Water resources - Availability - Western Australia
Western Australia
Western Australia 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/.
How much surface water does Western Australia have?
Hydrology
For the South West Drainage Division, where streamflow data and hydrologic analyses are relatively accurate and have a sufficient time base, the basic parameters of mean annual flow (6790 GL/yr) and technically divertible flow (2940 GL/yr) are very closely consistent with the assessments of Review85. The extreme climate perturbation of the last 25 years in the South West Division (virtual absence of years wetter than average) was taken into account when producing these assessments for the Audit.
By comparison, in the north of the State, where streamflow data and hydrological analysis have advanced in the intervening period, but still remain less accurate than for the South West, there are some notable differences from Review85.
For the Timor Sea Division, largely due to streamflow data updates, the assessed mean annual river flows (3300 GL/yr) and divertible yields (11300 GL/yr) are some 10% and 30% above those of Review85.
For the Indian Ocean Division, the situation is more complex. Stream flow assessments have increased the estimated mean annual flows by around 16 % to 4610 GL/yr. However, reappraisal of the hydrology of reservoirs in the region, involving re-assessments of flow variability, salinity and evaporation as inputs to model simulation, has demonstrated that technically feasible yields can be reliably achieved without dependence on conjunctive use, although conjunctive use can significantly improve the yield outcomes. Estimates of divertible yields for this Division totalling 740 GL/yr are some 2.5 times the magnitude of the very conservative figures used in Review85 where surface water potential was seen to be heavily constrained by the availability of aquifers suitable for conjunctive use. Although considered a significant improvement over Review85, the Audit figures for the Indian Ocean Division's resources are still only rated as reconnaissance level assessments. Divertible yields, as used in the Audit, are essentially independent reservoir analyses interpreted as being made more secure by conjunctive use availability.
The estimated mean annual stream flow within the Western Plateau is zero, with a nominal 1 GL/yr for divertible yield.
Sustainable Yield
Sustainable yield determinations for any particular resource cannot be made before the investigations and public processes, by which they are set, take place. However, the figures used in the Audit have sought to establish realistic imitations of the process outcomes at Regional and Divisional level and to set useful precautionary check limits at more detailed levels.
The resulting figures anticipate very considerable proportions of the Mean Annual Flow and Divertible Yield will be reserved as environmental allocations. Across the State as a whole the Audit anticipates that almost two thirds of divertible yield will be foregone for environmental allocations ranging from 40% foregone in the Indian Ocean Division to almost three quarters in the Timor Sea Division. The total sustainable yield for the State is estimated as 5210 GL/yr, of which 4880 GL/yr is fresh/marginal. This is about 12% of total Mean Annual Flow.
In the South West Division, the most highly developed region of the State, the Audit calculations result in a balance whereby sustainable yield of fresh-marginal resources totalling 1610 GL/yr is limited to around 55% of divertible yield or 24 % of Mean Annual Flow.
In the Timor Sea Division, the effects of environmental and cultural constraints on development potential, through regional planning in particular and allocation processes generally, are seen to be even more significant than for the South West. Most of the State's wild rivers are located in the Kimberleys. The Audit anticipates that less than 3160 GL/yr will be realised as sustainable yield in this Division, which is about 30% of divertible yield, or about 10% of Mean Annual Flow.
In the Indian Ocean Division about 60 % of divertible yield has been assigned to sustainable yield totalling 440 GL/yr. However, because of flow variability, the sustainable yield is as low as 10% of Mean Annual Flow.
The sustainable yield for the Western Plateau Division has been estimated as a nominal 1 GL/yr.
