Sydney: Climate and water

For the water account period 01 July 2022 - 30 June 2023

  • Total annual rainfall during the 2022-23 year was above average for the third consecutive year.
  • An East Coast Low produced signicant rainfall in July and, with the influence of a negative Indian Ocean Dipole and La Niña, spring rainfall across the region was also high.
  • Soil moisture in the root zone (0-1 m depth) was predominantly average to above average.
  • Total annual flows in the region's major rivers were above average, with streamflows being the highest on record in the Coxs River at Island Hill.

Schematic representation of the Sydney region. In 2021–22, rainfall was 1,236 mm, above average for the first time in five years. Streamflow in Shoalhaven River in 2021–22 was 747 GL compared to the average value of 231 GL. Soil moisture was above average.

For further information on the region's climate and water conditions during the 2022-23 year scroll down this page or click on the links below:

 

About the region

  • The Sydney region has a mild-to-warm temperate climate, characterised by cold to mild winters and warm to hot summers.
  • Rainfall is generally uniform throughout the year, but higher totals are more common in the summer and autumn months (December to May).
  • Streamflows in the region's rivers typically have perennial flows, reflecting the relatively uniform distribution of rainfall throughout the year.

 

Climate conditions

Rainfall

Figure C1 Annual and monthly rainfall deciles for the Sydney region during the 2022-23 year

  • Total area-averaged rainfall for the 2022-23 year was 1,095 mm, 23% above the mean value of 893 mm. It was the region's third consecutive year of above average rainfall.
  • An East Coast Low in the first week of July 2022 brought heavy rain to the region causing flash and riverine flooding. As a result, area-averaged July rainfall was four times the monthly mean and the third wettest on record.
  • A negative Indian Ocean Dipole event was declared between August and December 2022 (Climate Driver Update) and in September 2022, a third consecutive La Niña event was declared active in the tropical Pacific Ocean (Climate Driver Update) and remained active through to March 2023. A negative Indian Ocean Dipole and La Niña generally increase the chances of above average rainfall in winter to spring and spring to summer respectively.
  • The combined influence of the negative Indian Ocean Dipole and La Niña event enhanced rainfall across the region during spring, particularly during October when a series of low-pressure systems and surface troughs brought heavy rainfall contributing to the sixth highest October rainfall on record.
  • Despite above average rainfall in January 2023, summer rainfall was 20% below average.
  • While early to mid autumn rainfall was close to average, May and June 2023 were notably drier at about 30% of the monthly average.
  • More information on Australia's climate and water over the 2022-23 year can be found at: Financial year climate and water statement 2022-23.

 

Figure C2 Total monthly rainfall for the Sydney region during the 2022-23 year compared with the average and percentiles for the region

  • Rainfall was above the 90th percentile for July 2022 and October 2022 and equal to the 90th percentile in September.
  • No month ranked below the 10th percentile, however, December 2022, May 2023, and June 2023 were all considerably dry for their respective months.

 

Actual evapotranspiration

Figure C3 Annual and monthly actual evapotranspiration deciles for the Sydney region during the 2022-23 year

  • Total area-averaged actual evapotranspiration for the 2022-23 year was predominantly very much above average across the region, largely driven by high rainfall increasing landscape water availability.
  • With very high monthly rainfall totals across the region, evapotranspiration in July 2022 was very much above average, with some areas experiencing their highest evapotranspiration on record.
  • Evapotranspiration remained above average through to November 2022 due continued significant rainfall events boosting water availablity.
  • From December 2022 to May 2023, evaporation was closer to average with patches of above average evapotranspiration reflecting the rainfall distrubution during this period.
  • By June 2023, following two months of below average rainfall, evapotranspiration was below average for much of the northern half of the region, with only the southwestern part of the region remaining above average.

 

Soil moisture

Figure C4 Annual and monthly soil moisture deciles for the Sydney region during the 2022-23 year

  • Soil moisture in the root zone (0–1 m depth) for the 2022-23 year was mostly average to above average, except for some areas in the southeast of the region which experienced below average soil moisture.
  • With heavy rainfall from an East Coast Low early in the month, soil moisture during July 2022 was very much above average apart from in the most southern part of the region.
  • From August 2022 through to November 2022, continued high rainfall resulted in soil moisture remaining predominantly above average.
  • With closer to average rainfall conditions through summer, soil moisture was average to below average, a drying trend that continued into autumn.
  • By June 2023, following two months of low rainfall, soil moisture for large parts of the region's east was very much below average.
  • More information on soil moisture distribution across the region is available in the Australian Water Outlook.

 

Streamflow responses

Map of key gauging stations. Coxs River at Island Hill, station number 212045, is in the northwestern part of the region south of Lithgow. Shoalhaven River at Warri, station number 215002, is in the southern part of the region.
Figure C5 Key flow gauging stations along the main rivers within the Sydney region

  • The Hawkesbury–Nepean and Shoalhaven river systems are the two primary river systems within the Sydney region.
  • Streamflow along these rivers upstream of the gauging stations is unregulated and not influenced by diversions for consumptive use.
  • Coxs River flows into the region's largest storage (Warragamba).

 

Figure C6 Total monthly flow for major rivers in the Sydney region during the 2022-23 year compared with the average and percentiles

  • Total annual flows in the Coxs River at Island Hill (Station 212045) were the highest on record, while the total annual flows in the Shoalhaven River at Warri (Station 215002) were 71% above average.
  • Following heavy rainfall in the first week of the month, Coxs River at Island Hill recorded its highest July streamflow on record at more than seventeen times the monthly average flow. Rainfall totals were not as high in the southern part of the region which was reflected in the closer to average flows in Shoalhaven River.
  • Spring streamflows at both sites were near or above the 90th percentile in response to heavy rainfall on wet catchments. Streamflows in the Coxs River at Island Hill during August 2022, October 2022 and November 2022 were the highest on record for those respective months.
  • Below-average rainfall during the last six months of the 2022-23 year (January to June 2023) resulted in streamflows being average to below average, but above the 10th percentile for both sites.