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National Water Account 2020

Perth: Region description

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.

Perth region map. 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% sourced from groundwater.

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

Geographic information
Water management
Water rights

Geographic information

Perth city from the Swan Brewery (iStock © s_porter01)

General description

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

Map of the main rivers and water catchments. The region is physically defined by mainly 3 surface water catchments: 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

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.

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

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

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.

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 of key gauging stations. Swan River at Walyunga, station number 616011, is in the northern part of the region about 40 km upstream of Perth. Murray River at Baden Powell Water Spout, station number 614006, is on the Darling Range in the region's south. Harvey River at Clifton Park, station number 613052, is 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

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

A graph of mean monthly rainfall and flow volumes for the Perth region. Total flow volumes are derived from streamflow data collected at the most downstream station along the river. Rainfall totals are based on area-averaged data from 1900 to 2020. Streamflow data are based on the following time periods: Swan River (1970–2020), Murray River (1952–2020), and Harvey River (1982–2020).

Numerical values presented in the graph are in the following table. Measurement units are millimetres (mm) for rainfall and megalitres (ML) for flow volumes.

Month	Total rainfall (mm)	Swan River (ML)	Murray River (ML)	Harvey River (ML)
July	156	78,537	71,087	33,251
August	123	90,558	81,797	31,222
September	81.5	43,859	37,394	21,379
October	50.4	13,144	14,634	7,836
November	24.3	3,007	4,477	3,022
December	13.4	661	2,596	1,881
January	12.9	5,374	2,848	1,640
February	15.0	9,801	2,125	1,589
March	19.7	1,679	818	1,793
April	40.3	2,255	1,905	2,078
May	107	6,690	4,889	4,584
June	152	29,757	30,191	17,577

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 of 16 major storages. 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 13 storages, located across most of the region, are all 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

Map showing the locations of major storages within the Perth region. Total capacity of each storage shown in the map is included in the following table.

Geographic location	Storage name	Storage capacity (ML)
North of region, Swan Coast catchment	Mundaring	43,000
	Victoria (Perth)	9,500
	Churchman Brook	2,200
	Canning	90,300
	Wungong	56,400
Centre of region, Murray River catchment	Serpentine Pipehead	2,200
	Serpentine	136,700
	North Dandalup	73,800
	South Dandalup	125,100
South of region, Harvey River catchment	Drakes Brook	2,300
	Waroona	14,800
	Samson Brook	7,900
	Logue Brook	24,200
	Harvey	55,600
	Stirling	55,600
South of region, Collie River catchment	Wellington	184,600

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.

Water management

Whiteman Park, Perth region (Department of Water and Environmental Regulation © Lindsay Preece)

Surface water and groundwater management

Water legislation

The Western Australian Rights in Water and Irrigation Act 1914 establishes the legislative framework for managing and allocating water resources in Western Australia.
The Western Australian Department of Water and Environmental Regulation assists the Minister with functions set out in the Act, including proclaiming water allocation areas, and regulating the taking of water from these areas.

Water allocation areas

Figure R9 Groundwater allocation areas within the Perth region

There are 16 groundwater allocation areas that were proclaimed by the Department of Water and Environmental Regulation in the Perth region.
All groundwater allocation areas lie on the coastal plain between the coast and the Darling escarpment.

Figure R10 Surface water allocation areas within the Perth region

There are 15 surface water allocation areas defined by the Department of Water and Environmental Regulation within the Perth region, covering all of the rivers in the region.

Water management plans

The Department of Water and Environmental Regulation prepares water allocation plans to specify how water resources are to be shared between competing needs in particular areas.
Each plan also recognises its area's environmental values and ensures that sufficient water is retained in the resources to protect water-dependent ecosystems and meet specific social needs.

Table R1 Water allocation plans in the Perth region
Type	Plan Name
Groundwater	Cockburn Groundwater Area Water Management Plan Gnangara Groundwater Areas Allocation Plan Gingin Groundwater Allocation Plan Kemerton Groundwater Subareas Water Management Plan Murray Groundwater Allocation Plan Peel Coastal Groundwater Allocation Plan Rockingham-Stakehill Groundwater Management Plan South West Groundwater Areas Allocation Plan
Surface Water	Gingin Surface Water Allocation Plan Lower Collie Surface Water Allocation Plan Middle Canning River Surface Water Allocation Plan

There are 8 groundwater allocation plans and 3 surface water allocation plans in the Perth region.
All current allocation plans for the Perth region and supporting information can be accessed at the Department of Water and Environmental Regulation website.

Environmental water management

Environmental water legislation

The Environmental Water Provisions Policy for Western Australia guides the Department of Water and Environmental Regulation in planning and decision-making in relation to allocating water to the environment.
The policy describes the role of environmental water regime requirements and environmental water provisions in setting the sustainable diversion limit of a water resource.