| Basin/Surface Water Management Area | Mean Annual Run-off (GL/yr) | % of state | Natural mean annual out-flow (GL/yr) | In-flow (GL/yr) |
|---|---|---|---|---|
| Albany Coast | 330 | .77 | 326 | 0 |
| Ashburton River | 680 | 1.58 | 540 | 0 |
| Avon River | 179 | .41 | 279 | 0 |
| Blackwood River | 1,046 | 2.43 | 1,032 | 0 |
| Busselton Coast | 599 | 1.39 | 592 | 0 |
| Cape Leveque Coast | 450 | 1.04 | 450 | 0 |
| Collie River | 340 | .79 | 248 | 0 |
| De Grey River | 1,148 | 2.66 | 850 | 0 |
| Denmark River | 210 | .49 | 209 | 0 |
| Donnelly River | 331 | .77 | 322 | 0 |
| Drysdale River | 3,000 | 6.96 | 3,000 | 0 |
| Esperance Coast | 136 | .32 | 136 | 0 |
| Fitzroy River (WA) | 9,200 | 21.33 | 9,199 | 0 |
| Fortescue River | 221 | .51 | 280 | 0 |
| Frankland River | 205 | .47 | 204 | 0 |
| Gascoyne River | 646 | 1.5 | 646 | 0 |
| Greenough River | 67 | .16 | 65 | 0 |
| Harvey River | 215 | .5 | 125 | 0 |
| Isdell River | 3,100 | 7.19 | 3,100 | 0 |
| Keep River (WA) | 590 | 1.37 | 210 | 0 |
| Kent River | 170 | .39 | 169 | 0 |
| King Edward River | 3,260 | 7.56 | 3,260 | 0 |
| Lennard River | 1,710 | 3.96 | 1,710 | 0 |
| Lyndon-Minilya Rivers | 64 | .15 | 64 | 0 |
| Mackay (WA) | 0 | 0 | 0 | 0 |
| Moore-Hill Rivers | 180 | .42 | 176 | 0 |
| Murchison River | 190 | .44 | 190 | 0 |
| Murray River (WA) | 897 | 2.08 | 593 | 0 |
| Ninghan | no data | 0 | 0 | |
| Nullarbor (WA) | 0 | 0 | 0 | 0 |
| Onslow Coast | 253 | .59 | 100 | 0 |
| Ord River (WA) | 3,870 | 8.97 | 4,202 | 0 |
| Pentecost River | 3,200 | 7.42 | 3,200 | 0 |
| Port Hedland Coast | 1,299 | 3.01 | 705 | 0 |
| Preston River | 145 | .34 | 141 | 0 |
| Prince Regent River | 3,360 | 7.79 | 3,360 | 0 |
| Salt Lake | no data | 0 | 0 | |
| Sandy Desert | 0 | 0 | 0 | 0 |
| Shannon River | 708 | 1.64 | 703 | 0 |
| Swan Coast | 683 | 1.58 | 569 | 279 |
| Warburton (WA) | 0 | 0 | 0 | 0 |
| Warren River | 411 | .95 | 380 | 0 |
| Wooramel River | 41 | .1 | 41 | 0 |
| Yarra Yarra Lakes | no data | 0 | 0 |
How saline are Western Australia's surface water resources?
Table: Surface water resource by salinity class for divertible yield (GL)
| Surface Water Managemnet Area | <500 mg/l (GL/yr) | 500 - 1500 mg/l (GL/yr) | 1500 - 5000 mg/l (GL/yr) | 5000 -14000 mg/l (GL/yr) | >14000 mg/l (GL/yr) | Total volume (GL/yr) |
|---|---|---|---|---|---|---|
| Western Australia | 11,174 | 733 | 471 | 180 | 0 | 14,949 |
| Albany Coast | 6 | 36 | 25 | 7 | 0 | 73 |
| Ashburton River | 40 | 0 | 0 | 0 | 0 | 40 |
| Avon River | 1 | 8 | 0 | 3 | 0 | 11 |
| Blackwood River | 198 | 330 | 12 | 29 | 0 | 568 |
| Busselton Coast | 272 | 0 | 4 | 0 | 0 | 275 |
| Cape Leveque Coast | 1 | 0 | 0 | 0 | 0 | 1 |
| Collie River | 72 | 0 | 111 | 0 | 0 | 182 |
| De Grey River | 226 | 0 | 0 | 0 | 0 | 226 |
| Denmark River | 36 | 20 | 22 | 0 | 0 | 78 |
| Donnelly River | 204 | 0 | 0 | 0 | 0 | 204 |
| Drysdale River | 1,390 | 0 | 0 | 0 | 0 | 1,390 |
| Esperance Coast | 1 | 5 | 0 | 0 | 0 | 5 |
| Fitzroy River (WA) | 2,511 | 0 | 0 | 0 | 0 | 2,511 |
| Fortescue River | 64 | 0 | 0 | 0 | 0 | 64 |
| Frankland River | 0 | 130 | 6 | 0 | 0 | 136 |
| Gascoyne River | 246 | 0 | 0 | 0 | 0 | 246 |
| Greenough River | 0 | 37 | 0 | 6 | 0 | 42 |
| Harvey River | 162 | 0 | 0 | 0 | 0 | 162 |
| Isdell River | 1,180 | 0 | 0 | 0 | 0 | 1,180 |
| Keep River (WA) | no data | no data | no data | no data | no data | 1 |
| Kent River | 29 | 52 | 0 | 0 | 0 | 80 |
| King Edward River | 770 | 0 | 0 | 0 | 0 | 770 |
| Lennard River | 502 | 0 | 0 | 0 | 0 | 502 |
| Lyndon-Minilya Rivers | 5 | 0 | 0 | 0 | 0 | 5 |
| Mackay (WA) | no data | no data | no data | no data | no data | 0 |
| Moore-Hill Rivers | 10 | 10 | 0 | 36 | 0 | 55 |
| Murchison River | 0 | 52 | 15 | 0 | 0 | 66 |
| Murray River (WA) | 139 | 10 | 1 | 0 | 0 | 149 |
| Ninghan | 1 | 0 | 0 | 0 | 0 | 1 |
| Nullarbor (WA) | no data | no data | no data | no data | no data | 0 |
| Onslow Coast | 15 | 0 | 0 | 0 | 0 | 15 |
| Ord River (WA) | no data | no data | no data | no data | no data | 2,391 |
| Pentecost River | 1,440 | 0 | 0 | 0 | 0 | 1,440 |
| Port Hedland Coast | 38 | 0 | 0 | 0 | 0 | 38 |
| Preston River | 66 | 0 | 0 | 0 | 0 | 66 |
| Prince Regent River | 1,087 | 0 | 0 | 0 | 0 | 1,087 |
| Salt Lake | 2 | 0 | 0 | 0 | 0 | 2 |
| Sandy Desert | 0 | 0 | 0 | 0 | 0 | 0 |
| Shannon River | 277 | 0 | 0 | 0 | 0 | 277 |
| Swan Coast | 113 | 50 | 18 | 100 | 0 | 280 |
| Warburton (WA) | no data | no data | no data | no data | no data | 0 |
| Warren River | 79 | 0 | 262 | 0 | 0 | 340 |
| Wooramel River | 0 | 0 | 0 | 0 | 0 | 0 |
| Yarra Yarra Lakes | 2 | 0 | 0 | 0 | 0 | 2 |
How much of Western Australia's surface water resource has been developed?
The total volume of surface water used within the State is estimated at 658 GL/yr, compared to 465 GL/yr in Review 85. Of the current annual use, 206 GL is used in urban areas and industry (including mining), 22 GL is used for rural purposes, and 430 GL is used in irrigation.
In the South West Division the total surface water use is indicated as being slightly lower than in Review 85. The explanation of this apparent decline comes largely from a decline in usage from public irrigation systems and partly from the effects of the sustained drought on the use of surface water in the Perth water supply system. The observed decline in public irrigation usage in the Busselton-Harvey region is particularly significant in regional terms and highlights the opportunities for future transfers through water markets. These opportunities will be facilitated by the transfer capacity of the Harvey development scheme currently in an implementation phase within the region.
In recent years, there has been a heavily increased demand on the Water and Rivers Commission in resolving allocation issues amongst self-supplied users in Busselton, Warren-Blackwood and Perth-Gingin (Moore) regions. This growth is not evident in comparisons between current use and Review 85 data as it is believed this difference is due to Review 85 data anticipating this future use by recording allocation in its compilation. These particular uses create demands on water resource regulators that are disproportionately high in relation to the scale of the resources in question.
In the Timor Sea Division, the dominant growth in use is associated with significant steps in development of the Ord Irrigation Area. At a much smaller scale, the demise of the Camballin Irrigation Scheme on the Fitzroy River is also reflected.
The Indian Ocean Division usage is dominated by the commissioning of the Opthalmia Dam and Harding Dam conjunctive use schemes for Mt Newman and the West Pilbara Water supply respectively.
How committed are Western Australia's surface water resources?
Under the national classification 4-class development status classification Western Australia has no surface water systems that are over developed and none that are highly or fully developed.
| Basin/SWMA | Volume diverted (GL/yr) | Sustainable (GL/yr) | Diversion Development class |
|---|---|---|---|
| Albany Coast | 4 | 34 | LOW DEVELOPMENT |
| Ashburton River | 0 | 28 | LOW DEVELOPMENT |
| Avon River | 2 | 10 | LOW DEVELOPMENT |
| Blackwood River | 14 | 184 | LOW DEVELOPMENT |
| Busselton Coast | 7 | 135 | LOW DEVELOPMENT |
| Cape Leveque Coast | 1 | 1 | LOW DEVELOPMENT |
| Collie River | 60 | 170 | MEDIUM DEVELOPMENT |
| De Grey River | 0 | 124 | LOW DEVELOPMENT |
| Denmark River | 1 | 51 | LOW DEVELOPMENT |
| Donnelly River | 2 | 91 | LOW DEVELOPMENT |
| Drysdale River | 1 | 166 | LOW DEVELOPMENT |
| Esperance Coast | 1 | 5 | LOW DEVELOPMENT |
| Fitzroy River (WA) | 1 | 737 | LOW DEVELOPMENT |
| Fortescue River | 7 | 10 | MEDIUM DEVELOPMENT |
| Frankland River | 2 | 6 | LOW DEVELOPMENT |
| Gascoyne River | 0 | 196 | LOW DEVELOPMENT |
| Greenough River | 2 | 38 | LOW DEVELOPMENT |
| Harvey River | 67 | 138 | MEDIUM DEVELOPMENT |
| Isdell River | 1 | 161 | LOW DEVELOPMENT |
| Keep River (WA) | 1 | 1 | LOW DEVELOPMENT |
| Kent River | 1 | 61 | LOW DEVELOPMENT |
| King Edward River | 1 | 177 | LOW DEVELOPMENT |
| Lennard River | 1 | 282 | LOW DEVELOPMENT |
| Lyndon-Minilya Rivers | 0 | 4 | LOW DEVELOPMENT |
| Mackay (WA) | 0 | 0 | LOW DEVELOPMENT |
| Moore-Hill Rivers | 4 | 21 | LOW DEVELOPMENT |
| Murchison River | 1 | 1 | LOW DEVELOPMENT |
| Murray River (WA) | 83 | 143 | MEDIUM DEVELOPMENT |
| Ninghan | 1 | 1 | LOW DEVELOPMENT |
| Nullarbor (WA) | 0 | 0 | LOW DEVELOPMENT |
| Onslow Coast | 0 | 12 | LOW DEVELOPMENT |
| Ord River (WA) | 271 | 1,295 | LOW DEVELOPMENT |
| Pentecost River | 1 | 196 | LOW DEVELOPMENT |
| Port Hedland Coast | 5 | 30 | LOW DEVELOPMENT |
| Preston River | 4 | 51 | LOW DEVELOPMENT |
| Prince Regent River | 1 | 145 | LOW DEVELOPMENT |
| Salt Lake | 1 | 2 | LOW DEVELOPMENT |
| Sandy Desert | 0 | 0 | LOW DEVELOPMENT |
| Shannon River | 5 | 64 | LOW DEVELOPMENT |
| Swan Coast | 116 | 242 | MEDIUM DEVELOPMENT |
| Warburton (WA) | 0 | 0 | LOW DEVELOPMENT |
| Warren River | 9 | 208 | LOW DEVELOPMENT |
| Wooramel River | 0 | 0 | LOW DEVELOPMENT |
| Yarra Yarra Lakes | 1 | 2 | LOW DEVELOPMENT |
The volume diverted is the total volume of the SWMA's surface water resources diverted for use both within the management area and for export to other management areas.
A four-class classification system was developed to provide a simple method to communicate the status of the use and allocation of Australia's water resources in relation to sustainable water management.
It is important to recognise that adequately quantifying a sustainable flow regime or sustainable yield and consequent operating rules is a complex matter. State, Territory and scientific agencies continue to develop and apply methods and measures for determining sustainable flow regimes and sustainable yields.
This categorisation provides a general guide only. Please refer to the State and Territory Overview and Technical reports for detail on the analysis methods used.
| Category | Development status | |
|---|---|---|
| 1 | <30% | Low development |
| 2 | 30 - 70% | Moderate development |
| 3 | 70 - 100% | Highly developed |
| 4 | 100% | Overdeveloped |
* Water use as a percentage of sustainable flow regime (surface water) and sustainable yield (groundwater)
How much groundwater does Western Australia have?
Hydrogeology
Groundwater recharge from rainfall may vary depending on rainfall conditions such as seasonal and annual variations in total rainfall and the intensity, duration and frequency of rainfall events. It is also affected by topography and drainage, soil cover, rock-types, land-use and other factors. In some areas groundwater recharge is increasing or decreasing as a result of changed land use such as clearing, urbanisation, or drainage.
In practice groundwater recharge has usually been estimated indirectly during regional groundwater investigations. The groundwater recharge has been estimated by dividing estimates of groundwater throughflow by the contributing area (average recharge = throughflow/recharge area), or from the ratio of chloride in rainfall to chloride in groundwater in recharge areas (average recharge = chloride in rainfall/chloride in groundwater x mean annual rainfall). These approaches provide results that are averaged over large areas and are generally considered to provide the most reliable recharge estimates for regional studies.
For the purpose of the Audit recharge factors for the Perth Basin were derived from existing management plans. For the remainder of Western Australia, they were derived from specific groundwater investigations, regional assessments, or were systematically estimated by reference to other areas and consideration of rainfall, topography and aquifer type.
Renewable Resource
The renewable, or total groundwater resource, was determined from the area of land surface or aquifer multiplied by the mean annual rainfall and by the applicable recharge factor for each defined area. Across the State, the renewable resource was estimated to be in the order of 7360 GL/yr.
Sustainable Yield and Environmental Allocation
Sustainable yields were based, in the first instance, on results derived from Groundwater Area Allocation Plans, (water) Management Plans, or on the outcomes of long term monitoring of water levels within an aquifer and associated abstraction volumes.
For most other Groundwater Management Areas/Unincorporated Areas within the State where detailed studies or long term monitoring data are not available, the sustainable yield for each was determined by deducting from the renewable groundwater resource estimate an allowance for wetlands and for seawater intrusion, where appropriate. ie:
Sustainable yield = renewable resources - wetlands allowance - seawater intrusion allowance.
The resulting sustainable yield estimates for the sedimentary and fractured rock divisions, together with a State total of 6304 GL/yr. While the fractured rock provinces appear to contain very significant volumes of groundwater resources, a significant proportion of these are distributed minor sources not amenable to high levels of utilisation.
How committed are Western Australia's groundwater resources?
