to very much below average for much of New South Wales, particularly along the coast and extending into northeast Victoria and East Gippsland; large areas across eastern Queensland and Cape York Peninsula; much of Tasmania; parts of eastern and northern South Australia; across the South West Land Division in Western Australia; and large parts of the Top End and central to southeastern Alice Springs District in the Northern Territory.

Conversely, above average January rainfall over much of Western Australia, western to central South Australia, and much of northern inland Queensland and the adjacent east of the Northern Territory has resulted in a marked increase in soil moisture. Above average rainfall in much of central and southern Victoria has also increased soil moisture compared to last month.

Despite good rainfall during January over large areas, at the 12-month timescale soil moisture for February 2019–January 2020 was very much below average over very large areas of Australia.

Minor increases in soil moisture in the northern Murray–Darling Basin

The rootzone soil moisture increased marginally across most of the Murray–Darling Basin during January. After a dry December, the soils in the major water yielding catchments in the northern Basin saw increases of more than 15% in soil available water content following rain in January. The rain replenished the soil moisture to average levels across some areas but still much of NSW remains very much below average.

None of the Murray–Darling Basin catchments registered the lowest on record soil moisture this month, compared to four in December, but some smaller areas of in NSW and SA are still seeing lowest soil moisture on record.

Despite some increases in soil moisture during January, the catchment average soil moisture over the past 37 months (January 2017 to January 2020), since the dry period began, remains the lowest on record in 12 of the 26 river catchments in the Murray–Darling Basin. Soil moisture levels for the past 37 months have been lowest on record for the Namoi, Gwydir, Moonie, Border Rivers, Castlereagh, Macquarie–Bogan, Darling, and Condamine–Culgoa catchments in the northern Basin and the Lake George, Lachlan, Lower Murray and Murrumbidgee catchments in the southern Basin.

• January rainfall slightly above average for Australia as a whole, mostly due to above average falls in parts of western and central Queensland and inland Western Australia
• Rainfall below average for parts of New South Wales and the west coast of Western Australia, and pockets of far northern Australia
• Rainfall deficiencies persist across many parts of Australia, but have decreased across some areas of northern Australia
• Soil moisture increased in the northern Murray–Darling Basin but remains below average through central New South Wales
• Inflows remain limited for major water storages in the Murray–Darling Basin
• Storage volumes decreased in all major urban systems