Adelaide: Climate and water overview
Climate conditions
Rainfall
The total area-averaged rainfall over the Adelaide region during the 2014–15 year was 445 mm, which is very much below the long-term area-averaged rainfall of 633 mm (based on the 1900–2015 period). Rainfall ranged from more than 600 mm in the south eastern part of the region to less than 300 mm in the northwest (Figure C11).
Figure C11 Total annual rainfall for the Adelaide region during the 2014–15 year
Rainfall in 2014–15 year was the lowest on record in a small area along the coastal edge in the south west of the Adelaide region (Figure C12). The conditions represent a decrease in rainfall compared to the 2013–14 year (see 2014 National Water Account), where total area-averaged rainfall was 712 mm. The decrease in rainfall in 2014–15 contributed to below average flows in the major river systems in the region (see Streamflow responses) as well as decreased inflows into the major water storages during the year (see Surface water store of the 'Supporting information' note).
Figure C12 Annual and monthly rainfall deciles for the Adelaide region during the 2014–15 year
Generally below average rainfall conditions were experienced across much of southeastern Australia during the 2014–15 year. Climate across Australia was largely influenced by persistent near El Niño conditions in the Pacific Ocean from late-2014 and the Bureau declared an El Niño event in May 2015.
During the 2014–15 year, below average to very much below average rainfall was recorded for most months of the year (Figure C13). Despite above average rainfall during July 2014, January and April 2015, and average rainfall during May 2015, annual rainfall was still very much below average.
Figure C13 Total monthly rainfall for the Adelaide region during the 2014–15 year compared with the long-term average and percentiles for the region
Evapotranspiration
The total area-averaged potential evapotranspiration over the Adelaide region during the 2014–15 year was 1,821 mm, which is slightly above the long-term area-averaged potential evapotranspiration of 1,805 mm (based on the 1911–2015 period). Potential evapotranspiration was higher in the northern parts of the region and lowest in the south of the Adelaide region (Figure C14).
Figure C14 Total annual evapotranspiration for the Adelaide region during the 2014–15 year
Potential evapotranspiration was average across most of the region and below average in the southern parts of the region (Figure C15).
Figure C15 Annual evapotranspiration deciles for the Adelaide region during the 2014–15 year
Soil moisture
Figure C16 shows that soil moisture, in the root zone (0 to 1m depth) during the 2014–15 year was below average across most of the Adelaide region and average in the north and far southeast areas of the region (compared with the 1911–2015 period).
Figure C16 also shows monthly soil moisture deciles in the root zone (0 to 1m depth) during the 2014–15 year. Soil moisture conditions declined compared to the previous year in most areas of the Adelaide region due to below average rainfall experienced across much of the 2014–15 year.
The impact of these drier conditions is demonstrated by the below average streamflows in major rivers across the region (see Streamflow responses). Groundwater flows were also typically lower in 2014–15 when compared to the previous year (see Groundwater store in the 'Supporting information' note), as rainfall would have replenished soil moisture before producing runoff into rivers, or contributing to recharge/discharge volumes.
More information on soil moisture distribution across the Adelaide region is available in the Australian Landscape Water Balance.
Streamflow responses
During the 2014–15 year, total annual streamflow in the Adelaide region was below, to well below the mean annual flow for three rivers.
Streamflow
There are three primary river systems within the Adelaide region:
- Myponga
- North Para
- Onkaparinga.
Monthly streamflow for the Myponga (Station A5020502), North Para (Station A5050502) and Onkaparinga (Station A5030504) is presented in figures C17–C19. The locations of the streamflow gauges used to prepare these hydrographs are shown in Figure C4 in 'Contextual information'.
Figure C17 Monthly flow along the Myponga River during the 2014–15 year compared with the long-term average and percentiles for the river
Figure C18 Monthly flow along the North Para River during the 2014–15 year compared with the long-term average and percentiles for the river
Figure C19 Monthly flow along the Onkaparinga River during the 2014–15 year compared with the long-term average and percentiles for the river
Figures C17-C19 show that flow was quite variable throughout the year and reflected the rainfall observed in the Adelaide region. At the start of the 2014–15 year, very much above average streamflows were observed in the North Para and Onkaparinga rivers, and average flows in the Myponga River. Streamflow in late winter and spring was well below average across all rivers. Streamflows across the summer and autumn months were below average for the Myponga and North Para rivers, continuing until the end of the year (early winter). In contrast, summer/autumn streamflows in the Onkaparinga River were generally average to below average.
Major water reforms
Ongoing major water reforms in the Adelaide region include the unbundling of water rights and development of the Adelaide Plains water allocation plan, described in detail below. SA Water also has several projects ongoing, that are ultimately aimed at achieving efficiencies in water treatment and reuse. Refer to the SA Water current projects website for further information.
Adelaide Plains water allocation plan
Ongoing development of combined water allocation plan for Central Adelaide PWA and Northern Adelaide Plains PWA has been carried out by the Adelaide and Mount Lofty Ranges NRM Board and Department of Environment, Water and Natural Resources.
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 four separate items (refer to the Department of Environment, Water and Natural Resources website for further information).