National Water Account 2019

Adelaide: Climate and water

  • Total annual rainfall was below average, particularly across the northern part of the region.
  • Streamflows were low reflecting the below-average rainfall and poor soil moisture conditions.


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 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 occurs 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 2018–19 year 

 

  • Total area-averaged rainfall for the year was 495 mm, less than the mean value of 620 mm. Annual rainfall was the lowest on record in the northeastern part of the region.
  • Very dry periods during September–October 2018 and January–April 2019 contributed to the below-average annual rainfall for the region.
  • The below-average rainfall throughout the spring 2018 months was likely due to a positive phase of the Indian Ocean Dipole that influenced Australia's climate during this period (see the Bureau's 2018–19 Climate Report for more information).
  • Above-average rainfall that occurred across most of the region during November 2018 and May 2019 was due to heavy rainfall associated with low pressure systems and cold fronts that crossed the region during these periods.

 

Figure C2 Total monthly rainfall for the Adelaide region during the 2018–19 year compared with the average and percentiles for the region

 

  • Rainfall was below average most months of the year.
  • In September 2018, January 2019 and April 2019 rainfall was well below the 10th percentile and the lowest in more than 25 years for these months.

 

Actual evapotranspiration


Figure C3 Annual and monthly actual evapotranspiration deciles for the Adelaide region during the 2018–19 year

 

  • Total area-averaged actual evapotranspiration was below average across the entire region.
  • Well below-average evapotranspiration occurred across most of the region during February–April 2019 due to very dry conditions and low water availability during a 4-month period between January–April.
  • Above-average evapotranspiration only occurred across most of the region during December 2018 due to the increased water availability following high rainfall in November–December 2018.

 

Soil moisture


Figure C4 Annual and monthly soil moisture deciles for the Adelaide region during the 2018–19 year

 

  • Soil moisture in the root zone (0–1m depth) was well below average across most of the region; an area in the north experienced their poorest soil moisture conditions on record.
  • Rainfall and soil moisture are typically closely aligned. For example, very poor soil moisture conditions across the entire region during the 4-month period from January–April 2019 is due to well below-average rainfall that occurred during that period.
  • Average soil moisture conditions across the region only occurred in December 2018 and May–June 2019 following high rainfall in November 2018 and May 2019 respectively.
  • More information on soil moisture distribution across the Adelaide region is available in the Australian Landscape Water Balance.

 

Streamflow responses

Figure C6 Key flow gauging stations along the main rivers within the Adelaide 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 key rivers during the 2018–19 year compared with the long-term average and percentiles

 

  • Annual streamflows in the region's major rivers were well below average, which reflects the relatively low rainfall and poor soil moisture conditions experienced across the region. For example, total annual flow in the Onkaparinga River at Houlgrave (Station A5030504) was 30 GL compared to the average value of 70 GL.
  • Annual streamflow in the North Para River was the lowest in more than 50 years of record. No flow occurred in the river for almost the entire summer–autumn period.
  • The higher rainfall periods during the year had only a minor effect on streamflow, particularly in North Para River. 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.

 

Major water reforms

Northern Adelaide Irrigation Scheme

  • The Northern Adelaide Irrigation Scheme is a project that will expand the use of recycled water in the region.
  • Stage 1 of the project will deliver 12,000 ML of recycled water from the Bolivar Wastewater Treatment Plant for horticultural irrigation in the Northern Adelaide Plains.
  • Construction started in April 2018 and the project is on track for completion during the 2019–20 year. Further information on the proposal is available on the SA Water website.