South West of Western Australia
Reduced rainfall in the South West of Western Australia has resulted in flows to public water supply dams decreasing by more than 50% since the mid - 1970s.
The most severe projections by CSIRO are for average annual rainfalls to decline in the South West by 20% by 2030 and 60% by 2070, from the standard period used to forecast streamflows. This is based on a high emissions scenario. However, it is worth noting that CSIRO climate change modelling suggests that some rainfall activity will be more intense and this may increase flood risk.
Research conducted by the Indian Ocean Climate Initiative (IOCI) has found that in the South West:
- average temperatures have increased by 0.8 degrees Celsius since 1910 with most change occurring over the past 50 years;
- average Indian Ocean surface temperatures have increased by 0.6 degrees Celsius;
- over the past 35 years, the number of storms have decreased, bringing less rain; and
- over this same period, annual rainfalls have decreased by up to 10% and winter rainfalls have decreased by up to 15%.
The Department of Water is currently using the IOCI data to determine sub-regional climate scenarios for the Perth-Peel Regional Water Plan.
