Adelaide: Climate and water
- Rainfall was higher than average in July–August 2017; however, most of the other months of the year had below-average rainfall.
- Heavy rainfall over the southern portion of the region in August 2017 resulted in very high streamflows in the Onkaparinga and Myponga rivers during that month.
- Streamflows over the rest of the year were mostly below average, reflecting the below-average rainfall.
For further information on the region's climate and water conditions during the 2017–18 year scroll down this page or click on the links below:
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 monthly rainfall deciles for the Adelaide region during the 2017–18 year
- Total area-averaged rainfall for the year was 587 mm, below the mean value of 622 mm.
- Average annual rainfall occurred over the southern and eastern parts of the region. Below-average rainfall occurred over the northern part of the region.
- In the first three months of the year (July–September 2017) the climate was influenced by a negative Indian Ocean Dipole phase that is associated with higher winter-spring rainfall. Total rainfall across the Adelaide region during this 3-month period was well above average, particularly during August over the southern part of the region.
Figure C2 Total monthly rainfall for the Adelaide region during the 2017–18 year compared with the average and percentiles for the region
- More than 40% of the total annual rainfall occurred in July–August 2017. Rainfall in August was above the 90th percentile for that month. The majority of the rainfall during this period was associated with low pressure troughs and intense low pressure systems that impacted the region.
- Rainfall was below average for the rest of the year except for December.
Actual evapotranspiration
Figure C3 Annual and monthly actual evapotranspiration deciles for the Adelaide region during the 2017–18 year
- Total area-averaged actual evapotranspiration was average to below average across the region.
- The above-average evapotranspiration in July–October 2017 is likely due to increased water availability following high rainfall during July–August 2017. The region also experienced above average temperatures in July 2017 and October 2017 which may have contributed to the very much above average evapotranspiration in those months.
- Actual evapotranspiration was below average for the entire latter half of the year (January–July 2018), reflecting the dry conditions across the region during this period.
Soil moisture
Figure C5 Annual and monthly soil moisture deciles for the Adelaide region during the 2017–18 year
- Soil moisture in the root zone (0–1m depth) was below average across most of the region.
- Rainfall and soil moisture are typically closely aligned. Average to above-average soil moisture during August–September 2017 and in December 2017 is likely due to the high rainfall that occurred across the region during July–August and in December. The below-average soil moisture during January–June 2018 can be attributed to the relatively poor rainfall that occurred during the entire latter half of the year.
- More information on soil moisture distribution across the Adelaide region is available in the Australian Landscape Water Balance.
Streamflow responses
Streamflow
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 2017–18 year compared with the long-term average and percentiles
- The very high streamflow in the Onkaparinga and Myponga rivers in August 2017 was due to above-average rainfall associated with low pressure troughs and intense low pressure systems that occurred during July–August 2017, particularly over the southern and eastern parts of the region.
- Streamflow in the North Para River was well below-average throughout most of the year, reflecting the generally drier conditions across the north compared to the southern parts of 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.
- Construction started in April 2018 and the project is on track for completion in 2019. 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 that water rights can be managed as a water access entitlement, water allocation, water resource works approval or site use approval.
- Refer to the Department for Environment and Water website for further information.