Sydney: Climate and water
- Total annual rainfall was below average across the region for the third consecutive year.
- Streamflows were very low reflecting the below-average rainfall and poor soil moisture conditions.
- Annual streamflow in the Shoalhaven River was the lowest on record.
For further information on the region's climate and water conditions during the 2018–19 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 2018–19 year
- Total area-averaged rainfall for the year was 721 mm, less than the mean value of 890 mm.
- Rainfall was very low during July 2018 and April 2019 across almost the entire region.
- The below-average rainfall throughout the spring 2018 and winter 2019 months were likely due to a positive phase of the Indian Ocean Dipole that influenced Australia's climate during those periods (see the Bureau's 2018–19 Climate Report for more information).
- High rainfall during October–November 2018, as well as March 2019, was associated with low pressure systems and thunderstorm activity that impacted the region during these periods.
Figure C2 Total monthly rainfall for the Sydney region during the 2018–19 year compared with the average and percentiles for the region
- Rainfall in July 2018 and April 2019 was very low and well below the 10th percentile. It was the driest July since 1971 and the fourth driest April on record.
- Approximately 80% of the total annual rainfall occurred during the 6-month period between October 2018–March 2019.
Actual evapotranspiration
Figure C3 Annual and monthly actual evapotranspiration deciles for the Sydney region during the 2018–19 year
- Total area-averaged actual evapotranspiration was average to below average across most of the region reflecting the dry conditions and low water availability across the region throughout the year.
- Above-average evapotranspiration only occurred across the region during December 2018–January 2019; some areas in the north experienced their highest evapotranspiration on record for those months. This was due to a combination of very high temperatures across the region during this period, as well as increased water availability following the high rainfall during October–November 2018.
Soil moisture
Figure C4 Annual and monthly soil moisture deciles for the Sydney region during the 2018–19 year
- Soil moisture in the root zone (0–1 m depth) was well below average across most of the region; some areas in the south experienced their poorest soil moisture conditions on record.
- Rainfall and soil moisture are typically closely aligned. For example, the well below-average soil moisture across the entire region during July–September 2018 is due to the low rainfall that occurred during this 3-month period.
- Soil moisture conditions during the year were only above average in December 2018 following the high rainfall during October–November 2018.
- More information on soil moisture distribution across the Sydney region is available in the Australian Landscape Water Balance.
Streamflow responses
Figure C5 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.
- Streamflow along these rivers upstream of the above gauging stations is unregulated and not influenced by diversions for consumptive use.
Figure C6 Total monthly flow for key rivers during the 2018–19 year compared with the average and percentiles
- Streamflows were well below average for most of the year, which reflects the low rainfall and poor soil moisture conditions experienced across the region.
- Total annual flow in the Shoalhaven River at Warri (Station 215002) was 15 GL compared to the average value of 229 GL. This was the river's lowest annual flow on record.
- The very high rainfall during October–November 2018 had little effect on streamflow in these rivers, particularly in the Shoalhaven River. The very dry soil moisture conditions across the region during the winter–spring months meant much of the rainfall that occurred was soaked up by the soil.