National Water Commission

The Patawalonga water management area is a groundwater management unit (~231 km²) consisting of the Adelaide metropolitan and surrounding areas (total population ~1,124,000) to the west of the Mt Lofty Ranges (See Figure 1). It is a subset of the Adelaide water supply area. The main drainage features in the area are the Sturt River and Brownhill Creek, with discharge to the ocean via the Patawalonga stormwater outlet. Urban stormwater is a significant input to surface water.

The total transfer of water into the water management area is ~65,000 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 water management area.

Groundwater is recharged largely in the Adelaide hills in the southeast part of the catchment and moves towards the coast.

Overall, water is managed by the South Australian Department of Water, Land and Biodiversity Conservation with bulk water supplied by SA Water.




Figure 1 Patawalonga water management 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 (Table 1).

Rainfall in 2004-05 was 553 mm, which is about 97% of the long term average and about 99% of the rainfall over the last 10 years (Figure 2). Rainfall decreases rapidly across the water management area towards the coast (~60% decline). Rainfall in the area occurs primarily during the winter (Figure 3).

Runoff in the area is a mixture of runoff and stormwater in the Adelaide City portion of the catchment. During 2004-05, streamflow in the water management area was above average (Figure 4). This may be the result of increased large rainfall events (see June rainfall in Figure 3) which tend to result in larger than normal surges of stormwater.

Groundwater levels in the water management area are seasonally variable and have shown a slow decline over the past 50 years (Figure 5). This is probably the result of a decrease in groundwater recharge due to the increasing urbanisation of Adelaide.

Table 1 Summary of Patawalonga water management area contextual information

Figure 2 Annual rainfall for the Patawalonga water management area (modified from BOM, 2006)




Figure 3 Monthly rainfall and evaporation for the Patawalonga water management area (modified from BOM, 2006 & Climate Atlas)




Figure 4 Representative streamflow hydrograph for the Patawalonga water management area for Sturt River U/S Minno Creek Junction (gauge A5040518)




Figure 5 Representative hydrograph for the Patawalonga water management area

Summary of the total water resources in the basin

The total volumes of water in the Patawalonga WMA are shown in Table 2. Flow for the Sturt River and Brownhill Creek in 2004-05 was slightly above the long term average.

Table 2 Summary of water balance in the Patawalonga water management area, 2004-05

Figure 6 Water balance summary diagram for Patawalonga water management area

Outcomes from the water cycle report

The following information becomes apparent from Table 2.

• Urban stormwater was the main component of surface water outflow in the Patawalonga water management area.
• Groundwater discharge was significantly higher than recharge due to groundwater mining of the tertiary aquifer. This resulted in a decrease in aquifer storage during 2004-05.
• The error item for this catchment was low at 8%.
• Groundwater pumping was not well understood and as such was estimated. Groundwater discharge was from a pre development model.
• 65,000 ML of surface water was transferred into the WMA from storages outside the catchment and the River Murray to provide for the Adelaide water supply.
• Water 2010 estimates for recharge and surface water runoff were too low and high respectively and were not used.
• Approximately 88% of groundwater recharge was discharged to surface water as baseflow.
• 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
• Some groundwater extraction volumes
• Farm dams

Download 2004-05 water cycle report: