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 following driest November on record
It was Australia's driest November and spring on record. November rainfall was below to very much below average across most of Australia, including much of northern and eastern Queensland, eastern New South Wales, South Australia, Western Australia, and the Northern Territory.
For the year to date (January–November), rainfall has been below to very much below average over much of Australia. For Australia as a whole, it was the second-driest January–November on record, behind January–November 1902. Daytime temperatures have also been very warm, second highest on record for mean maximum temperature, adding to moisture stress. A recent climate update on the year-to-date and likely end-of-year scenarios is available.
Widespread rain and scattered thunderstorms associated with a slow-moving trough and cold front in the first days of November brought rainfall across some areas of eastern Australia. Through some areas of inland Queensland and central to western New South Wales this event has brought the first significant rainfall since early May. During this event Bourke had its wettest November day on record. This rain cleared short-term (4 month) deficiencies in the area around Bourke, but long-term deficiencies remain.
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 December to March, issued 28 November, indicates a drier than average end of the year is likely for most of Australia. The chance of exceeding median rainfall for December is less than 35% over much of eastern Australia. The lower odds of receiving average or above average rainfall is likely being influenced by the positive Indian Ocean Dipole. The IOD typically wanes with the start of the northern monsoon, however, given the current positive IOD is so strong, it is likely to take several weeks to decline, and could persist well into mid-summer. It should also be noted that southern states are moving into their drier time of the year, which typically brings a seasonal drop in water storages over summer months.
4-month rainfall deficiencies
A record-dry November for Australia has continued rainfall deficiencies at shorter timescales.
Rainfall for the 4 months from August to November 2019 has been record low over much of northeastern New South Wales. Areas of short-term rainfall deficiency in the central north of the State have been cleared following above average rainfall in this region in November. Serious to severe rainfall deficiencies extend across eastern and southern New South Wales inland of the ranges; across northern Victoria and East Gippsland; across much of southern Queensland and large parts of the north of that State; northern Tasmania; South Australia; southern parts of Western Australia ; and large parts of the Northern Territory.
11-month rainfall deficiencies
Areas of rainfall deficiencies for the year to date remain very similar to those present at the end of October with some increase in severity and extent in the Northern Territory and northern parts of Western Australia. Around 60% of Australia is in decile 1 (lowest 10% on record) for the period.
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. Areas of serious to locally severe deficiencies also exist across the southern 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, 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 North West Slopes and Plains in New South Wales and the Southern Downs in Queensland, rainfall for January–November 2019 is more than 30% below previous record lows.
Serious to severe rainfall deficiencies 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; the Mallee and parts of eastern Victoria; and coastal parts of northeastern Tasmania. In Western Australia serious to severe rainfall deficiencies affect most of the interior of that State, nearly all areas along the south coast and most of the Southwest Land Division, and parts of the Pilbara and Kimberley. A large area has observed lowest on record rainfall for January–November, particularly in the central Northern Territory, and around the Alice Springs District, pastoral South Australia, and central eastern Western Australia.
20-month rainfall deficiencies
Rainfall deficiencies for the period April 2018 to November 2019 remain generally similar to those for the period April 2018 to October 2019 but have increased somewhat in severity in the Northern Territory.
Serious to severe rainfall deficiencies are in place for the 20-month period from April 2018 to November 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 much of the Top End and 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 near Tasmania's east and north coasts.
Much of the northeast inland of New South Wales has had record low rainfall for the 20-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 and scattered pockets elsewhere.
Extended dry conditions over eastern Australia
Rainfall deficiencies have affected most of 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 parts of northeastern New South Wales inland of the Great Dividing Range to as far west as Dubbo and Walgett, as well as smaller areas on central and northwestern New South Wales and southern Queensland. 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 35-month periods commencing in January, the 35 months from January 2017 to November 2019 has been the driest on record averaged over the Murray–Darling Basin (36% below the 1961–1990 average), and for the state of New South Wales (also 36% below average). New South Wales received over 100 mm less rainfall than the next driest period, ending November 1902 during the Federation Drought. Other areas affected by longer-term rainfall deficiencies include eastern Victoria, eastern and northern Tasmania 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
The dry soils absorbed most of the rain that fell across the Murray–Darling Basin during November, resulting in limited runoff and very low 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 6.3% of capacity, a decline of 0.3% from last month. Some of the lowest major storages are Keepit and Split Rock in the Namoi valley at 0.8% and 1.1% respectively, Burrendong in the Macquarie valley at 3.1% and Copeton in the Gwydir valley at 6.9%. Further down the Darling river system, three of the four Menindee Lakes are empty. Many towns in the region, including Dubbo, have raised their water restriction levels again this month and are investigating alternative water sources, such as groundwater, to augment their water supply.
