Perth
Physical information
General description
Area: 21,156 km2
Population: 1.9 million (Australian Bureau of Statistics [ABS] 2013)
The Perth region is located on the west coast of Western Australia (Figure P1). The boundary of the region is mostly defined by three surface water catchments (Figure P2):
- Swan Coastal
- Murray River
- Harvey River.
The Perth region boundary also includes a small part of the Moore–Hill Rivers and Collie River catchment areas (Figure P2). These areas were included in the boundary to capture the groundwater management areas and two irrigation districts within the Harvey Water Irrigation Area.
Figure P1 Location map of the Perth region within Australia
Figure P2 Contextual map of the Perth region
The Darling escarpment is a geographic feature that splits the region in half. The escarpment runs in a north–south direction and rises to more than 200 metres above sea level. To the east is the Darling Range (indicated by the lighter coloured shading in Figure P2), which extends to the eastern boundary of the region, and to the west is the coastal plain.
The region is home to waterways and wetlands of national significance. The Swan and Canning rivers and the Peel–Harvey estuarine system (Figure P2) have strong environmental, cultural, and recreational significance. There are also important groundwater resources in the region, such as the Gnangara and Jandakot groundwater systems. These aquifers are a source of public and self-supply and support numerous groundwater-dependant wetland ecosystems.
Other significant water features within the region include:
- the Integrated Water Supply Scheme, operated by the Water Corporation, which supplies potable water to the Perth metropolitan area (as well as areas outside the Perth region boundary)
- two irrigation districts, Waroona and Harvey, located in the southern area of the Perth region within the Harvey Water Irrigation Area
- the Perth Seawater Desalination Plant near Kwinana and the Southern Seawater Desalination Plant near Binningup that supply water to the Integrated Water Supply Scheme.
The Integrated Water Supply Scheme and the Harvey Water Irrigation Area are shown in Figure P3.
Figure P3 Map of the Integrated Water Supply Scheme and the Harvey Water Irrigation Area within the Perth region
The Perth region is physically defined above (see Figure P2), and includes the Swan Coastal, Murray River, and Harvey River catchments, two groundwater management areas and two irrigation districts within the Harvey Water Irrigation Area.
For the purposes of this report, the region includes water stored in:
- surface water storages
- water held in pipes and infrastructure as part of the urban water supply, wastewater collection, and irrigation water supply systems
- groundwater aquifers.
The region excludes water stored in:
- off-channel water storages and rainwater tanks, such as farm dams and private commercial water storages used to harvest runoff or collect rainwater
- water held in the landscape, such as soil moisture.
For more information regarding items in this water accounting report, please refer to the Water accounting policies.
Land use
The major population centres in the region are:
- Perth metropolitan area (including Rockingham and Kwinana): population 1,806,000; and
- Mandurah: population 91,300 (ABS 2013).
A number of smaller towns are interspersed throughout the rest of the region, including Harvey, Pinjarra, and Gingin.
Figure P4 shows that urban land use is primarily within the Perth metropolitan area (including Rockingham and Mandurah) along the Swan Coastal Plain.
Figure P4 Map of land use in the Perth region
The region also includes two irrigation districts, Harvey and Waroona. These districts are part of the Harvey Water Irrigation Area, which is located on the Swan Coastal Plain near the town of Harvey. The total operating area of these districts is approximately 170 km2 and 55 km2 at Harvey and Waroona respectively. Within these areas, there is currently around 55 km2 and 15 km2 of land in the Harvey and Waroona districts respectively under permanent irrigation for dairy farming, beef grazing, and horticulture.
The irrigation districts are located in the southern area of the region around the town of Harvey and are identified as 'Other intensive uses' in Figure P4.
Other major land uses in the Perth region include:
- conservation and natural environments
- dryland agriculture
- grazing.
Conservation and natural environments are extensive throughout the Perth region and are particularly dominant throughout the Darling Range (to the east of the Darling escarpment). Dryland agriculture occurs across much of the region and grazing is dominant to the east of the Peel–Harvey Estuary below Mandurah (Figure P4).
Table P1 shows the percentage areas of each major land use within the Perth region (Australian Bureau of Agricultural and Resource Economics and Sciences 2010).
Land use |
Area (km2) |
Area (% of total) |
conservation and natural environments |
10,080 |
48 |
dryland agriculture |
6,740 |
32 |
forestry |
587 |
3 |
grazing |
1,178 |
5 |
irrigated agriculture |
235 |
1 |
mining |
3 |
<1 |
other intensive uses |
454 |
2 |
urban |
1,607 |
8 |
water |
272 |
1 |
Total |
21,156 |
Significant aquatic ecosystems
There are a series of significant aquatic ecosystems within the Perth region, primarily located on the Swan Coastal Plain (Figure P5). Many of these systems are part of the groundwater system within the region.