Table: Allocation volumes (GL/yr in each development category)
Note: "GMU"=Groundwater Management Unit "UA"=Unallocated Area
| Province | Over | High | Med | Low | Total (GL/yr) | |
|---|---|---|---|---|---|---|
| Albany-Fraser 1 | GMU | no data | no data | no data | 1 | 1 |
| UA | no data | no data | no data | no data | no data | |
| Albany-Fraser 2 | GMU | no data | no data | no data | 0 | 0 |
| UA | no data | no data | no data | no data | no data | |
| Amadeus | GMU | 14 | no data | no data | 0 | 14 |
| UA | no data | no data | no data | 2 | 2 | |
| Arunta | GMU | 1 | 4 | no data | 0 | 5 |
| UA | no data | no data | no data | 3 | 3 | |
| Banemall | GMU | no data | no data | no data | 15 | 15 |
| UA | no data | no data | no data | no data | no data | |
| Bonaparte | GMU | no data | no data | no data | 2 | 2 |
| UA | no data | no data | no data | 1 | 1 | |
| Bremer 1 | GMU | no data | 4 | no data | 1 | 4 |
| UA | no data | no data | no data | no data | no data | |
| Bremer 2 | GMU | no data | 5 | 1 | 1 | 5 |
| UA | no data | no data | no data | no data | no data | |
| Calyie-Mcfadden | GMU | no data | no data | no data | 0 | 0 |
| UA | no data | no data | no data | no data | no data | |
| Canning | GMU | no data | no data | 10 | 8 | 17 |
| UA | no data | no data | no data | no data | no data | |
| Capricorn 1 | GMU | no data | no data | no data | 0 | 0 |
| UA | no data | no data | no data | no data | no data | |
| Capricorn 2 | GMU | no data | no data | no data | 3 | 3 |
| UA | no data | no data | no data | no data | no data | |
| Capricorn 3 | GMU | no data | no data | no data | 1 | 1 |
| UA | no data | no data | no data | no data | no data | |
| Capricorn 4 | GMU | no data | no data | no data | 1 | 1 |
| UA | no data | no data | no data | no data | no data | |
| Carnarvon | GMU | no data | 30 | 2 | 2 | 33 |
| UA | no data | no data | no data | no data | no data | |
| Collie | GMU | 24 | no data | no data | no data | 24 |
| UA | no data | no data | no data | no data | no data | |
| Eucla | GMU | no data | no data | no data | 0 | 0 |
| UA | no data | no data | no data | no data | 0 | |
| Halls Creek | GMU | no data | no data | no data | 7 | 7 |
| UA | no data | no data | no data | no data | 0 | |
| Hamersley | GMU | no data | 47 | no data | 33 | 79 |
| UA | no data | no data | no data | no data | no data | |
| Kimberley | GMU | no data | no data | no data | 0 | 0 |
| UA | no data | no data | no data | no data | no data | |
| Leeuwin | GMU | no data | no data | 2 | 1 | 3 |
| UA | no data | no data | no data | no data | no data | |
| Marymia | GMU | no data | 7 | no data | no data | 7 |
| UA | no data | no data | no data | no data | no data | |
| Musgrave | GMU | no data | no data | no data | 0 | 0 |
| UA | no data | no data | no data | 1 | 1 | |
| Northampton | GMU | no data | no data | no data | 3 | 3 |
| UA | no data | no data | no data | no data | no data | |
| Officer | GMU | no data | no data | no data | 0 | 0 |
| UA | no data | no data | no data | no data | 0 | |
| Ord-Victoria | GMU | no data | no data | no data | 0 | 0 |
| UA | no data | no data | no data | 6 | 6 | |
| Paterson | GMU | no data | no data | no data | 0 | 0 |
| UA | no data | no data | no data | no data | no data | |
| Perth | GMU | 4 | 414 | 204 | 123 | 745 |
| UA | no data | no data | no data | 1 | 1 | |
| Pilbara | GMU | no data | no data | 5 | 4 | 9 |
| UA | no data | no data | no data | no data | no data | |
| Sylvania | GMU | no data | no data | no data | 0 | 0 |
| UA | no data | no data | no data | no data | no data | |
| Tanami | GMU | no data | no data | no data | 0 | 0 |
| UA | no data | no data | no data | 1 | 1 | |
| Yilgarn-Gold Fields | GMU | no data | 97 | 25 | 15 | 136 |
| UA | no data | no data | no data | no data | no data | |
| Yilgarn-Murchison | GMU | no data | no data | 30 | 1 | 30 |
| UA | no data | no data | no data | no data | no data | |
| Yilgarn-Southwest | GMU | no data | 1 | 2 | 22 | 24 |
| UA | no data | no data | no data | no data | no data |
A four-class classification system was developed to provide a simple method to communicate the status of the use and allocation of Australia's water resources in relation to sustainable water management.
It is important to recognise that adequately quantifying a sustainable flow regime or sustainable yield and consequent operating rules is a complex matter. State, Territory and scientific agencies continue to develop and apply methods and measures for determining sustainable flow regimes and sustainable yields.
