Drought
Rainfall deficiencies and water availability

February rain eases rainfall deficiencies in some areas

Above average rainfall across some areas in January and February 2020 was not sufficient to clear rainfall deficiencies at annual and longer timescales. 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.

Rainfall deficiencies 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. 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 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 March to May, issued 27 February, indicates an increased chance of wetter than average conditions across some areas of southern Australia in autumn. However, parts of northern Western Australia and scattered parts of the tropical north have a slightly increased chance of being drier than average. The breakdown of the positive Indian Ocean Dipole at the start of the year and the persistence of neutral conditions in the Pacific is one of the reasons below-average rainfall is not so likely as it was during spring and summer. 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.

7-month rainfall deficiencies

Rainfall deficiencies at the 7-month timescale, from August 2019 to February 2020, have decreased across much of eastern and western Australia, and parts of the Top End, following rainfall during February. Tropical cyclone Esther contributed to above average rainfall between the Gulf of Carpentaria and the Kimberley, a slow-moving surface trough and the remnants of tropical cyclone Uesi contributed to above average falls across much of eastern Australia, tropical cyclone Damien contributed to above average rain to much of the west of Western Australia, and above average rainfall in eastern South Australia was also aided by tropical moisture.

Despite this rain, serious to severe rainfall deficiencies persist across large areas of Australia. Deficiencies remain in large areas of New South Wales in central and southern regions inland of the ranges and across the western third of the State; extending into far southwestern Queensland, eastern and northern South Australia, and the southwest of the Northern Territory; along the South Australia–Western Australia border and parts of southern South Australia; pockets of south coast and west coast Western Australia; a large area in the central to notheastern Top End in the Northern Territory; and Tasmania's Central North and Midlands.

23-month rainfall deficiencies

Rainfall deficiencies for the period from April 2018 to February 2020 have eased slightly across most of Australia, compared to those for the 22 months ending January 2019. 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, and it will take several more significant rainfall events to turn around those long-term deficiencies.

Serious to severe rainfall deficiencies are in place for the 23-month period across much of the Kimberley and South West Land Division in Western Australia, the northeastern Interior District, and parts of the western Pilbara; much of the Northern Territory except areas of the east; 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.

While the area of lowest on record rainfall for the period has reduced compared to last month, areas of record low rainfall for the 23-month period persist in much of western New South Wales and adjacent eastern South Australia, areas along the New South Wales–Queensland border, 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.

February rainfall eased the severity of long-term deficiencies on the eastern coastal regions of Australia but 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 March 2017 to February 2020 has been the driest such period on record. Average rainfall for the Murray–Darling Basin was 974 mm over the last 36 months, the only sub−1000 mm total in 120 years of record and around 50 mm lower than the second-driest (1023 mm from March 1900 to February 1903), whilst New South Wales also received around 50 mm less rainfall than the next driest period, the 36 months from March 1900 to February 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 some water storages in the northern Murray–Darling Basin

Water storage levels increased in most of the major storages in the northern Murray-Darling Basin during February, but they decreased through the south, resulting in the total storage holding steady at 31% of capacity for the Basin.

Following the wetting of the landscape in January, the rainfall in February did result in some runoff into storages in the northern Murray–Darling Basin but total storage in the northern Basin remains at only 12.6%. The current level in the north is similar to the storage levels in 2008, towards the end of the Millennium drought.

Several of the smaller water storages in the far northern Basin reached capacity in February including Chinchilla Weir on the Condamine River, and Jack Taylor Weir and Lake Kajarabie (Beardmore) on the Balonne River. The catchments of these rivers received some of the highest rainfall in the Murray–Darling Basin during the month, resulting in flooding in the area.

In the east, Coolmunda increased from only 1% to 33% full at the end of February and Leslie and Glenlyon increased by more than 10% to 15% and 14% respectively. The other major storages of the northern Murray–Darling Basin increased by less than 5% accessible storage.

The total storage in the southern Basin dropped another 1.5% this month. Minor increases were seen in the storages at the headwaters of the Lachlan and Murrumbidgee river valleys but otherwise decreases of up to 15% were seen right across the southern storages. 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.

Rivers running in the northern Murray–Darling

The rain during February has resulted in rivers in the northern Murray–Darling Basin flowing for the first time since 2017. All of the major river systems of the northern Murray–Darling Basin have had some flow during February. The largest flows were seen at St George on the Balonne River where 1200 gigalitres was observed. This water has been making its way down the Condamine-Balonne-Culgoa river system during February and is expected to join the Barwon flows in early March.

The Namoi, Gwydir, and Border Rivers have also followed up the minor flows seen in January with more substantial and continuous flows in February. These rivers feed the Darling River which was flowing as far down as Louth in northwestern New South Wales by the end of February. This flow is expected to reach Menindee Lakes in mid-March. The recent flows in the northern rivers have resulted in many streamflow stations going from below average in January to very much above average in February.

Most of the rivers in the southern Basin remain below average to lowest on record since 1980 but all major rivers remain flowing. Flow in the Lachlan River, that runs through central New South Wales, has seen a further decrease this month despite rain in its upper catchments.

