Melbourne: Climate and water
- Total annual rainfall during the 2021-22 year was above average for the third consecutive year.
- Streamflows during the 2021-22 year were above average for the third consecutive year, reflecting the relatively wet conditions over the region.
- Soil moisture in the root zone (0–1 m depth) was predominantly average during the 2021-22 year.
For further information on the region's climate and water conditions during the 2021-22 year scroll down this page or click on the links below:
About the region
- The Melbourne region has a temperate climate and generally experiences mild winters and warm summers. Rainfall is relatively uniform throughout the year, but generally higher during the winter and spring months (June–November).
- Typically, streamflow in the region's rivers reflects the distribution of rainfall throughout the year. Higher streamflows and storage inflows occur during June–November; less streamflow occurs during the summer months (December–February).
Climate conditions
Rainfall
Figure C1 Annual and monthly rainfall deciles for the Melbourne region during the 2021-22 year
- Total area-averaged rainfall for the 2021-22 year was 867 mm, slightly more than the mean value of 861 mm.
- Rainfall was predominantly average across the region, with the western half experiencing above-average rainfall during the 2021-22 year.
- Above-average rainfall throughout spring (September-November 2021) was due to a weak negative Indian Ocean Dipole. It was the wettest October since 2011.
- Despite a La Nina event being declared in November 2021 and strengthening over summer, rainfall was predominantly below average in December 2021, and very much below average in February 2022.
- Rainfall was above average in March and April, but below average across almost the entire region in May.
- During June, rainfall was above average in the east, and average to below average across the west.
Figure C2 Total monthly rainfall for the Melbourne region during the 2021-22 year compared with the average and percentiles for the region
- Rainfall was above the 90th percentile in October 2021, with the region recording its wettest October since 2011.
- February 2022 was extremely dry, with rainfall below the 10th percentile.
- All other months ranked between the 10th and 90th percentiles.
Actual evapotranspiration
Figure C3 Annual and monthly actual evapotranspiration deciles for the Melbourne region during the 2021-22 year
- Total area-averaged actual evapotranspiration was average to above average across most of the region during the 2021-22 year.
- Evapotranspiration was predominantly above average across the region from July to November 2021 because of persistent rainfall; a result of a weak Indian Ocean Dipole and La Nina-like conditions in the Pacific Ocean.
- From December 2021 to June 2022, evapotranspiration varied from month-to-month, which reflected the rainfall the region received during each month. The exception was April, where evapotraspiration was predominantly below average, with some areas experiencing very much below average evapotranspiration, despite the average to above average rainfall.
- By June 2022, evapotranspiration was predominantly average to above average after the majority of the region received average to above average rainfall.
Soil moisture
Figure C4 Annual and monthly soil moisture deciles for the Melbourne region during the 2021-22 year
- Soil moisture in the root zone (0–1 m depth) was predominanty average during the 2021-22 year, with pockets of below average soil moisture in the east and areas of above average soil moisture in the west.
- During the first three months (July to September 2021), soil moisture was predominantly average, with areas of above average and below average soil moisture scattered across the region.
- Following above average rainfall throughout October and November, soil moisture was predominantly above average, with small areas being very much above average. However, after below average to very much below average rainfall across the region during December, soil moisture returned to average to below average.
- Despite predominantly above average rainfall in January, soil moisture continued to be average to below average, with some areas experiencing very much below average soil moisture.
- From February to May, soil moisture was average to very much below average in the east and average to above average in the west; a reflection of the rainfall distribution across the region during those months.
- By June 2022, soil moisture was predominantly average following above average rainfall in the east and average to below average rainfall in the west.
- More information on soil moisture distribution across the Melbourne region is available in the Australian Water Outlook.
Streamflow responses
Figure C5 Key flow gauging stations along the
main rivers within the Melbourne region
- There are four primary river catchments within the Melbourne region: Bunyip, Yarra, Maribyrnong and Werribee.
- Streamflows in the Maribyrnong, Werribee, and Yarra rivers are influenced by diversions for consumptive use, dam operations, and dam spills. The Bunyip River is less influenced by these factors.
Figure C6 Total monthly flow for major rivers in the Melbourne region during the 2021-22 year compared with the average and percentiles
- Streamflows during the 2021-22 year were above average for the third consecutive year.
- Throughout late winter and into spring, streamflows were relatively high across the region, particularly Werribee River at Wyndham Vale (Station 231204A), because of above average rainfall.
- Despite streamflow flow volumes decreasing after the new year, which is normal for the Melbourne region, streamflows remained average for the first six months of 2022.