Perth

Water legislation

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, except as appropriate under a written law.

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
• regulate the taking of water from prescribed water management areas.

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 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
• Jandakot drainage and water management plan, Peel main drain catchment
• Rockingham-Stakehill groundwater management plan
• Gnangara groundwater areas allocation plan
• Gingin surface water allocation plan
• Lower Canning River surface water allocation plan
• Murray groundwater allocation plan

Environmental water legislation

The Environmental Water Provisions Policy for Western Australia (Water and Rivers Commission, 2000) guides the Department of Water’s water allocation planning and decision-making in relation to allocating water to the environment. The policy describes the role of ecological water requirements and environmental water provisions in setting the sustainable diversion limit of a water resource.

Environmental water provisions

Surface water

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 ecological water 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 ecological water requirements as part of the development of surface water management plans. For example, in the Gingin surface water allocation plan (Department of Water, 2009a), the minimum flows for gauging stations within the area were based on preliminary ecological water requirements developed by Storey and Davies (2002). In the Lower Canning River surface water allocation plan (Department of Water, 2010), ecological water requirements were developed by Radin et al. (2010). 

Groundwater

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 Criteria under the Environmental Protection Act 1986.

When environmental monitoring indicates that 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.

The organisations responsible for water supply and management in the Perth region are listed in Table A1.