National Water Account 2017

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Key findings

Climate and water

Water Accounting Statements

Supporting information

Region description

Reference information

Adelaide: Climate and water

About the region

The Adelaide region lies within southern Australia and 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).

Typically streamflow in the region's rivers reflects the distribution of rainfall throughout the year. Most storage inflows and streamflow occur during the winter months (July–August), and very little streamflow is observed during the dry summer months (December–February).

Climate conditions

Rainfall

Figure C1 Annual and montly rainfall deciles for the Adelaide region during the 2016–17 year

• Total area-averaged rainfall for the year was 785 mm, which is above the mean annual rainfall of 624 mm. Rainfall was very much above average for approximately 60% of the region during 2016–17.
• Low pressure troughs and intense low pressure systems in mid and late September 2016 resulted in many areas reporting their wettest September on record.
• Storm events in late-December 2016 contributed to high rainfall and widespread power outages across the region, particularly in the Adelaide Hills and metropolitan area.

Figure C2 Total monthly rainfall for the Adelaide region during the 2016–17 year compared with the long-term average and percentiles for the region

• In the first four months of the year (July–October 2016), the climate was influenced by a negative Indian Ocean Dipole phase that is associated with higher winter-spring rainfall. Rainfall across the Adelaide region was mostly above average during this 4-month period.
• Area-averaged rainfall for September 2016 was the highest on record for that month.
• Rainfall in June 2017 was well below the 10th percentile due to dominant high pressure systems that reduced the number of cold fronts and lows that typically occur across the region.

Actual evapotranspiration

Figure C3 Annual and monthly actual evapotranspiration deciles for the Adelaide region during the 2016–17 year

• Total area-averaged actual evapotranspiration was 689 mm, well above the mean value of 553 mm. Actual evapotranspiration was very much above average for approximately 90% of the region during 2016–17.
• The above-average evapotranspiration may be attributed to a combination of above-average temperatures across the region and increased water availability due to the high rainfall during the year.

Figure C4 Total monthly actual evapotranspiration for the Adelaide region during the 2016–17 year compared with the long-term average and percentiles for the region

• Average actual evapotranspiration was well above average during October–February, when water availability was high due to relatively high rainfall during spring and summer.

Soil moisture

Figure C5 Annual and monthly soil moisture deciles in the root zone (0–1m depth) for the Adelaide region during the 2016–17 year

• Soil moisture in the root zone (0–1m depth) was above average across the entire region.
• Rainfall and soil moisture are typically closely aligned. For example, above-average soil moisture from July 2016–March 2017 reflects the above-average rainfall that occurred during the majority of that period.
• Below average rainfall in June 2017 resulted in a region-wide soil moisture decrease.
• 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

• Myponga and Onkaparinga rivers provide the major inflows into the Myponga and Mount Bold reservoirs respectively.
• Flow along the North Para River 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

• Above-average streamflow ocurred during July–October 2016 in all major rivers, reflecting the relatively high rainfall experienced across the region during that 4-month period.
• The well above-average flows during September–October 2016 were due to heavy rainfall associated with several low pressure systems that occurred over the region.

Major water reforms

Adelaide Plains water allocation plan

• The development of a combined water allocation plan for Central Adelaide Prescribed Wells Area and Northern Adelaide Plains Prescribed Wells Area has been carried out by the Adelaide and Mount Lofty Ranges Natural Resources Management Board and South Australian Department of Environment, Water and Natural Resources.

Northern Adelaide Irrigation Scheme

• The Northern Adelaide Irrigation Scheme (NAIS) presents an opportunity to expand the use of recycled water in the Northern Adelaide Plains.
• The scheme will make available an extra 12,000 ML of water from the Bolivar Wastewater Treatment Plant to be used to expand horticultural irrigation in the Northern Adelaide Plains.
• Funding has been secured through the National Water Infrastructure Development Fund and the State Government has committed $110 million. Further information on the proposal is available at SA Water current projects website.

Unbundling water rights

• Progressive separation of water rights pursuant to Action 61 of the Water for Good plan has been carried out, so they can be managed as follows;
  • Water access entitlement (water licence): a right to a specified share of available water.
  • Water allocation: a right to take a specified volume of water in a specified period.
  • Water resource works approval: a right to construct, operate and maintain infrastructure to take water.
  • Site use approval: a right to use water at a particular location.

(refer to the Department of Environment, Water and Natural Resources website for further information).