WATER deficiencies persist in much of the south-western half of Western Australia, despite above average August rainfall through much of the interior of Australia.
Root-zone soil moisture has increased across large areas of the country, but remains below average in parts of the southern coast and south-west Australia.
According to the Bureau of Meteorology's (BoM), latest Drought Statement, released on Tuesday, rainfall during August 2020 was very much above average through parts of the interior of the continent, including the south coast of WA.
This resulted in a reduction of rainfall deficiencies at shorter timescales (for example the five months to August 2020), although there has been little change at longer multi-year timescales.
"Heavy rain between Albany and Esperance in south coastal Western Australia has removed short-term deficiencies along the coastal strip but had little impact on longer-term deficiencies," the BoM statement said.
"Serious or severe rainfall deficiencies for the five-month period April-August 2020 are in place in Western Australia across most of the south-western half of the State, excluding parts of the Gascoyne, south coast and Central West District."
Persistent, widespread, above average rainfall is needed to lift areas out of deficiency at annual and longer timescales and provide relief from the impacts of this long period of low rainfall.
According to the statement, coastal rain contributed to significant increases in soil moisture on the coast, but most of South West Western Australia remained dry in August.
"Small areas around Albany moved from lowest on record in July to very much above average in August," it said.
"However, root-zone soil moisture across most of the Wheatbelt remained below average this month.
"Despite monthly fluctuations and localised rain events, the region has been experiencing dry soil conditions since April 2018."
The root-zone soil moisture deciles for the 29-month period to August 2020 show a significant portion of the South West Coast drainage division has experienced record-low soil moisture over this period.
The rain in August in South West Western Australia fell on very dry soils and did not fall far enough inland to produce significant runoff and inflows to the major water storages in the region.
"The total storage in the 21 major water storages in the South West Coast drainage division is at 43.6 per cent of capacity, an increase of only 2.5pc in August," the statement said.
"The largest increase resulted from rain on the south coast where the small storage of Quickup increased by 37pc to 80pc of capacity.
"However, the larger storages of Wellington and Serpentine only increased by 4pc and 1.6pc respectively."