This categorisation provides a general guide only. Please refer to the State and Territory Overview and Technical reports for detail on the analysis methods used.
| Category | Development status | |
|---|---|---|
| 1 | <30% | Low development |
| 2 | 30 - 70% | Moderate development |
| 3 | 70 - 100% | Highly developed |
| 4 | 100% | Overdeveloped |
* Water use as a percentage of sustainable flow regime (surface water) and sustainable yield (groundwater)
How saline are Western Australia's groundwater resources?
Table: Groundwater resource by salinity class
| Province | <1500 mg/l (GL/yr) | 5000 mg/l (GL/yr) | 14000 mg/l (GL/yr) | >14000 mg/l (GL/yr) | Total volume (GL/yr) | |
|---|---|---|---|---|---|---|
| Western Australia | GMU | 513786.12 | 1162040.96 | 1112803.53 | 1499690.82 | 6286024.62 |
| UA | 37320 | 1852601 | ||||
| Albany-Fraser 1 | GMU | no data | no data | no data | no data | 4 |
| UA | no data | no data | no data | no data | no data | |
| Albany-Fraser 2 | GMU | no data | no data | no data | no data | 65 |
| UA | no data | no data | no data | no data | no data | |
| Amadeus | GMU | 13,848 | no data | 30 | no data | no data |
| UA | no data | no data | 79 | 20 | no data | |
| Arunta | GMU | no data | 5 | 11 | no data | no data |
| UA | no data | no data | 28 | 117 | no data | |
| Banemall | GMU | no data | no data | 66 | no data | no data |
| UA | no data | no data | no data | no data | no data | |
| Bonaparte | GMU | no data | no data | 123 | no data | no data |
| UA | 1,140 | no data | no data | 2 | no data | |
| Bremer 1 | GMU | no data | no data | 5 | 1 | 29 |
| UA | no data | no data | no data | no data | no data | |
| Bremer 2 | GMU | no data | 5 | 1 | no data | 30 |
| UA | no data | no data | no data | no data | no data | |
| Calyie-Mcfadden | GMU | no data | no data | no data | 95 | no data |
| UA | no data | no data | no data | no data | no data | |
| Canning | GMU | no data | 30 | 64 | 729 | no data |
| UA | no data | no data | no data | no data | no data | |
| Capricorn 1 | GMU | no data | no data | no data | 64 | no data |
| UA | no data | no data | no data | no data | no data | |
| Capricorn 2 | GMU | no data | no data | 19 | no data | no data |
| UA | no data | no data | no data | no data | no data | |
| Capricorn 3 | GMU | no data | no data | no data | 90 | no data |
| UA | no data | no data | no data | no data | no data | |
| Capricorn 4 | GMU | no data | no data | no data | 64 | no data |
| UA | no data | no data | no data | no data | no data | |
| Carnarvon | GMU | no data | no data | 5 | 20 | 213 |
| UA | no data | no data | no data | no data | no data | |
| Collie | GMU | 8,300 | no data | no data | no data | no data |
| UA | no data | no data | no data | no data | no data | |
| Eucla | GMU | no data | no data | no data | no data | no data |
| UA | no data | no data | no data | 5 | no data | |
| Halls Creek | GMU | no data | 218 | no data | no data | no data |
| UA | no data | 1 | no data | no data | no data | |
| Hamersley | GMU | no data | no data | 191 | 124 | no data |
| UA | no data | no data | no data | no data | no data | |
| Kimberley | GMU | no data | no data | no data | no data | 84 |
| UA | no data | no data | no data | no data | no data | |
| Leeuwin | GMU | 4,922 | 5 | no data | no data | no data |
| UA | no data | no data | no data | no data | no data | |
| Marymia | GMU | no data | 7 | no data | no data | no data |
| UA | no data | no data | no data | no data | no data | |
| Musgrave | GMU | no data | no data | 1 | 39 | no data |
| UA | no data | no data | 25 | no data | no data | |
| Northampton | GMU | no data | no data | no data | 1 | 16 |
| UA | no data | no data | no data | no data | no data | |
| Officer | GMU | no data | no data | no data | no data | no data |
| UA | no data | no data | no data | 1 | no data | |
| Ord-Victoria | GMU | no data | 102 | 91 | no data | no data |
| UA | 351 | 19 | no data | no data | no data | |
| Paterson | GMU | no data | no data | no data | 20 | no data |
| UA | no data | no data | no data | no data | no data | |
| Perth | GMU | 500,416 | 797 | 383 | 138 | 53 |
| UA | no data | no data | 38 | no data | no data | |
| Pilbara | GMU | no data | no data | 101 | 58 | no data |
| UA | no data | no data | no data | no data | no data | |