The volume of water in storage in the southern Murray–Darling Basin also dropped again in November. This follows the start of irrigation seasons in August and reduced inflows to the major storages due to dry catchments and limited rain. The Hume dam, the third largest storage in the Basin, has dropped over 5% to 33% 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 on average the period when the bulk of downriver releases occur, and inflows are lower.
Continued low streamflows in the northern Murray–Darling Basin
Streamflows have been average to lowest on record during November right across the Murray–Darling Basin. Very few of the northern Basin rivers are flowing at all and while this is not unusual for some of the northwestern rivers, the rivers in the northeast are seeing lowest on record flows for this time of year. There are minor flows still running through some of the rivers downstream of the storages in the Namoi, Macquarie, Gwydir and Border Rivers, largely due to minor releases from the storages but this water is not making it to the lower sections of these rivers or into the Darling River.
The rain that fell in northwest NSW in early Novermber did deliver some local flows to the Warrego and Darling rivers near Bourke. These flows made it downstream as far as Tilpa but most sections of the rivers have now ceased to flow (see Water Data Online).
The streamflow in the southern Murray–Darling Basin ranges from average to very much below average, with the exception of the lower Darling River. The Darling river at Menindee recorded lowest on record with no flow at all in November.
Streamflow is influenced by both water released from major storages and consumptive take from the rivers, in addition to natural runoff from rainfall. There have been some increases in soil moisture in the northern Basin but it is clear that very little of the rain is running off the landscape and into the rivers and storages. Until significant rain occurs the rivers and storages will continue to decline through water use.
Urban water storages
The amount of water in all the major urban storage systems decreased in November except for Melbourne and Hobart which saw minor increases. The decreases were all approximately 2% with Brisbane dropping below 60% for the first time since 2009.
Sydney's major water storage levels continue to fall prompting another increase in water restrictions
Lower than average rainfall combined with very dry soils has resulted in very low runoff from large areas of the Sydney water storage catchments. The great Sydney area received lower than average rainfall with very much below average seen in the southern 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 45.8% of capacity, a decline of 1.7%, during November prompting an announcement from Sydney Water of a planned increase in water restriction to Level 2 on the 10th of December.
Sydney storage catchments are exceptionally dry with average soil moisture at the 2nd lowest on record for November and 5th lowest on record for any month since 1911. 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.
November soil moisture in the root zone (from 0 to 100 cm deep) deciles were similar to those for October over much of Australia. Rainfall at the start of the month in western New South Wales has eased deficiencies there. Soil moisture for November was below average for eastern New South Wales; eastern Queensland; northeast Victoria; northeast Tasmania; much of South Australia; most of western and southern Western Australia, and pockets of the Kimberley; and much of theNorthern Territory.
The relatively dry soils seen during November extends the run of dry months this year. Soil moisture for January–November 2019 was very much below average over very large areas of Australia.
Soil moisture increase through the central Murray–Darling Basin
The rain in early November slightly eased the dry soil moisture conditions in large parts of the Murray–Darling Basin. None of the Murray–Darling Basin catchments registered lowest on record soil moisture this month, compared to six catchments in October.
The rain was centred around Bourke but conditions eased slightly throughout the central and western Basin. The soils are still extremely dry along the east coast of NSW but the proportion of the state experiencing very much below average soil moisture in November reduced to 25% compared to 72% in October.
Soils remain very dry in the northeast of the Basin and down along the western side of the Great Dividing Range where the majority of the inflows to the Darling River system originate.
The catchments in the southern Basin that received near average rainfall during late autumn to early winter continue to dry out. In the upper reaches of the major water yielding catchments of the Goulbourn and Ovens rivers the available soil water content has dropped by up to another 10% and remains below average.
Despite some increases in soil moisture during November, long-term records in low soil moisture continue to be set. The catchment average soil moisture over the past 35 months (January 2017 to November 2019) remains the lowest on record in ten of the 26 river catchments in the Murray–Darling Basin.
- November rainfall lowest on record for Australia
- Rainfall deficiencies continue in many areas, with some increases across northern Australia
- Long-term rainfall deficiencies, record-low for some periods, continue to severely limit water resources across the Murray–Darling Basin
- Inflows remain limited to major water storages in the Murray–Darling Basin
- Slight increases in soil moisture in the central Murray–Darling Basin
- Sydney water storage levels continue to fall prompting increase in water restrictions
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