Urban water storages

Sydney water storages almost double in ten days

A slow-moving trough that delivered 400 mm of rain to Sydney in one week produced enough runoff to almost double the amount of water stored in the Sydney storages in February. The accessible water in the Sydney storages increased from 42% on 8 February to 81% on 18 February. Warragamba, the largest storage in the system, increased by 800 GL, almost enough water to fill the Sydney Harbour twice over. The speed and volume of runoff was likely to have increased due to the lack of vegetation following 35% of the catchment being burnt by bushfires this season.

Sydney water storages have been declining since July 2016 and Level 2 water restrictions were introduced in December 2019 to reduce pressure on supply. Water restrictions have now been lowered to Level 1 as of 1 March 2020.

Late monsoon stars to replenish Darwin groundwater but not surface water storage

Despite the onset of the monsoon, Darwin water storage levels have not had the significant increases typical of the wet season. 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 since decreased to 54% at the end of January and during February only increased to 55%.

Normally, the water storages would be full or have finished filling by the end of February. The water storages peaked by the end of February in 8 of the past 12 wet seasons, but have been known to continue filling as late as April.

Groundwater systems, which are heavily relied upon by agriculture in the area, have had some recharge even though the rain has not yet replenished the surface water stores. There are two major groundwater resources in the Darwin Rural Area, Howard East and Berry Springs, both of which rely on wet season rainfall to replenish each year. Currently, the water level at Berry Springs has increased by 6 metres to be within 10 m or less of the surface. However, the water levels are now above what was seen after the 2018–19 wet season.

Soil moisture

February soil moisture in the root-zone (the top 100 cm) has increased over much of Australia, compared to January.

Soil moisture for February was below to very much below average along the western border and northwest of New South Wales, far southwestern Queensland, and parts of northeastern South Australia; parts of southwest and southeast Western Australia, a coastal area of the northwestern Gascoyne and southeastern Pilbara, and a large area of the western Kimberley; parts of the Top End, particularly inland regions; pockets of northeast Victoria and East Gippsland; and much of eastern Tasmania.

Conversely, soil moisture was above average for most of the eastern half of South Australia away from the northeast; much of Victoria away from the northern Mallee, northeast, and East Gippsland; much of central to coastal New South Wales, except parts of the southwest slopes; a broad area extending through Queensland from the southeast and central southern areas, through the Central West, to the Gulf Country; across much of the Northern Territory away from the Top End; and through large areas of Western Australia, particularly through central regions, from the central Pilbara coast through the eastern Gascoyne, extending to the region between Perth and Geraldton, and into the southern Goldfields.

Despite a wet February over large areas of eastern and western Australia, and above average rainfall in some areas for January, the influence of very low rainfall in the preceding months of 2019 is still evident in the 12-month soil moisture for March 2019–February 2020. Soil moisture at the 12-month timescale was very much below average over very large areas of Australia.

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

The root-zone soil moisture in February was average or above average across most of the Murray–Darling Basin. None of the Murray–Darling Basin catchments registered the lowest on record soil moisture this month, the first time since November 2018.

There were significant increases in soil moisture across large areas of the northern Murray–Darling Basin. In the northeastern Basin this built on increases seen earlier in 2020, taking soil moisture from near zero in mid-January to over 50% by the end of February. There were decreases seen in the southeast of the Basin where the relatively wet soils following rain at the end of January progressively dried out to be near average by the end of February.

Importantly, there have been increases in soil moisture in the major water yielding catchments along the western side of the Great Dividing Range. This means that any rain that does fall is now more likely to result in runoff.

The soils in western New South Wales are still very dry; this is not unusual for this time of year, but does continue a long period of below average soil moisture levels. The 38-month (January 2017 to February 2020) average soil moisture remains at lowest on record across almost half of the Basin and will likely remain low without several months of above average rainfall. Despite the recent rain, the catchment average soil moisture for this 38-month dry period remains lowest on record in 13 of the 26 river catchments in the Murray–Darling Basin.

This long period of dry means that while there may now be surface soil moisture for grass to grow, vegetation and dryland crops have not yet had an extended period of moisture to recover and grow.

• February rainfall was slightly above average for Australia as a whole, with heavy falls across parts of the east coast and north
• Rainfall was below average for pockets of northern Australia, much of the western Kimberley, far southwestern Queensland and northwestern New South Wales, and a large area of southeast Western Australia and western South Australia
• At the shorter timescale—since August 2019—rainfall deficiencies have decreased through eastern New South Wales, southeastern to inland southern Queensland, and the South West Land Division in Western Australia
• The accumulated rainfall deficit at the longer timescale—since April 2018—means recent rainfall has resulted in less significant reduction of deficiencies
• Soil moisture has increased across much of eastern Australia and the South West Land Division in Western Australia, but has decreased in other parts of Western Australia, and remains below average through northwestern New South Wales
• Water storage levels in the northern Murray–Darling Basin remain low despite significant inflows to some storages; inflows remain limited in the south of the Basin
• Sydney water storages almost doubled in ten days