| Sylvania | GMU | no data | no data | no data | 6 | no data |
| UA | no data | no data | no data | no data | no data | |
| Tanami | GMU | no data | no data | 25 | no data | 95 |
| UA | no data | 19 | 15 | no data | no data | |
| Yilgarn-Gold Fields | GMU | no data | no data | no data | no data | 69 |
| UA | no data | no data | no data | no data | no data | |
| Yilgarn-Murchison | GMU | no data | no data | no data | 57 | 51 |
| UA | no data | no data | no data | no data | no data | |
| Yilgarn-Southwest | GMU | 148 | 2 | 5 | 3 | 65 |
| UA | no data | no data | no data | no data | no data |
How much water does Western Australia trade?
The Total reported Volume Traded in Western Australia is 0 GL; in 0 transactions.
The State and Territory water management agencies continue to consider water use efficiency and optimisation strategies within existing infrastructure (e.g. water supply efficiency, precision irrigation and scheduling, water recycling, trading and pricing) as part of water resource development planning.
Recognising that water is a finite resource, the States and Territories have developed water allocation systems where security and reliability are assigned to entitlement, trading is provided so water can be moved to high value uses and the choices of individuals are maximised.
Part of the decision-making framework to enable and facilitate water trading, changes in water allocation and definition of rights to water is the need for water use monitoring. Water use monitoring will assist decision-making and provide an opportunity over time to evaluate the effectiveness of allocation policies.
Environmental water requirements
Estimation of sustainable yields was undertaken as a two-stage process.
The first stage, or first cut, involved accumulating sub area data to the SWMA scale, for the likely development scenario. This development scenario included applying all constraints explicit or strongly implicit in established regional allocation plans, policy or regulations, in the selection of preferred sites.
Similarly for divertible yield calculations, individual sub area yields were adjusted to reflect the interaction of sites in the adopted development scenario.
First cut sustainable yields were then estimated based on applying management objective factors.
Second Cut Sustainable Yield Estimation
The second cut involved refinement of selected sites for the likely development scenario established in the first cut, and further adjustment of management objective factors (environmental water provisions) for individual sites.
This second cut refinement aimed to provide allowances for regional reservations yet to be established. While the second cut involved subjectivity, the refinements made were based on accumulated regional planning experience, and are believed to reflect realistic outcomes at SWMA levels.
The calculated second cut sustainable yields at SWMA level represent the surface water sustainable yields reported by Western Australia for the purposes of the Audit.
Interpretation of Method
Sustainable yield estimates for the Audit at SWMA level should be interpreted as indicative of the broad outcomes of a planning process which has approached sustainability through application of precautionary principles for determination of environmental reservations and environmental flow provisions.
Although calculated at the sub area level, sustainable yield estimates at the sub area level do not have sufficient specific information to be regarded as prescriptive, except where environmental water provisions have been formally established. It is considered invalid to interpret these sub area assessments as definitive in a planning sense.
Further information
- Western Australia Water Resources Assessment 2000 Report
- Western Australia Water Resources Assessment 2000 Technical Report
- report from the study of Streamflow data and modelled streamflow
- Link to data available for download on the:
- extension of unimpaired monthly streamflow data and regionalisation of parameter values to estimate streamflow in ungauged catchments (NLWRA 2000)
- Surface Water Management Areas
- Groundwater management units and provinces - ARC/INFO export
- Link to the Map Maker to make a map using this information.
Key
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