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In this section you will find detailed information, including national overviews and state and regional level assessments, from the 2000-2002 National Land and Water Resources Audit theme assessments.
Water - Water Availability
Scarce, variable, harnessed
Characterisation of water resources
A key part of Australian Water Resources Assessment 2000 was the collation of data on the characteristics of Australia's surface and groundwater resources.
Australia has excellent information on its surface water availability as a result of a long period of strategic investment, fostered and encouraged through previous Commonwealth initiatives such as the Australian Water Resources Council. These data were collated to make them accessible as input to analysis of natural resource management issues such as river, wetland or estuary management, catchment hydrology or the catchment scale assessment of land use change options. These land use change options and an assessment of their impacts on our natural resources in total will be needed for salinity management as Australia moves towards implementing targets under the National Action Plan.
To facilitate various applications, data were collated under a rigorous database structure that is now part of the Audit's Data Library. Access to the data library will be managed by the Bureau of Rural Sciences and in accordance with any licence arrangements that a particular State may wish to impose on specific data.
These data were collated to provide summary information derived from the databases as input to activities such as regional planning and to improve community understanding of the nature of Australia's water resources. Information on Australia's surface and groundwater resources is available through the Audit's Australian Natural Resources Atlas in a hierarchy from Australia-wide to drainage divisions to basins to individual stream gauging stations or bore monitoring sites. By providing readily available access to information on Australia's natural resources, the Atlas will be a key tool for regional groups as they develop and then monitor progress in their regional natural resources strategies.
Surface water characterisation
Attributes collated for quantitative resource characterisation for surface water management areas were:
Water availability
- Divertible yield: average annual volume (ML) that could be diverted using both existing and potential infrastructure and under an ultimate level of infrastructure development scenario-making no allowance for environmental water requirements.
- Developed yield: average annual volume (ML) that can be diverted for use by existing infrastructure. Developed yield represents the portion of the divertible yield that is potentially available for use.
- Developed use: average annual volume actually diverted for use.
Hydrogeological characteristics
- Mean annual flow: average annual volume of water streamflow passing a specified point on a stream
- Mean annual inflow: average annual volume of water flowing into a surface water management area
- Mean annual outflow: average annual volume of water flowing out of a surface water management area
- Mean annual run-off: streamflow generated as a result of direct precipitation on the area of interest
- Hydrograph: actual and natural (for mostly regulated systems) monthly hydrographs. Daily flow estimations of streamflow for a run of 100 years are also available for 350 sites based on a rainfall-run-off model that uses the Bureau of Meteorology 100-year rainfall record.
- Hydrometric statistics: annual* and monthly statistics for actual and natural flow regimes; mean flow; normalised flow; standard deviation; normalised standard deviation; minimum flow; maximum flow; coefficient of variation and auto correlation
* Annual statistics are based on years with a full 12 month record and consequently may introduce bias/error into the statistics.
Use and other features
- Major infrastructure: location and volumes of dams and weirs
- Major diversion: location and volume
- Water traded: volume and number of transactions of water traded within or between surface water management areas
- Water imported: volume of water imported into a surface water management area
Groundwater characterisation
Attributes collated for groundwater management units were:
Water availability
- Sustainable yield: average annual volume that can be abstracted for use taking account of environmental water provisions
- Abstraction: average annual volume extracted for use
- Major abstractions: location and volume
Note: The total storage volume of groundwater aquifers was not determined as it was not considered to be a particularly useful measure from a water management or use perspective.
Aquifer characteristics
- Depth: average depth to aquifer
- Thickness: saturation thickness
- Salinity: salt concentration as measured by electrical conductivity in microSeimens per centimetre (µS/cm)
- Hydrographs: monthly hydrographs
Continued updating of these datasets is essential so that the information is current and available to support decision making. Updating could be undertaken through review and, where necessary, improvement of data management arrangements in place within States and Territories. Summary reporting at regular intervals as part of ongoing water resource assessments is also essential and would provide a framework for strategic management of Australia's water resources.
Surface water availability
Australia is a dry continent. Rainfall is distributed unevenly-both geographically and seasonally.