Environmental water provisions

Environmental water provisions are specified in water allocation plans.
In surface water management plans, these provisions are often expressed as required flow regimes. Responsibility for achieving these flow regimes is placed on the storage operator and is defined in the licence conditions as part of operating strategies.
In groundwater allocation plans, environmental water provisions are often expressed as minimum groundwater levels at key sites to protect ecological values associated with the groundwater-dependent ecosystems.
Groundwater levels provisions that were first identified in the mid-1980s for the Gnangara water table aquifer and in the early 1990s for the Jandakot water table aquifer, are now ministerial conditions under the Western Australian Environmental Protection Act 1986.
The Department of Water and Environmental Regulation is responsible for monitoring environmental outcomes and enforcing environmental provisions.
Further information regarding environmental water provisions for the 2019–20 year is provided in the Cultural and environmental water note in 'Supporting information'.

Cultural water management

The waterways and groundwater systems within the Perth region are important to cultural beliefs of the Nyungar people.
Cultural and social values of the rivers and groundwater-dependent features in the region are considered through environmental water provisions in the allocation plans.

Organisations responsible for water management

Organisations responsible for water supply and management in the Perth region shown below.

Table R2 Water utilities and other organisations in the Perth region
Organisation	Responsibility
Department of Water and Environmental Regulation	water resource planning managing and allocating water resources managing water use policy advice to government
Harvey Water	irrigation water supply
Water Corporation	infrastructure operator urban water supply wastewater services operate all major surface water storages

Water rights

Joondalup Lake, Perth region (Department of Water and Environmental Regulation © Lindsay Preece)

Operating rules and constraints

Control of water abstraction within the Perth region is exercised by the Department of Water and Environmental Regulation through allocation planning and licensing.
In January 2016, a policy was implemented requiring all licensees to have approved meters and to report the amount of water abstracted to the department (Department of Water 2016). The policy is being implemented in a staged approach over 5 years from 1 February 2016.
The Water Corporation manages the bore fields and surface water storages within the Perth region for urban water supply. As part of its licence conditions, the Water Corporation is required to comply with operational strategies and report on environmental impacts.
The Department of Water and Environmental Regulation manages all water restrictions, including domestic garden bore use. Further information can be found on the Department of Water and Environmental Regulation website.

Water entitlements and other statutory water rights

Under the Western Australian Rights in Water and Irrigation Act 1914 a licence is required to abstract water in proclaimed surface water and groundwater areas. The Act also requires all artesian bores to be licensed for their construction and the abstraction of water.
Licences to abstract water are administered by the Department of Water and Environmental Regulation. Licences usually specify the conditions, length of tenure, and the maximum volume of water that may be abstracted. This volume is referred to as the water entitlement.
The Department of Water and Environmental Regulation conducts assessments to ensure licensees comply with licence conditions.
The Act has provisions for water abstraction under a riparian right, which is a right to abstract water for specific uses attached to land ownership (e.g. stock and domestic use).
A licence to abstract water is not required for the following groundwater uses: fire-fighting; non-intensive stock use; domestic garden and lawn irrigation (not exceeding 0.2 hectares); and short-term dewatering activities where small volumes of water are abstracted from the water table aquifer (usually for building construction).

Harvey Water Irrigation Scheme

Harvey Water holds a bulk water licence to abstract water that is stored in surface water reservoirs owned by the Water Corporation.
Harvey Water's legal right to bulk water is transferred to owners who have an equity entitlement to water via their shareholding in the Harvey Water Irrigation Cooperative.
Members of the Harvey Water Irrigation Scheme hold shares in the cooperative and a corresponding certificate of water entitlement that is proportional to their shareholding.

Water allocations

The Department of Water and Environmental Regulation issues licences that specify a maximum volume of water that may be abstracted.
Unless restrictions are announced, water may be abstracted up to the maximum volume specified on the licence, that is, water allocations are generally assumed to equal 100% of the annual water entitlement.
For irrigation scheme supply, Harvey Water considers the status of the irrigation supply storages to determine the allocation under Harvey Water's bulk water entitlement. Water is then made available to individual members of the Harvey Water Irrigation Cooperative under the conditions set out in its rules.

Trades and water rights transfers

The Rights in Water and Irrigation Act 1914 permits the trading or transferring of licences, but only within the same water management area, and subject to compliance with the other conditions of the Act and allocation plans.
Water allocation plans include rules for trading such as limitations on trading to within allocation subareas or between particular subareas, and limitations on trading of entitlements which have not been used (sleeper licences).
Members of the Harvey Water Irrigation Cooperative can trade their water allocations in accordance with the cooperative's rules, provided both parties are members of the cooperative. Members are prevented from trading water directly with parties outside the cooperative. For more details, please refer to the Harvey Water website.

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