Figure P5 Map of significant wetlands in the Perth region
The sites in Figure P5 are listed in the Directory of Important Wetlands in Australia. There are also three designated Ramsar wetlands within the Perth region:
- Forrestdale and Thomsons lakes
- Peel–Yalgorup wetland system
- Becher Point Wetlands.
The Forrestdale and Thomsons lakes are located in the southern suburbs of Perth. The Peel–Yalgorup wetlands are located around Mandurah and include the Peel–Harvey Estuary and Yalgorup Lake. Both of these systems are major stop-overs for migratory wading birds and important drought refuge areas for waterbirds. The Peel–Yalgorup wetlands also support the largest professional and recreational estuarine fishery in Western Australia.
The Becher Point Wetlands, located near Rockingham in the southern suburbs of Perth, is one of the youngest wetland systems on the Swan Coastal Plain. The sedgelands that occur within the chain of wetland depressions of the site are listed as a threatened ecological community under the Commonwealth Environment Protection and Biodiversity Conservation Act (1999).
Water resources
Water supply in the Perth region is primarily sourced from groundwater aquifers, storages and desalinated water.
Most of the region's water supply comes from groundwater. The groundwater is used for urban water supply as well as individual supply, including for use in agriculture and parks and gardens. There are also an estimated 170,000 residential bores in the Perth metropolitan area (Department of Water 2009a). The important groundwater resources in the region include:
- Gnangara and Jandakot superficial aquifers
- Leederville and Yarragadee confined aquifers
The scope for increased extraction, particularly in the Gnangara system, Perth's largest source of groundwater, is limited.
There are three major surface water resources in the Perth region:
- Swan–Canning river system
- Murray River catchment
- Harvey River catchment.
These surface water resources have been developed to meet the region's water needs. Storages were constructed along tributaries in the upper reaches of these river systems for urban water and irrigation scheme supply. Land clearing for urban and agricultural development has also been extensive throughout these catchment areas. The potential to develop additional storages in the region is limited.
Given that these surface water and groundwater resources are already well developed in the region, alternative water resources, such as seawater desalination and water recycling, are increasingly being used for public water supply. There are two desalination plants in the region, which are now capable of supplying almost half of Perth's urban water requirements.
Surface water
There are three primary river systems within the Perth region:
- Swan–Canning
- Murray
- Harvey.
These rivers generally flow throughout the year; however, most of the flow within these catchments usually occurs during a 3-month period between July and September. The seasonal flow characteristics of the main rivers reflect the rainfall pattern of the region, where most of the rainfall occurs during a 4-month period between May and August (Figure P6).
Figure P7 shows the locations of the most downstream flow gauging stations (and their station number) along these main rivers. Flow data collected at these stations were used to represent the seasonal flow patterns along these rivers in Figure P6. There are other gauging stations along these rivers though they are not shown on this map.
Figure P6 Graph of mean monthly flows along the Swan, Murray, and Harvey rivers and mean monthly rainfall for the Perth region
Figure P7 Location map of key flow gauging stations along the main rivers within the Perth region
Surface water storages are primarily located on various rivers in the Darling Range and are an important water source for both urban water and irrigation scheme supply. The storages, which are managed by the Water Corporation, are shown in Figure P8. The capacity of each storage and its main purpose are shown in Table P2.
Most of the storages within the Perth region are used for urban water supply to the Integrated Water Supply Scheme. Further information on the urban supply storages, including current levels and volumes, is given on the Bureau of Meteorology's Water storage website.
Figure P8 Location map of the surface water storages within the Perth region
The six surface water storages located in the southern part of the region (Figure P8) are used for irrigation water supply to two Harvey Water irrigation districts: Harvey and Waroona (see Table P2). Harvey Water is a private irrigators' cooperative that delivers water to irrigators via a network of pipes and channels from several storages in the region. Harvey Water has a bulk water licence to access a portion of the total capacity.
