Australian Natural Resources Atlas

Natural Resource Topics

Water resources - Overview - Western Australia


Location Map of WANo photo caption available

Western Australia

Western Australia water resources - at a glance

On average Western Australia uses 1796 GL of water per year, which is 7% of Australia's total use. Of the total water use, 658 GL of water is used from surface water sources and 855 GL of surface water is allocated to consumptive use.

1138 GL of water is used from groundwater sources. The sustainable yield of groundwater for Western Australia is 6304 GL per year which is 22% of Australia's total.

None of the 44 Surface Water Management Areas and 44 of the 174 groundwater management units are assessed as being highly or overdeveloped.

Map of Western Australia's surface water management areas

Select a surface water management area on the map to find out more about that area.

Map of Western Australia's surface water management areas
Map of Western Australia's groundwater provinces

Select a groundwater province on the map to find out more about that area.

Map of Western Australia's Groundwater Provinces

Overview

The State of Western Australia occupies one third of the continent but it is inhabited by less than one tenth of the population. The water resource management regime is therefore one of: large scale; diverse hydroclimate; development situations ranging through large areas of wilderness, pastoralism, large scale mining development, broad-acre farming, coastal pockets of intensive irrigation, and the intensive development of the Perth Coastal Plain, where some 85% of the population resides.

Physiographically, the ancient hard-rock provinces of the Western Plateau and Pilbara regions dominate the State. These ancient plateaux are flanked on the west coast by the younger Perth and Carnarvon sedimentary basins, and in the eastern deserts by the Eucla, Officer and Canning sedimentary basins. At the north lies the Kimberley Plateau a hard-rock province with well-incised river systems. Drainage of the interior of the Western Plateau and desert basins is internal and poorly defined, but well defined and significant river systems drain to the coast from the southern and western perimeter of the plateaux.

The hydroclimate varies from the tropical monsoon region in the north; through an erratic, semi-arid climate of the northwest and interior; to temperate, winter rainfall regions of the south. Most rivers in Western Australia are intermittent, with summer flow in the north, winter flow in the south and ephemeral river flows in the northwest. Perennial streams are a comparatively unfamiliar feature. Substantial quantities of confined and unconfined groundwater of varying quality occur in the sedimentary provinces. In the hard-rock provinces groundwater occurs in lesser but valuable quantities in fractured rocks and superficial river alluvium.

Water has been vital to the population and growth of the State. Spread of population in the hinterlands has been dependent largely on underground water or extensive piped reticulation systems from coastal sources. The environment has dictated strong reliance on public water systems and on major dams for effective utilisation of surface water. Urban & industrial use exceed irrigation use across the State, in strong contrast to the eastern seaboard, but significant public irrigation systems have been developed in the South West and Timor Sea Divisions. Intensified self-supplied utilisation of water has been a comparatively recent trend in the State associated with irrigation, urban and industrial developments of underground and surface water. Although many centres enjoy relatively high per-capita use of water, Western Australian rural and urban communities are responsive to calls for efficient water use.

State development has also extracted a price in water values, particularly in extensive salinisation of larger rivers of the southwest, the catchments of which extend beyond the forests to agricultural areas created by removing native woodlands. In the south west, the forested escarpment at the west of the plateau has been a focal point of dam development and, on the coastal plain, the inter-action of major unconfined groundwater sources and coastal wetlands has led to relatively advanced consideration of environmental management in groundwater development.

In recent years, State and National governments have introduced a suite of national water reforms with one of the primary objectives being sustainable development of water resources.

A basic requirement of sustainable development and the reform agenda is a well managed system of water allocation which supports orderly development, avoids over-use, and reflects community goals for maintaining environmental quality and diversity.

Australia's and Western Australia's water resources are in varying levels of development and management. The scope and complexity of management needed for sustainable development of a particular resource depend on its level of utilisation, demand growth, the resource's values and its management objectives. Current resource utilisation in WA's water economy is generally low enough to allow allocation planning and a comprehensive allocation system to pursue sustainable development under a precautionary progression to full allocation. In pursuing this opportunity a wider range of measures are available and appropriate than in a more heavily developed water economy.

This audit is designed to support appropriate and timely water allocation and use. The audit also provides a basis for discussion and planning of future economic development, and for assisting in development of planning processes to define and protect social and environmental water allocations.

For the purposes of this audit, the study has necessarily made working assumptions for many resources where demand has not yet led to specific investigation or to public determination of management objectives and environmental allocations. It is important to understand that such assumptions are not prescriptive. The result of the audit work is a review, not a plan. However, the audit does provide an analytical framework and process which assists practical application of precautionary principles in management of water allocation.

Surface Water Reporting Units

The Audit has been careful to ensure an underlying consistency and comparability with Review85, the last major water-resource audit. Data have been compiled under consistent definitions, recognised potential development locations, River Basins, Regions and Drainage Divisions to Review85. It is therefore possible to recognise where significant differences occur for reasons such as improved hydrology, revised climate definitions or anticipation of environmental requirements.

For this audit 44 surface water management areas have been adopted as the reporting unit for WA. These surface water management areas coincide with the Australian Water Resources Council (AWRC) basins. To provide a high level of summary across the State, the basin level results have been aggregated into four Drainage Divisions, namely the South West, Indian Ocean, Timor Sea and Western Plateau.

Groundwater Reporting Units

Groundwater management units (GMUs) have been defined by the Water and Rivers Commission and preceding organisations (Public Works Department, Metropolitan Water Authority and Water Corporation) which have had responsibility for groundwater regulation. They are statutory areas declared under the Metropolitan Water Supply Sewerage and Drainage Act and the Rights in Water Irrigation Act.

The boundaries to the GMUs follow cadastral boundaries or boundaries defined by latitude and longitude, which cover all of the State except the area bordering the southern coast, and in the south western part of the State. The GMUs have been erected for various reasons such as protection of town water supplies and to enable legislative control of groundwater in response to various development pressures. Some of the GMUs, particularly in the Perth Basin, have been further subdivided into groundwater management sub-areas to meet local groundwater management requirements. As a result, most of the GMUs do not closely correspond with the groundwater provinces or natural physiographic regions.

An unincorporated area (UA) is an area not included within a GMU. About 12% of Western Australia along the south coast and south-western part of the State is a UA in which a number of small GMUs around town water supplies (eg. Bremer, Albany and Bolgart) are located.

For the purposes of the Audit, the term Groundwater Management Unit (GMU) was applied to a discrete aquifer, or part of an aquifer within a GMU or UA. In the sedimentary basins where aquifers may be superimposed on each other, or the aquifer extends into several GMUs, each aquifer or part of an aquifer is dealt with as a separate GMU. For the purpose of the Audit, the UA was split into seven GMUs (W2-4, W9, W12, W34 and W171) corresponding with their respective groundwater provinces.

For the Audit all known major aquifers currently being exploited or considered likely to be exploited in the foreseeable future were identified in each GMU and their extent determined from the State Geological or Hydrogeological maps. The resultant GMUs were superimposed on a composite map showing groundwater provinces and groundwater management areas and numbered consecutively, commencing around the coast from the South Australian border and then through the central part of the State. Three GMUs not identified initially but subsequently recognised were added to the end of the list. 174 GMUs ranging from 1 km2 (Dwellingup) to 312,250 km2 (Canning) including seven in UA were recognised. The GMUs were also given names that reflect the geographic region, the geographic region and aquifer, or town water supply.

For further information, contact the Western Australian Department of Environment at www.environment.wa.gov.au.

Further Information

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