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National Water Account 2016

Perth: Water access and use

Groundwater allocations increased from the previous year due to recent dry conditions across the region reducing surface water availability. Approximately 50% of the region's water entitlements were for the urban water system; more than 40% were for individual users, primarily for agricultural purposes.

 

  

Water rights, entitlements, allocations and restrictions

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

Introduction

This note provides information about the water access rights granted by jurisdictions to the users of the region's water resources and the associated allocation announcements and abstractions.

The 2016 Account acknowledges that the legislative water resource management frameworks relating to Australian water rights vary greatly across jurisdictions, sometimes making comparisons difficult. To facilitate meaningful comparisons between the 2016 water accounting reports, the Bureau of Meteorology has developed and applied an accounting concept to classify and report water entitlements within a water asset/water liability framework.

According to that framework, water rights for the Perth region for the 2015–16 year have been classified as shown below.

 

Surface water rights

Surface water rights in the Perth region during the 2015–16 year refer to surface water supply for:

  • individual users—38,842 ML
  • urban water system—247,950 ML
  • irrigation scheme—68,360 ML.

Surface water rights for the urban water system and the irrigation scheme relate to entitlements to divert water from storages to the Perth region's Integrated Water Supply Scheme and the Harvey Water Irrigation Area, respectively.

In the Perth region, surface water allocations for individual users and the urban water system are equal to 100% of the water access entitlement; however, allocations for the irrigation scheme are a percentage of the entitlement, which are announced at the start of the irrigation season on 1 October each year.

The volume of surface water entitlements, corresponding allocations, and diversions for the 2015–16 year compared with the previous 4 years are shown in Figure S13. The percentage shows the ratio of diversion to the allocation announcement.

 

Figure S13  Graph of surface water access entitlements, allocations and diversions in the Perth region for the years ending 30 June 2012 to 2016
Figure S13 Surface water access entitlements, allocations and diversions in the Perth region for the years ending 30 June, from 2012–2016

 

Allocations for surface water diversion to the urban water system remain unchanged from the previous year; however, diversions to the urban water system decreased by approximately 15% from last year (Figure S13). Surface water diversion to the urban water system is a gross volume; that is, a portion of this water is made up of groundwater and desalinated water produced in the winter and then transferred to storages for future use. Net surface water diversion to the urban water system during the 2015–16 year (20,100 ML) decreased by more than 50% from previous years (see Urban water system note).

Allocations and diversions for both individual users and the irrigation scheme during the 2015–16 year were similar to the previous year. The relatively high percentage of diversion to allocation for individual users is because the majority of individual licence holders abstractions were not measured and were assumed equal to the licence holders' allocations.

There were approximately 200 individual users that primarily sourced water from rivers within the region for mining and industrial purposes. The water supply licences are divided into licence entitlement purposes (Figure S14).

 

Figure S14  Graph of surface water allocation to individual users for each licence purpose
Figure S14 Surface water allocation to individual users for each licence purpose

 

Groundwater rights

Groundwater rights in the Perth region during the 2015–16 year refer to groundwater supply for:

  • individual users—306,671 ML
  • urban water system—160,938 ML.

Groundwater rights for the urban water system relate to entitlements to extract water from aquifers to supply to the Perth region's Integrated Water Supply Scheme.

The volumes of groundwater allocation and extraction for the 2015–16 year compared with the previous 4 years are shown in Figure S15. The percentage shows the ratio of extraction to the allocation announcement. Non-allocated extractions from domestic non-licensed bores within the region (80,845 ML) is also shown in Figure S15.

 

Figure S15  Graph of groundwater allocations and extractions in the Perth region for the years ending 30 June 2012 to 2016
Figure S15 Groundwater allocations and extractions in the Perth region for the years ending 30 June, from 2012–2016

 

Groundwater allocations and extractions for urban supply had decreased over the last 5 years with increasing desalinated water production; however, groundwater allocation was increased in the 2015–16 year due to the limited availability of surface water (Figure S15). Similarly, extractions to the urban water system also increased from the previous year.

Groundwater allocations for individual users during the 2015–16 year also increased from the previous year. The relatively high percentage of extraction to allocation for individual users is because the majority of individual licence holders abstractions were not measured and were assumed equal to the licence holders' allocations.

There were approximately 6,000 individual users that sourced water from aquifers within the region. The water supply licences are divided into licence entitlement purposes (Figure S16).

 

Figure S16  Graph of groundwater allocation to individual users for each licence purpose
Figure S16 Groundwater allocation to individual users for each licence purpose

 

Water restrictions

During the 2015–16 year, urban-water users and garden-bore users were on a sprinkler roster.

Whilst on the sprinkler roster, urban-water users who were connected to the Perth region's Integrated Water Supply Scheme were able to use their sprinklers 2 days per week. Residents with their own garden bore had an additional sprinkler day per week. The sprinkler days were determined by the last digit of the user's street number and sprinklers needed to be used before 9am and after 6pm. There was a total sprinkler ban for the winter months (June–August).

These water restrictions have been in place in the region since November 2010. For more information, refer to the Bureau of Meteorology's Water restriction website.

 

Water market activity

Perth city. Source: istock © s_porter01

In Western Australia, water entitlement trades and transfers can only occur within the same water management area (see the Trades and water rights transfers section in the 'Region description').

Trades and transfers are defined as water entitlements that are permanently transferred to another licence holder. A trade is where the new licence holder will abstract water from a different location; a transfer is where water abstraction will occur from the same location. An agreement is a temporary transfer of a licence water entitlement to another licence holder (also referred to as a temporary transaction). More information on water entitlement transactions can be found on the Department of Water website.

