Yes, it's been raining a lot, but that doesn't mean Australia's drought has broken
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Yes, it's been raining a lot, but that doesn't
mean Australia's drought has broken
25 August 2020, by Lynette Bettio, Shannon Symons
unfortunately drought areas have expanded.
Three years with little rain
The Bureau of Meteorology is not responsible for
declaring whether a region is or isn't in
drought—that's a state government responsibility.
But we do analyze rainfall and water data, which
indicate whether a region is recovering.
In the three years from January 2017 to the end of
2019, rainfall for much of Australia was greatly
reduced—with both 2018 and 2019 especially dry.
Rainfall deficiencies were most severe in the
northern Murray–Darling Basin; the period was the
driest and hottest on record for the basin as a
Rainfall deciles from January 2017 to December 2019
showing the depth of longer-term rainfall deficiencies whole.
over large areas. Credit: BOM
These record warm temperatures exacerbated dry
conditions, at times rapidly drying soils in only a
matter of months. This led to periods in 2017 and
Heavy rain in parts of Australia in recent months 2019 that researchers have termed "flash drought."
has raised hopes Australia's protracted drought is
finally over. But determining whether a region has
recovered from drought is a complex undertaking.
For example, a drought-stricken area may get
enough rain that farmers can plant a viable crop,
but that same rain may not affect major water
storages. We've seen that in southern
Queensland, where water restrictions remain in
place despite recent rain.
And from a social, economic and environmental
perspective, one great season of rain does not
usually make up for a run of bad seasons.
So today, in World Water Week, we consider the
effect of this year's rain. The upshot is that most Rainfall deciles from January 1, 2020 to July 31, 2020,
drought-ravaged areas still need sustained, above- showing the impact of recent rainfall across Australia.
average rain before streamflow and water storage Credit: BOM
levels return to average. And in other parts of
Australia where little rain has fallen in 2020,
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2020: partial recovery in the east This increase in soil moisture is a very positive
foundation—catchments are now primed to produce
Since January this year, above-average rainfall has runoff and inflows to water storages if there is
fallen on some parts of eastern Australia, significant rainfall in spring.
particularly across some of the worst drought-
affected areas of central and western New South But soil moisture levels are below average for
Wales and southwest Queensland. In February, August across much of southwestern Australia,
much of eastern NSW experienced heavy rain, southern parts of South Australia, northern
while there were more widespread and consistent Tasmania, northern parts of the Northern Territory
falls through many parts of southeastern Australia and parts of central Queensland.
from February to April.
Not all dams have filled up
But some areas have largely missed out on recent
rains. Southern South Australia and southwest In Sydney, water storage levels had been declining
Western Australia have received below-average since July 2016. This resulted in level 2 water
rainfall in 2020, continuing the dry conditions of restrictions introduced in December 2019 and
2019. Drought areas in parts of the southern coast Sydney's desalination plant operating at full
of Western Australia and southwestern South capacity. But heavy rain in February and August
Australia have expanded this year, and the regions this year filled Warragamba Dam to capacity,
may face a difficult spring and summer. further increasing Sydney's storage levels.
Wetter soils, better crops In contrast to Sydney, major storage levels in the
northern Murray–Darling Basin remain low, at only
Eastern Australia's recent rain has helped replenish 21% of total capacity despite rainfall in recent
soil moisture levels, enabling favorable crop and months. Unlike the significant and rapid recovery of
pasture growth in many areas. For August to date, these storages in 2010 and 2016, the current rate
soil moisture is above average across eastern of recovery is slow. Significant follow-up rain is
coastal areas and mostly average to above needed to replenish these northern basin water
average in Murray–Darling Basin catchments. storages.
In the west, while Perth's water supply system
relies on desalinated water and groundwater to
supplement its storages, the dry conditions are
reflected in the Harvey rural supply system south of
Perth. It needs a further 100,000 megalitres to
replenish the drawdown of the past two years.
Total storage as at 18 August 2020 (% of total capacity)
compared to the last ten years for Sydney storages.
Credit: BOM
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Total storage as at 31 July (% of total capacity) Total storage as at July 31 (% of total capacity)
compared to the last ten years for the northern compared to the last ten years for the Harvey system.
Murray–Darling Basin. Credit: BOM Credit: BOM
So is the drought over? The bureau will provide further updates on current
rainfall deficiencies through regular reports such as
For many regions in eastern Australia, rainfall in its monthly Drought Statement and weekly rainfall
2020 has eased drought conditions by wetting soils tracker.
and helping fill dams on farms. But most drought-
affected areas still need sustained above average The bureau's Drought Knowledge Center provides
rainfall for streamflow and water storages to information about drought in your area. Water
increase to at least average levels. Reporting Summaries for the Murray–Darling Basin
provide an overview of water currently in storage
Recently the Bureau of Meteorology raised its El and commitments made for this water to different
Niño–Southern Oscillation (ENSO) status to La users, including the environment. The Water
Niña ALERT. This means there is three times the Storage Dashboard tracks water storages levels
normal likelihood of a La Niña weather pattern in across Australia.
2020. La Niña events typically result in wetter than
average conditions over Australia in winter and This article is republished from The Conversation
spring. under a Creative Commons license. Read the
original article.
Separately, warmer conditions in the eastern Indian
Ocean may also boost the chance of a wetter end
to the year. Provided by The Conversation
The bureau's latest outlook indicates the eastern
two-thirds of Australia is very likely to receive above
average rainfall in coming months. However,
southwest Western Australia is less likely to have
above average rainfall.
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APA citation: Yes, it's been raining a lot, but that doesn't mean Australia's drought has broken (2020,
August 25) retrieved 19 June 2022 from https://phys.org/news/2020-08-lot-doesnt-australia-drought-
broken.html
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