Surface water and groundwater
The Rights in Water and Irrigation Act 1914 establishes the legislative framework for managing and allocating water resources in Western Australia. Under the Act, the right to the use, flow and control of the water in watercourses, wetlands and underground water sources is vested in the Crown.
The Department of Water assists the Minister with the water resource management powers and functions set out in the Act, including the power to:
- proclaim water management areas across the State for surface water and groundwater; and
- regulate the abstraction of water from prescribed water management areas, including through the issuing of licences and the announcements of restrictions on licence use.
Water management plans
The Department of Water prepares water management plans to specify how water resources are to be shared between competing needs in particular areas. Management plans establish sustainable diversion limits for certain water resources and define the water available for use. The limits are established to ensure that sufficient water is retained in the water resource to protect water-dependent ecosystems and to meet specific social needs.
Water management plans and water allocation plans in place within the Perth region include:
- Cockburn Groundwater Area Water Management Plan
- Gnangara Groundwater Areas Allocation Plan
- Gingin Surface Water Allocation Plan
- Middle Canning River Surface Water Allocation Plan
- Murray Groundwater Allocation Plan.
All current allocation plans for the Perth region, and supporting information, can be accessed at the Department of Water website.
Environmental water management
Environmental water legislation
The Environmental Water Provisions Policy for Western Australia guides the Department of Water in water allocation 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 specified in the surface water management plans are expressed as a minimum flow at key gauging stations within the management area. This minimum flow (measured in ML/day) is the daily water regime requirement for the stream. The Department of Water monitors flows at each of these key gauging stations to ensure minimum flows are maintained.
Studies are conducted to determine these water regime requirements as part of the development of surface water management plans. For example, in the Gingin Surface Water Allocation Plan, the minimum flows for gauging stations within the area were based on preliminary water regime requirements developed by Storey and Davies (2002). In the Middle Canning River Surface Water Allocation Plan, water regime requirements were developed by Radin et al. (2010).
Environmental water provisions specified in the water management plans are expressed as minimum groundwater levels within the management area. These minimum levels are maintained for the purposes of protecting key ecological values associated with the groundwater-dependent ecosystems. These provisions, which 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 Guidelines under the Environmental Protection Act 1986.
When environmental monitoring indicates there is a threat to the ecological health of a groundwater-dependent ecosystem, remedial action can be taken by the Department of Water, in conjunction with other organisations, for the best management of the ecosystem (e.g. announce a restriction on water extraction to particular users).
Organisations responsible for water management
The organisations responsible for water supply and management in the Perth region are listed in Table A1.
Storages operated within the region
All major surface water storages (see Table P2 in Physical information)