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National Water Account 2019

Perth: Geographic information

  • The Perth region is home to waterways and wetlands of national significance.
  • Groundwater is the main source of water supply.
  • The region has experienced a decline in rainfall over the past four decades, resulting in increased reliance on climate resilient water sources, including desalination and groundwater replenishment.
Map showing the following summary information for the Perth region. Water use: 5 % of Australia's water use. Land use: 68% of the region used for grazing, agriculture, and forestry. Ecosystems: 3 Ramsar-listed wetlands with strong ecological significance. Water resources: 70% of water is sourced from groundwater.

For further geographic information about the region scroll down this page or click on the links below:

 

General description

Area : 21,436 km2
Population : 2.1 million (Australian Bureau of Statistics [ABS] 2016)

 

Map showing the key water features of the Perth region. The Perth region is in southwestern Australia and its boundary is defined mainly by three surface water catchments. These are:Swan Coast, in the northern part of the region Murray River in the central and southeastern part, and Harvey River in the south. A small part of the Moore-Hill Rivers catchment is also in the north of the region and the Collie River catchment in the south.

Figure R1 Contextual map of the Perth region

 

Lake Joondalup, Perth region. Source: Department of Water © Lindsay Preece

  • The Perth region is located on the west coast of Western Australia and is defined mainly by the Swan–Canning, Murray and Harvey river catchments.
  • The Darling escarpment runs in a north–south direction, splitting the region between the Darling Range to the east and the coastal plan to the west.
  • The Swan and Canning rivers and the Peel–Harvey estuarine system have strong environmental, cultural, and recreational significance.
  • The Gnangara and Jandakot groundwater systems are important sources of public and self-supply of water and support numerous groundwater-dependent wetlands.

 

Map showing the location of the Integrated Water Supply Scheme network and the Harvey Water Irrigation Area within the Perth region. Most of the trunk mains of the Integrated Water Supply Scheme are in the Perth metropolitan area in the northern part of the region near the coast. There are two desalination plants: Perth Seawater Desalination Plant near Kwinana about 30 km south of Perth and Southern Seawater Desalination Plant near Binningup in the southern part of the region. The Harvey Water Irrigation Area is also located in the southern part of the region near the town of Harvey.

Figure R2 The integrated Water Supply Scheme and the Harvey Water Irrigation Area within the Perth region

 

  • The Integrated Water Supply Scheme, operated by the Water Corporation, supplies potable water to the Perth metropolitan area.
  • The region has two desalination plants that supply water to the Integrated Water Supply Scheme.
  • The Harvey Water Irrigation Area in the south of the Perth region supports three irrigation districts near Harvey.

 

Land use

Map showing the distribution and land use types within the Perth region. The major urban centre is Perth, located in the northern part of the region along the coast. Outside of the Perth metropolitan area, forestry is the main land use and that occurs throughout the entire region. Areas of conservation and natural environments, as well as dryland agriculture, also occur throughout the region. Smaller areas of grazing occur mainly throughout the coastal floodplain.

Figure R3 Land use in the Perth region

 

  • Most urban land use in the region is in the Perth metropolitan area, including Mandurah, Rockingham and Pinjarra.
  • The Harvey Water Irrigation Area is about 400 km2 in area and has around 100 km2 under permanent irrigation for dairy farming, beef grazing, and horticulture.
  • Other major land uses in the Perth region include forestry, conservation and natural environments (particularly in the Darling Range), dryland agriculture and grazing.

 

Significant aquatic ecosystems

Map showing the locations of significant wetlands within the Perth region. There are three Ramsar-listed wetlands in the region: Forrestdale and Thomsons Lakes about 20 km south of Perth in the central part of the region near the coast; Peel–Yalgorup wetland system located on the coast near Mandurah about 50 km south of Perth; and Becher Point wetlands about 10 km south of Rockingham located halfway between Perth and Mandurah. There are also more than 20 nationally-important wetlands along the region's coastal plain.

Figure R4 Significant wetlands in the Perth region

 

  • The Perth region has a number of significant aquatic ecosystems, many of which are part of the superficial groundwater system on the coastal plain.
  • There are three designated Ramsar wetlands within the Perth region: Forrestdale and Thomsons lakes; Peel–Yalgorup wetland system; and Becher Point wetlands.

 

Water resources

Groundwater

  • Most of the region's water supply comes from groundwater.

 

A simplified three-dimensional cross-section image of the Perth region's groundwater aquifers. The section is taken over the Gnangara Mound on the coastal plain in the northern part of the region. The image shows that the region's aquifers are made up of several layered geological formations. The uppermost layer is the superficial aquifer. Beneath that lies the Leederville and Yarragadee aquifers, which are confined by layers of Guildford clay. The confined aquifers extend from beneath the salt water interface near the coast and inland up to the granite rock formation at the Darling fault.

