National Water Commission

The Adelaide water supply area has an area of ~3127 km² and consists of the following WMAs, Northern Adelaide Plains, Little Para, Yatla, McLaren Vale PWA, Parra Wirra, Lower Torrens, Upper Torrens, Patawalonga, Onkaparinga, Myponga and Adelaide. Like any metropolitan supply area it consists of a complex array of supply, storage and delivery systems that has grown with the city (Figure 107). Total population of the water supply area is ~1,066,100 (ABS 2001 Census).

The main drainage features in the area are the River Torrens, Onkaparinga River and the Sturt River, which all discharge to the ocean. Urban stormwater is also a significant input to surface water with a number of natural creeks discharging to stormwater drains.

The total transfer of water into the WMA is ~165,000 ML. In normal years, 60% of this water comes from runoff in the Mt Lofty Ranges with an additional 40% coming from the River Murray, though in dry years this percentage can increase to 90% (http://www.sawater.com.au/SAWater/Education/OurWaterSystems/Pipelines.htm). While the water delivery system in South Australia consists of a number of reservoirs, there are no major reservoirs located in the WMA.

Groundwater recharges largely in the Adelaide hills in the southeast part of the WSA and moves towards the coast.

Overall, water management is by the South Australian Department of Water, Land and Biodiversity Conservation with bulk water supplied by SA Water. Figure 2 shows the major storages, pipelines from the Murray and water supply distribution network in the Adelaide water supply area.



Figure 1 Adelaide water supply area locality map

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There were permanent water conservation measures during 2004 05. Rainfall and streamflow was close to the long term average.

Rainfall in 2004 05 was 567 mm (Table 1), which is about 97% of the long term average and about 99% of the rainfall over the last 10 years (Figure 3). Rainfall decreases rapidly across the WMA towards the coast (~60% decline). Rainfall in the area occurred primarily during the winter (Figure 4).

Runoff in the area is a mixture of runoff and stormwater in the Adelaide City portion of the water supply area. During 2004 05, streamflow in the WMA was below average on the Onkaparinga River (Figure 5) and about average on Scott creek Figure 6.

Groundwater levels in the WMA are seasonally variable and have shown a slow decline over the past 50 years (Figure 7). This is probably the result of a decrease in groundwater recharge due to increasing urbanisation in Adelaide.

Due to a combination of permanent water conservation measures and an increased reliance on recycled water, Adelaide has reduced its per capita water use from ~500 litres/person/day in 2000/01 to ~410 litres/person/day in 2004/05 (Figure 8).

Table 1 Summary of Adelaide water supply area contextual information

Figure 3 Annual rainfall for the Adelaide water supply area (modified from BOM, 2006)




Figure 4 Monthly rainfall and evaporation for the Adelaide water supply area (modified from BOM, 2006 & Climate Atlas)




Figure 5 Representative streamflow hydrograph for the Adelaide water supply area for Onkaparinga River at Houlgrave (gauge 5030504)





Figure 6 Representative streamflow hydrograph for the Adelaide water supply area for Scott Creek (gauge 5030502)




Figure 7 Representative hydrograph for the Adelaide water supply area




Figure 8 Total water supplied by SA Water to Adelaide compared to population from 1999-2000 – 2004-05 (source: WSAA, 2005)

Summary of the Total Water Resources in the Basin

Table 2 Summary of water balance in Adelaide water supply area, 2004-05

Figure 8 Water balance summary diagram for the Adelaide Water Supply System

Outcomes from the water cycle report

The following information becomes apparent from Table 2. 

• The Adelaide water supply area balance was a complex mix of water use, inter-basin transfers, and surface water / groundwater interaction with the majority of water sourced from the River Murray.
• There was about 16,000 ML of additional water in storage at the end of 2004-05.
• Rainfall was more or less the same as the long term average during 2004-05.
• Surface water runoff and baseflow were equal to surface water outflow.
• The error term was low, representing about 8% of the total inflows.
• Captured rainfall, extractions and diversions and outflow estimates dominated the water balance representing more than 74% of the overall balance. The Water 2010 estimates were generally too low with an accuracy of ±100% (Category D) and were not used.
• A large volume of water (110,000 ML/yr) was transferred into the area from the Murray-Darling Basin.
• 30% of groundwater recharge was discharged to surface water as baseflow.
• Future water balance assessments would benefit from increased knowledge of groundwater storages. • ABS water entitlement information was not available for the entire Adelaide water supply area.
• Data could not be obtained for the following items in the water balance:
• Groundwater storage volumes (renewable and non-renewable)
• Soil - unsaturated zone storage volumes
• River channels storage volumes
• Seepage from streams to groundwater
• Irrigation recharge
• Some groundwater extraction volumes

Download 2004-05 water cycle report: