Projections currently indicate a potential drop in South Eastern Australian rainfall of as much as 50% by 2100. The coastal fringe down as far south as Sydney is not expected to be as badly impacted. However, the winter rainfall is expected to reduce in favour of the summer (summer rainfall up 50% by 2100). There is a question as to whether dams such as Mangrove Creek Dam and Warragamba will get less rain due to being behind the escarpment.
It is now apparent that when rain falls it will be more intense (e.g. Feb 2019 Townsville flooding). A warmer atmosphere can hold a lot more moisture. Hence, dry weather will evaporate more moisture from the ground than before and wet weather will create heavier downpours. East Coast Lows are likely to be more intense with stronger winds and higher rainfall.
Impact type 2050 2100 2300
. Low High Low High Low High
Average +2% -10% +15% -20%
Winter +2% -10% +10% -30%
Summer +2% -10% +20% -15%
These numbers do not reflect individual events such as storms. Rainfall in a month may not change much but if it falls on 1 day instead of 3 days, the risk of flooding is greatly increased.
[Reviewed Feb 2019]