Serious or Severe Drought: Probability of at least one (serious or severe)
in a yr - 28.9%, at least one in 5 years - 81.8%, at least
one in 10 yrs - 96.7%.
Moderate or Serious or Severe Drought: Probability of at least one
(moderate or serious or severe) in a yr-45.1%, at least one
in 5 years - 95.0%, at least one in 10 yrs - 99.7%.
Droughts Overall: Probability of at least one (severe,
serious, moderate or slight) in a year - 54.5%, Return Period -
1.8
years, Range - 2 to 27 season (average 8.5 seasons) or 4 to
29 months (average 10.5 months).
If there is a drought -
20.9% chance it is severe, 22.4% chance it is serious (43.6%
severe or serious), 32.8% chance it is moderate and 23.9%
it is slight.
Longest period between any drought is 29
seasons (31 months); longest period between a severe or
serious drought is 128 seasons (10 years and 10 months).
Drought in general means water shortage and rainfall
deficiency.
Meteorological (climatological) drought
is defined in terms of the magnitude of a precipitation
shortfall/deficit and the duration of this shortfall event.
This is assessed by first
examining the rainfall periods of three months or more for
selected places to see whether they lie below the 30th
percentile (lowest 30% of the historical records). The
approach used to determine the rainfall deficit is an
adjusted version of the decile method developed by Gibbs and
Maher (1967). An adjusted version of this method is used as
the measurement of droughts within the Australian Drought
Watch System.
The drought levels, based on
consecutive three-month historical data, are defined as
follow:
**• Slight:**
rainfall ranges from less than 30^{th} percentile to
the 20^{th} percentile
**• Moderate:**
rainfall ranges from less than the 20^{th}
percentile to the 10^{th} percentile
**• Serious:**
rainfall ranges from less than the 10^{th}
percentile to the 5^{th} percentile
**• Severe:**
rainfall less than the 5^{th} percentile
The level of a
drought period/episode (drought lasting three or more
months) is described based on the maximum consecutive three-month rainfall deficit.See
our
Drought and Precipitation Statement for the latest
including how droughts are accessed. |