Figure 5. Average annual rainfall based on 30-year climatology (1961-1990)
On average, only 12% of rainfall runs off to collect in rivers: in five of Australia's 12 drainage divisions, run-off is less than 2%; in the two drainage divisions of tropical monsoonal divisions of Timor Sea and Gulf of Carpentaria, run-off is greater than 20%. The remaining 88% of rainfall is accounted for by evaporation, water used by vegetation; and water held in storages including natural lakes, wetlands and groundwater aquifers.
Figure 6. Percent run-off from each drainage division.
Source: AATSE 1999
Table 3. Run-off, outflows and diversion from each drainage division.
| Drainage division | Mean annual run-off (GL) | Percent mean annual run-off (%) | Mean annual outflow (GL) | Volume diverted (GL) |
|---|---|---|---|---|
| North-East Coast | 73 411 | 19.0 | 69 580 | 3 182 |
| South-East Coast1 | 42 390 | 10.9 | 40 366 | 1 825 |
| Tasmania2 | 45 582 | 11.8 | 45 336 | 451 |
| Murray-Darling1 | 23 850 | 6.2 | 5 750 | 12 051 |
| South Australian Gulf 3 | 952 | 0.2 | 787 | 144 |
| South-West Coast | 6 785 | 1.8 | 5 925 | 373 |
| Indian Ocean | 4 609 | 1.2 | 3 481 | 12 |
| Timor Sea | 83 320 | 21.5 | 81 461 | 48 |
| Gulf of Carpentaria | 95 615 | 24.7 | 96 066 | 52 |
| Lake Eyre | 8 638 | 2.2 | n/a | 7 |
| Bulloo-Bancannia | 546 | 0.1 | - | <1 |
| Western Plateau | 1 486 | 0.4 | n/a | 1 |
| Total | 387 184 | 100 | 18 147 |
1 South-East Coast and Murray Darling Division. The volume diverted represents the sum of available data (New South Wales has not reported water use for unregulated surface water management areas)
2 Tasmanian Division. Volume diverted does not include the HYDRO scheme diversions.
2 South Australian Gulf Division. Mean annual outflow includes the flow from surface water management areas Willochra Creek and Lake Torrens, which do not flow to the sea but into the terminal lake - Lake Torrens.
Figure 7. Developed yield of surface water management areas (2000)
River flow is highly variable and driven largely by an irregular climate. Diversion of water into irrigation has significantly altered, and sometimes (e.g. mid-lower Murray-Darling Basin) led to the reversal of the annual river flow patterns (Figure 8).
Figure 8. Mean monthly river flow at Albury (An Audit of Water Use in the Murray-Darling Basin, June 1996).
Australia has 447 large dams with a combined capacity of 79 000 GL of water (equivalent to 158 times the volume of Sydney Harbour) developed mainly for urban, irrigation and hydroelectric power users. Australia's several million farm dams account for an estimated 9% of the total water stored.
Figure 9. Storage capacity (GL) in large dams to 1990 (IEA 1999).
* Does not include Googong Dam (125 GL) which is an Australian Capital Territory-owned dam located in New South Wales.
Groundwater availability
Australia has 25 780 GL of groundwater that can be extracted sustainably each year and is suitable for potable*, stock and domestic use, and irrigated agriculture. Ten percent (2489 GL) is used. Groundwater's importance as a proportion of total use varies (e.g. in Western Australia groundwater use is twice surface water use; in New South Wales and Victoria, use is predominately from surface water).
Australia has one of the world's larger aquifer systems: the Great Artesian Basin is an estimated 1.7 million km2 and stores 8 700 000 GL. Each year the Great Artesian Basin supplies 570 GL of water for a variety of uses-mainly grazing and mining.
Figure 10. Sustainable yield of groundwater provinces
Achievements
- Overall, the characteristics of Australia's surface waters are well defined in all States and Territories.
- Groundwater resources are well characterised in some States (e.g. Western Australia). The definition of groundwater management units for Australia is a major advance undertaken as part of this assessment and provides a framework for improved groundwater management.
Table of Contents for the Australian Water Resources Assessment 2000
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