Sydney: Climate and water
More than 30% of the annual rainfall occurred in March 2017. Flash flooding and very high streamflows occurred in some parts of the region during this month. Rainfall and streamflow throughout most of the year were below average.
For further information on the region's climate and water conditions during the 2016–17 year scroll down this page or click on the links below:
About the region
The Sydney region has a temperate climate with warm summers (December–February) and mild winters (June–August). Rainfall occurs throughout the year with most rainfall occurring during the summer and autumn months. Higher streamflows typically occur during these months..
Climate conditions
Rainfall
Figure C1 Annual and monthly rainfall deciles for the Sydney region during the 2016–17 year
- Total area-averaged rainfall for the year was 861 mm, which was slightly less than the mean annual rainfall of 897 mm.
- Very high rainfall occurred in March 2017, primaily due to persistent heavy rainfall and thunderstorms during the entire month. Some parts of the region experienced their highest March rainfall on record.
Figure C2 Total monthly rainfall for the Sydney region during the 2016–17 year compared with the long-term average and percentiles for the region
- Rainfall was below average for most of the 2016–17 year.
- March 2017 rainfall was above the 90th percentile and almost three times the average for the month.
Actual evapotranspiration
Figure C3 Annual and monthly actual evapotranspiration deciles for the Sydney region during the 2016–17 year
- Total area-averaged actual evapotranspiration was 755 mm, marginally higher than the mean value of 734 mm.
Figure C4 Total monthly evapotranspiration for the Sydney region during the 2016–17 year compared with the long-term average and percentiles for the region
- Actual evapotranspiration was above average for most months of the year.
- Evapotranspiration was only below average during December–February when water availability was low due to relatively poor rainfall during spring and summer.
Soil moisture
Figure C5 Annual and monthly soil moisture deciles for the Sydney region during the 2016–17 year
- Soil moisture in the root zone (0–1 m depth) was average to above average across the region.
- Rainfall and soil moisture are typically closely aligned. For example, very much above-average soil moisture during March–April 2017 reflects the high rainfall that occurred during March.
- More information on soil moisture distribution across the Sydney region is available in the Australian Landscape Water Balance.
Streamflow responses
Streamflow
Figure C6 Key flow gauging stations along the main rivers within the Sydney region
- The Hawkesbury–Nepean and Shoalhaven river systems are two primary river systems within the Sydney region.
- Flow along these rivers upstream of the above gauging stations is unregulated and not influenced by diversions for consumptive use.
Figure C7 Total monthly flow for key rivers during the 2016–17 year compared with the long-term average and percentiles
- In both the Grose and Shoalhaven rivers, streamflow was below average for the majority of the year.
- The well above-average monthly flow during March 2017 was due to persistent heavy rainfall and thunderstorms during the entire month. Higher rainfall occurred in the northern part of the region. Consequently, flows in the Grose River in March were relatively much higher than flows in the Shoalhaven River.