Perth
Water access and use

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, diversions, adjustments and forfeitures.

The 2013 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 water accounting reports included in the 2013 Account, 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 2012–13 year have been classified as shown in tables 1 and 2.

Table 1 summarises the surface water rights for the Perth region, including surface water allocations, abstractions, adjustments and forfeitures during the 2012–13 year.

Note that water allocations (line items 21.2 Surface water allocation announcements – urban water system and 21.3 Surface water allocation announcements – irrigation scheme), abstractions (line items 17.12 Entitled diversion of allocated surface water to urban water system and 17.13 Entitled diversion of allocated surface water to irrigation scheme) and adjustments and forfeitures (line items 13.2 Adjustment and forfeiture of surface water allocation – urban water system and 13.3 Adjustment and forfeiture of surface water allocation – irrigation scheme) shown in italics in Table 1 relate to surface water entitlements to the urban water system and irrigation schemes respectively. These line items appear in the Surface water section of the 'Water resources and systems' note; however, they do not appear in the water accounting statements because they are transactions that occurred within the region. These transactions did not impact the region's total water assets and water liabilities.

The actual abstraction of allocated water during the 2012–13 year compared to the 2011–12 year is shown in Figure 1. The percentage shows the ratio of actual water abstraction to allocation announcements.

Figure 1  Comparsion of surface water allocations and abstractions in the 2012–13 year to the 2011–12 year

Figure 1 shows that the allocation announcements for surface water diversion to individual users and the urban water system during the 2012–13 year increased from the previous year. The volume of surface water abstracted during the year also increased. The allocation announcement for water diversion to the irrigation scheme, as well as actual abstraction during the 2012–13 year, slightly decreased from the previous year.

More information about the items presented in Table 1 is provided in the linked line item notes.

Table 2 summarises the groundwater rights for the Perth region, including groundwater allocations, abstractions, adjustments and forfeitures during the 2012–13 year.

The total water allocation announcement is assumed to equal 100% of the annual entitlement.

Note that water allocations (line item 22.2 Groundwater allocation announcements – urban water system), abstractions (line item 18.12 Entitled extraction of allocated groundwater to urban water system) and adjustments and forfeitures (line item 14.2 Adjustment and forfeiture of groundwater allocation – urban water system) shown in italics in Table 2 relate to groundwater entitlements to the urban water system. These line items appear in the Groundwater section of the 'Water resources and systems' note; however, they do not appear in the water accounting statements because they are transactions that occurred within the region. These transactions did not impact the region's total water assets and water liabilities.

The actual abstraction of allocated water during the 2012–13 year compared to the 2011–12 year is shown in Figure 2. The percentage shows the ratio of actual water abstraction to allocation announcements.

Figure 2  Comparsion of groundwater allocations and abstractions in the 2012–13 year to the 2011–12 year

Figure 2 shows that the allocation announcements for groundwater extraction to individual users and the urban water system during the 2012–13 year decreased from the previous year. The volume of groundwater abstracted during the year also decreased.

More information about the items presented in Table 2 is provided in the linked line item notes.

During the 2012–13 year, urban-water users and garden-bore users were on a sprinkler roster.

Whilst on the sprinkler roster, urban-water users connected to the Intergrated Water Supply Scheme in the Perth region can use their sprinklers two days per week. Residents with their own garden bore have an additonal sprinkler day per week. The sprinkler days are determined by the last digit of the user's street number and sprinklers must be used before 9am and after 6pm. There is a total sprinkler ban for the winter months (June–August).

Table 3 shows the trades and transfers of licence entitlements that occurred in the Perth region during the 2012–13 year. All of these entitlement transfers occurred within the same surface water or groundwater management area (see the Trades and water rights transfers section in the 'Contextual information').

In Western Australia, 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 Western Australian Department of Water website.

The Harvey Water Irrigation Cooperative can trade water with the Water Corporation (see Water market rules: inter-valley and within-valley trading section in the 'Contextual information'). Most of the water market activity within the Perth region during the 2012–13 year was related to surface water entitlement trade between these two organisations (32,260 ML). 

Surface water and groundwater resources within the Perth region are used for public water supply, 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 line items 32.3 Surface water access entitlement for allocated diversions and 33.3 Groundwater access entitlement for allocated extractions.

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. 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 'Contextual information'); however, the cultural values are considered within the environmental water provisions.

Water for environmental benefit in the Perth region is provided according to two different environmental water management scenarios: planned, partly regulated surface water; and planned groundwater.

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 currently only 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 releases are also made from other rivers and storages in the region (e.g., Serpentine River and Wungong Brook) but there are no statutory requirements associated with these releases.

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 comprise most the river's summer baseflow. The location of these release points are given 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 line item 17.2 River outflow from the region for location) to ensure that adequate baseflow is being maintained.

Figure 1 shows the required flow regime at the Seaforth station throughout the standard summer-flow release period. The release schedule commences when flow at the Seaforth station falls below 9.3 ML/day for three 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's Gosnells weather station.

Figure 1  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 is less than 9.3 ML/day for 15 consecutive days (Figure 1).

A more detailed description of these environmental water release schedules are provided in Appendix 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 2012–13 year is shown in Figure 2.

Figure 2 Graph of the daily flow in the Canning River compared with the required flow regime during the 2012–13 year

The summer-flow release schedule for the Canning River commenced in mid-October after three consecutive days of less than 9.3 ML/day of flow was observed at the Seaforth station (Figure 2). There were also three high volume pulse flows observed in the river during November–December 2012. The release schedule ceased on 2 May 2013 when cumulative rainfall (since 1 April) at Gosnells weather station exceeded 40 mm.

Figure 2 also shows that flow in the Canning River exceeded the minimum baseflow requirements for the majority of the summer period except for five occasions during February 2013. On four of these occasions, flow fell below the threshold for only one day. On one occasion, flow was below the threshold for four days (11–14 February 2013); however, the trigger for action by the department is when daily flow at the Seaforth station falls below 1.8 ML/day for five consecutive days.

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 consider 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 monitors these sites to determine compliance with criteria; however, no information about the environmental water outcomes was available to be included in this report.