Trades and transfers of licence entitlements that occurred in the Perth region during the 2015–16 year are provided in Table S9. Most of the water market activity within the Perth region during the year was related to groundwater entitlement trade.

 

Table S9 Water trade in the Perth region during the 2015–16 year
Transaction typeNumber of licencesVolume
(ML)
Surface water entitlement transactions  
Transfer277
Groundwater entitlement transactions  
Trade4212
Transfer88132
Agreement2361
Total155282

 

Water use

Goldfields pipeline, Perth region. Source: Water Corporation © Darryl Peroni

Economic, social and cultural benefit

Surface water and groundwater resources within the Perth region are used for public water supply and irrigation scheme supply, as well as private water supply for purposes such as agriculture, industry, and mining. For a summary of the water volumes allocated for various economic purposes within the region, including the actual volumes abstracted, refer to Surface water rights and Groundwater rights above.

Water is released from Harvey Reservoir during the irrigation season (generally November–May) to ensure that there is flow along Harvey River downstream of the reservoir. Along with irrigation supply and environmental requirements, it is considered important that Harvey River has flow for aesthetic reasons, primarily because this region of the Harvey River is a tourist precinct.

Water regimes required to support cultural values are not quantitatively defined in allocation plans (see the Cultural water management section of the 'Region description'); however, the cultural values are considered within the environmental water provisions.

 

Environmental benefit

Introduction

Water for environmental benefit in the Perth region is provided according to two different environmental water management scenarios:

  • planned, partly regulated surface water
  • planned groundwater.

 

Planned, partly regulated surface water

The dominant feature of environmental water management in this scenario is the ability to control or influence flow by operational releases from storages. For the Perth region, these environmental water releases are also referred to as riparian releases.

Environmental water legislation

Environmental water provisions in the Perth region are defined for the Canning River. These provisions are outlined in the Middle Canning River Surface Water Allocation Plan.

The plan outlines a flow regime required to maintain current ecological conditions in the lower Canning River. These ecological requirements were developed by Radin et al. (2010), and include the maintenance of:

  • flow connectivity
  • pool depth as refuge habitat
  • a minimum flow over riffles for macro-invertebrates
  • prevention of anoxic conditions in pools.

Environmental water provisions

Environmental water releases are made during the drier months between November and May from surface water storages and water mains along the Canning River. There are six release points along the river, and these releases make up most of the river's summer baseflow. The location of these release points are given in Figure S17 and in Chapter 5 of the Middle Canning River Surface Water Allocation Plan.

The Water Corporation operates the storages and manages the release of water from the environmental release points. The Department of Water monitors the flow along the Canning River at the Seaforth gauging station (Station 616027: see Figure S17) to ensure that adequate baseflow is being maintained.

 

Figure S17  Map of middle Canning River environmental release points
Figure S17 Middle Canning River environmental release points

 

Figure S18 shows the required flow regime at the Seaforth gauging station (Station 616027) throughout the standard summer-flow release period. The release schedule commences when flow at the Seaforth station falls below 9.3 ML/day for 3 consecutive days in late spring. Once started, the releases must meet the required flow threshold; that is, the minimum daily flow measurement at the Seaforth gauging station must remain above 1.8 ML/day during the summer period. Releases are ceased when 40 mm of rainfall are recorded after 1 April at the Bureau of Meteorology's Gosnells weather station.

 

Figure S18 Example water provisions for the Canning River; required baseflows and higher flow pulses are also shown
Figure S18 Example water provisions for the Canning River; required baseflows and higher flow pulses are also shown
 

 

In addition, there is also provision for up to three higher volume 'pulse' flows to aid upstream fish migration during summer. These pulse flows are scheduled to occur between November and January and are generally initiated when flow at the Seaforth gauging station (Figure S17) is less than 9.3 ML/day for 15 consecutive days.

A more detailed description of these environmental water release schedules are provided in appendices A and B of the Middle Canning River Surface Water Allocation Plan, including variations to the release schedule for low-rainfall years.

Environmental water outcomes

The mean daily flow at the Seaforth gauging station along the Canning River during the summer period for the 2015–16 year is shown in Figure S19.

 

Figure S19 Daily flow in the Canning River compared with the required flow regime during the 2015–16 year
Figure S19 Daily flow in the Canning River compared with the required flow regime during the 2015–16 year

 

The release schedule for the Canning River commenced early-October 2015 after 3 consecutive days of less than 9.3 ML/day of flow was observed at the Seaforth station (Figure S19). The release schedule ceased on 26 April 2016 when cumulative rainfall (since 1 April) at Gosnells weather station exceeded 40 mm.

During the winter months (May–September 2015), rainfall at Bickley station (Bureau of Meteorology Station 9240) was less than 675 mm, which triggered the adoption of the low-rainfall release schedule. Under this scenario, releases into the Canning River are reduced to approximately 75% of the standard release schedule (see Figure S18) and pulse flows are ceased. More information on the low-rainfall release schedule is provided in Appendix B of the Middle Canning River Surface Water Allocation Plan.

 

Planned groundwater

In the Perth region, limiting the groundwater extractions is the main instrument used to meet the requirements of the groundwater-dependent ecosystems. The Department of Water considers the water requirements of groundwater-dependent ecosystems when setting limits to groundwater extractions in the allocation planning process.

Environmental water legislation

Environmental water provisions in the Perth region are currently defined for the Gnangara and Jandakot groundwater systems. These provisions are now ministerial guidelines under the Western Australian Environmental Protection Act 1986 and are based on water level criteria set for representative sites in the area. The Department of Water monitors these sites to determine compliance with criteria; however, no information about the environmental water outcomes was available to be included in this report.