Storage |
Capacity (ML) |
Dead storage (ML) |
Purpose |
Canning |
90,300 |
60 |
urban supply |
Churchman Brook |
2,200 |
40 |
urban supply |
Drakes Brook1 |
2,300 |
20 |
irrigation supply |
Harvey2 |
55,700 |
780 |
irrigation supply |
Logue Brook3 |
24,200 |
380 |
irrigation supply |
Mundaring4 |
43,000 |
20,560 |
urban supply |
North Dandalup |
73,800 |
1,020 |
urban supply |
Samson Brook5 |
7,900 |
90 |
urban and irrigation supply |
Serpentine |
136,700 |
1,010 |
urban supply |
Serpentine Pipehead |
2,200 |
460 |
urban supply |
South Dandalup |
125,100 |
12,940 |
urban supply |
Stirling6 |
54,300 |
1,800 |
urban and irrigation supply |
Victoria |
9,400 |
50 |
urban supply |
Waroona7 |
14,800 |
170 |
irrigation supply |
Wungong |
56,400 |
3,430 |
urban supply |
Total |
698,300 |
42,810 |
|
4 Primarily supplies water to the Goldfields and Agricultural region located outside of the Perth region boundary.
5–6 Also supplies water to small towns outside of the Perth metropolitan area.
Groundwater
Water table aquifers in the Perth region are also referred to as 'superficial aquifers'. Most groundwater extraction in the Perth region occurs from the Gnangara and Jandakot superficial aquifers (see Figure P9). These aquifers are major sources of water for urban supply as well as individual supply, including for use in agriculture and public parks and gardens.
The Gnangara and Jandakot superficial aquifers are unconfined, multi-layered, complex aquifers that lie west of the Darling escarpment on the Swan Coastal Plain. The sediments of the aquifers range from mostly clay and sand in the east to sand in the centre and sand and limestone in the west along the coast.
The primary underlying aquifers in the Perth region are the Leederville and Yarragadee aquifers. The Leederville aquifer is a multi-layered, confined aquifer that underlies the majority of the Swan Coastal Plain within the region. The only areas of this aquifer that are unconfined are where it immediately underlies the superfical aquifer.
The Leederville aquifer ranges in thickness from 50 metres deep to more than 600 metres deep in the north of the region below the Gnangara superficial aquifer, and from 50–300 metres deep in the middle part of the region below the Jandakot superficial aquifer. It consists of around 50% sandstone and 50% a mix of siltstone and shale. The aquifer is a major source of water for urban water use as well as individual supply.
The Yarragadee aquifer is a multi-layered, confined aquifer that underlies the Leederville aquifer. The base of the aquifer is more than 2,000 metres deep and consists of around 50% sandstone and 50% a mix of siltstone and shale. The aquifer is a major source of water for urban water supply.
The Perth region includes 15 groundwater management areas that all lie on the coastal plain (between the coast and the Darling escarpment). These are proclaimed in the Rights in Water and Irrigation Act 1914 (Western Australia). The proclaimed management areas are managed by the Department of Water (Western Australia) and shown in Figure P9.
Figure P9 Map of groundwater management areas within the Perth region
Desalinated water
Desalinated water for the Perth region comes from two desalination plants:
- Perth Seawater Desalination Plant, located near Kwinana
- Southern Seawater Desalination Plant, located near Binningup in the southern part of the region.
The Perth Seawater Desalination Plant was commissioned by the Water Corporation in 2006. The first stage of the Southern Seawater Desalination Plant was commissioned in September 2011. The second stage of the plant will be fully commissioned in late 2013 and will double the plant's capacity to 100,000 ML per year. The desalinated water supplied to the Integrated Water Supply Scheme from the two plants will meet approximately 50% of Perth's urban water requirements.
For more details on desalinated water in the Perth region, see the Water Corporation website.
Other water resources and systems
The urban water system within the Perth region, also referred to as the Integrated Water Supply Scheme, is operated by the Water Corporation. The system primarily supplies water to the Perth metropolitan area and towns in the southwest area, including Mandurah and Harvey (see Figure P3 in General description). It also supplies water to areas outside the Perth region boundary, including the Goldfields and Agricultural region and Western Australia's southwest region.
Water into the system is sourced from surface water storages and bore fields within the region as well as the desalination plants near Kwinana and Binningup.
For more information on the urban water system in the Perth region, refer to the Water Corporation website.
Two irrigation districts, Waroona and Harvey, are located in the southern area of the Perth region within the Harvey Water Irrigation Area (see Figure P3 in General description). Harvey Water delivers water to irrigators in these districts via a network of pipes and channels from several storages in the region (see Table P2 in Surface water).
For more information on the irrigation scheme, refer to the Harvey Water website.
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
- local irrigation (i.e., parks and recreation grounds) near the treatment plants
- on-site use
- aquifer recharge.
Aquifer recharge has been part of a groundwater replenishment trial conducted in the Perth region since November 2010. Treated wastewater from the Beenyup Wastewater Treatment Plant is further treated to drinking water standards and recharged back into the groundwater store for future use. For more information on the groundwater replenishment trial, see the Water Corporation website.