Figure R5 Subsection of the groundwater system within the Perth region

 

  • The groundwater system within the Perth region comprises the water table aquifer and confined aquifers.
  • The water table aquifer is referred to as the 'superficial aquifer' and is a major source of water for urban supply, agriculture, public parks and gardens.
  • The primary confined aquifers in the Perth region are the Leederville and Yarragadee aquifers, underlying the superficial aquifer over the majority of the coastal plain. Both are major sources of water for urban supply and the Leederville aquifer is also widely used for open space irrigation.

 

Surface water

Rivers

  • There are three major surface water resources in the Perth region: the Swan-Canning, Murray and Harvey rivers.

 

Map showing the locations of key gauging stations along the main rivers within the Perth region. Swan River at Walyunga, station number 616011, in the northern part of the region about 40 km upstream of Perth; Murray River at Baden Powell Water Spout, station number 614006, on the Darling Range in the region's south; and Harvey River at Clifton Park, station number 613052, in the southern part of the region on the coastal plain.

Figure R6 Key flow gauging stations along the main rivers within the Perth region

 

Figure R7 Mean monthly flows along the Swan, Murray, and Harvey rivers and mean monthly rainfall for the Perth region

 

  • The seasonal flow characteristics of the rivers within the Perth region reflect the distribution of rainfall over the year. Most of the streamflow usually occurs during a 4-month period between June and September.

 

Storages

  • A number of storages have been constructed along tributaries in the upper reaches of the river systems in the Darling Range for urban and irrigation scheme supply.

 

Map showing the locations of major storages within the Perth region. The Serpentine and South Dandalup reservoirs in the central part of the region, and the Wellington Reservoir in the south, are the region's larger storages with more than 50% of the region's total storage capacity. The remaining 12 storages, located across most of the region, are less than 100,000 ML in capacity.

Figure R8 Surface water storages in the Perth region; active storage capacity of each storage is also shown

 

  • Most of the storages within the Perth region are used for urban water supply to the Integrated Water Supply Scheme.
  • The Harvey Water Irrigation Scheme is supplied from four surface water storages located in the southern part of the region—Waroona, Drakes Brook, Logue Brook and Harvey—as well as Wellington Reservoir to the south of the region boundary.
  • Mundaring Reservoir, located in the northern part of the region, supplies water to the Goldfields and Agricultural region outside the Perth region boundary; therefore, this storage is not considered a surface water asset in the Perth region account.
  • For more information on storages, see the Bureau of Meteorology's Water storage website.

 

Desalinated water

  • Desalinated water for the Perth region comes from two desalination plants: the Perth Seawater Desalination Plant (capacity 45,000ML) and the Southern Seawater Desalination Plant (capacity 100,000 ML) (see Figure R2 above).

Southern Seawater Desalination Plant, Perth region. Source: Water Corporation © Water Corporation

  • The combined capacity of the two plants can now meet about half the region's annual urban water supply requirements.
  • For more details on desalinated water in the Perth region, see the Water Corporation website.

 

Wastewater recycling

  • Treated wastewater from several wastewater treatment plants throughout the Perth region is recycled. The primary uses of treated wastewater are: industrial use, particularly in the Kwinana Industrial Area; open space irrigation; on-site use at the treatment plants; and managed aquifer recharge (groundwater replenishment).
  • A groundwater replenishment scheme started operation in late 2017. The scheme treats wastewater to drinking water standards and recharges it back into the groundwater store for future use. For more information on groundwater replenishment, see the Water Corporation website.

 

Water systems

Urban water system

  • The urban water system within the Perth region, referred to as the Integrated Water Supply Scheme, is operated by the Water Corporation.
  • The system primarily supplies water to the Perth metropolitan area, including Mandurah and Harvey. It also supplies water to areas outside the Perth region boundary, including the Goldfields and Agricultural region and Western Australia's southwest region.
  • Water for the system is sourced from surface water storages and bore fields within the region and the region's two desalination plants.
  • For more information on the urban water system in the Perth region, refer to the Water Corporation website.

 

Irrigation scheme

  • Harvey Water is a private irrigators' cooperative that operates the Harvey Water Irrigation area in the south of the Perth region.
  • It has a bulk water licence to access a portion of the total capacity of each of the five storages used for the irrigation scheme.
  • The irrigation area includes three irrigation districts: Waroona, Harvey, and Collie River.
  • The Waroona and Harvey districts are supplied from four storages (Waroona, Drakes Brook, Logue Brook and Harvey) almost entirely via a piped system. The Collie River irrigation district is supplied by Wellington Reservoir mainly via a network of open channels.
  • For more information on the irrigation scheme, refer to the Harvey Water website.