Adelaide: Climate and water

  • Total annual rainfall was below average for the fourth consecutive year.
  • Streamflows were low reflecting the relatively dry conditions over the region.

Schematic representation of the Adelaide region. In 2020–21, rainfall was 516 mm, less than average for the fouth consecutive year. Streamflow in Onkaparinga River in 2020–21 was 56 GL compared to the average value of 70 GL. Soil moisture was below average.

For further information on the region's climate and water conditions during the 2020–21 year scroll down this page or click on the links below:

 

About the region

  • The Adelaide region generally experiences mild winters and warm, dry summers. Most of the rainfall in the region falls from May–September. Rainfall can be unreliable and infrequent during summer (December–February).
  • Streamflow in the region's rivers generally reflects the distribution of rainfall throughout the year. Most of the streamflow and storage inflow occur during the winter months (June–August) and very little streamflow is observed during the dry summer months (December–February).

 

Climate conditions

Rainfall

Figure C1 Annual and monthly rainfall deciles for the Adelaide region during the 2020–21 year

 

  • Total area-averaged rainfall for the year was 516 mm, less than the mean value of 629 mm.
  • In July 2020, rainfall was well below average across the entire region, which contributed to the region's driest winter in five years.
  • Below-average rainfall across almost the entire region during April–May 2021 contributed to the region's second driest autumn on record and the driest since 2005.
  • Above-average rainfall in June 2021 was likely due to a negative Indian Ocean Dipole pattern that influenced Australia's climate during this period.

 

Figure C2 Total monthly rainfall for the Adelaide region during the 2020–21 year compared with the average and percentiles for the region

 

  • Rainfall was above average in October 2020, February 2021 and June 2021. All other months had below-average rainfall.

 

Actual evapotranspiration

Figure C3 Annual and monthly actual evapotranspiration deciles for the Adelaide region during the 2020–21 year

 

  • Total area-averaged actual evapotranspiration was average to below average across the region.
  • Evapotranspiration was average to below average throughout most of the year reflecting the dry conditions and low water availability, particularly during the first part of summer (December 2020–January 2021) and late-Autumn (May 2021).
  • Evapotranspiration was above average over large parts of the region during February–March 2021 due to increased water availability following the high rainfall in February 2021.

 

Soil moisture

Figure C4 Annual and monthly soil moisture deciles for the Adelaide region during the 2020–21 year

 

  • Soil moisture in the root zone (0–1 m depth) was average to below average across the region.
  • Soil moisture was below average over most of the region during August–September 2020 following low winter rainfall.
  • In February 2021, soil moisture was above average following the high rainfall during that month.
  • By May 2021, soil moisture was well below average over large parts of the region following one of the region's drier autumns on record.
  • More information on soil moisture distribution across the Adelaide region is available in the Australian Landscape Water Balance.

 

Streamflow responses

Map of key gauging stations. North Para River at Yaldara, station number A5050502, is in the northern part of the region near the town of Gawler. Onkaparinga River at Houlgrave, station number A5030504, is in the central part of the region.
Figure C5 Key flow gauging stations along the main rivers within the Adelaide region

 

  • Onkaparinga River provides the major inflows into Mount Bold Reservoir—the region's largest storage.
  • Flow along the North Para River is unregulated and not influenced by diversions for consumptive use.

 

Figure C6 Total monthly flow for major rivers in the Adelaide region during the 2020–21 year compared with the average and percentiles

 

  • Annual streamflows in the region's major rivers were well below average reflecting the relatively dry conditions throughout the year, particularly during the 2020 winter months.
  • Annual streamflow in the North Para River was very low for the third consecutive year. No flow occurred in the river for almost the entire summer–autumn period.
  • The higher rainfall periods during October 2020 and February 2021 had only a minor effect on streamflow. The very dry soil moisture conditions across the region during most of the year meant much of the rainfall that occurred was soaked up by the soil.

* SA Department for Environment and Water reported that  data for Station A5030504 were missing from January 24 to 23 April 2021 due to the Cherry Gardens fire in January 2021 and to when the station received major damage and was unsafe to access. The data used here were the combination of stations A5030504 and A5030504AA.1 (data mostly not validated and there were some spikes in flow in November 2020 – January 2021). Therefore, the total streamflow volume (financial year 2020–2021) included flows from July 2020 to October 2020 and May–June 2021.