Australia's Natural Resources
1997-2002 and beyond
National Land and Water Resources Audit, 2002
Key Findings—Water
Only 12% of Australia's rainfall runs off to collect in its rivers.
- Of the water collected in Australian rivers, nearly half runs off into the Timor Sea and Gulf of Carpentaria from the adjacent drainage divisions.
There is a net utilisation of about 20% of the potentially divertible water resources in Australia.
- The mean figure for water use (20%) masks the great variation in the distribution of use. Some areas of the country such as the northern coastline have little use of divertible water resources. Other areas have significant use, notably the Murray-Darling Basin where provision of adequate water for the environment has become an important policy issue.
Figure 35. Percent of total Australian run-off from each drainage division. Bold percentages after each division caption represent proportion from division diverted for use.
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Australia's mean annual water use in 1996/97 was about 19 000 GL of surface water and 5000 GL of groundwater.
- The area irrigated since the 1980s increased by approximately a 26%. This increase underlies much of Australia's increased agricultural production.
Table 3. Total area ('000 ha) of commodity groups in Australia that were irrigated in 1983/84 and 1996/97.
Commodity group 1983/84 1996/97 Increase
('000 ha)Increase
(%)Pastures 871 935 64 7.3 Cereals 315 337 22 6.9 Vegetables 76 87 11 14.5 Fruit 97 151 54 55.7 Other crops* 260 544 284 109.2 Total 1625 2056 431 26.5
* 'Other crops' are made up mainly of cotton, sugar cane and soybean
Figure 36. Change in mean annual surface water use (GL) between 1983/84 and 1996/97 largely attributable to increase in irrigation.
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Groundwater use markedly increased in the period 1983/84 to 1996/97.
- The increasing use of groundwater in most States and Territories (88% overall since 19983/84), indicates the need for increasing knowledge and management of our groundwater resources.
Figure 37. Change in mean annual groundwater use (GL) between 1983/84 and 1996/97.
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Groundwater management areas are now defined.
- For the first time groundwater management areas have been defined for Australia and information collated on each of these 535 areas. There is considerable variation in the developed yield taken from the various provinces.
Figure 38. Sustainable yield of groundwater provinces.
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Ensuring sustainable use of surface water is a priority.
- Many of Australia's surface water resources have limited opportunities for further development. Eighty-four (26%) of Australia's 325 surface water management areas, drawn from the 246 recognised river basins, are either close to or overused compared with their sustainable flow regimes.
Figure 39. Levels of surface water commitment for Australia's surface water management areas.
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Many groundwater resources require increased management to achieve sustainability.
- The water from 168 of Australia's 538 groundwater management units is either totally allocated or is already over-allocated. Not all allocated water entitlements are used, but 161 (30%) of Australia's 538 groundwater management units are close to or overused compared with their sustainable yield. There is scope for further development and finetuning of groundwater management policies to more effectively underpin sustainable resource management. Mapped at province scale (Figure 40), the abstraction development category demonstrates the key areas of groundwater use and the relative levels of management needs.
Figure 40. Groundwater development status-in some provinces, abstraction exceeds recruitment to the resource, notably in the Great Artesian basin.
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Irrigation is a major contributor to Australian agriculture.
- Half of the profit in 1996/97 from Australian agriculture when measured as profit at full equity was generated from irrigated production systems. These occupy less than 0.5% of Australia's land area. Continued emphasis on improved irrigation practices will ensure increasing productivity and better land and water management.
Figure 41. Irrigation areas of Australia.
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There is a wide range in economic return from irrigation.
- Different irrigation enterprises and the intensity of use of water in those enterprises leads to a wide range in the economic benefits achieved from irrigation. There is scope for further rationalisation of water use and increases in returns as water use moves to higher value products.
Table 4. Annual returns to water and intensity of water use (PFE 1996/97)*.
Land use Water returns
$/MlTotal water use
GlPer cent of total water use
%Water use
ML/haVegetables 1295 392 2.6 3 Fruit 1276 665 4.4 7 Tobacco 985 13 0.1 4 Grapes 600 781 5.2 8 Tree nuts 507 140 0.9 6 Cotton 452 2 314 15.5 7 Coarse grains 116 518 3.5 3 Dairy 94 5 902 39.5 7 Peanuts 90 25 0.2 3 Hay 54 20 0.1 4 Rice 31 1 696 11.3 11 Legumes 24 33 0.2 3 Sheep 23 13 0.1 4 Sugar cane 21 1 195 8.0 7 Beef 14 1 080 7.2 4 Oilseeds 10 85 0.6 3 Cereals -9 87 0.6 3 All irrigated land uses 193 14 959 100.0 7
* Derived from estimates of mean water use per land use type in each region
Increasing the area under irrigation provides a development opportunity for northern Australia
- 241 surface water units and 265 groundwater units have minimal or no development. Many of these are in arid environments where development potential is minimal to nil. The greatest unallocated water resources are in northern Australia. Northern Territory government resource planners estimate that the area of irrigated agriculture could sustainably expand 30 to 40 times. Based on an annual water consumption of 10 Ml/ha/year the area for potential irrigation in the Top End was projected to be 27 500 ha (groundwater) and 85 600 ha (surface water). This assessment required no on-stream dams to be constructed, ensured adequate water allocations for environmental flows (80% of streamflow or recharge) and required land clearances in river basins of <4% (Table 5). Knowledge of tropical systems, water use technology, irrigated production systems and potential commodity markets from these tropical environments is still developing. Much of the rest of Australia, particularly the southern settled areas and the arid zone, has very limited potential for further development.
Table 5. Projected area with potential for irrigation development in the Top End region of northern Australia.
River basin Basin area
(km2)Potential irrigable
area*
(ha)Total basin clearing
(irrigation, fallow, dams)(ha) (% of basin) Ord River 55 380 Groundwater nil nil nil Surface water 56 000 181 000 3.3 Victoria River 77 230 Groundwater nil nil nil Surface water 10 400 34 300 0.5 Moyle River 7 020 Groundwater 5 000 15 000 2.2 Surface water nil nil nil Adelaide River 7 430 Groundwater nil nil nil Surface water 4 000 13 200 1.8 Mary River 8 060 Groundwater 2 500 7 500 1.0 Surface water nil nil nil Blyth River 9 080 Groundwater 2 500 7 500 0.9 Surface water nil nil nil Roper River 79 130 Groundwater 3 000 9 000 0.1 Surface water 14 400 47 500 0.6 Daly River 52 940 Groundwater 14 500 43 500 0.8 Surface water 40 000 132 000 2.5 McArthur River 19 200 Groundwater nil nil nil Surface water 16 800 55 400 2.9
Data source: Northern Territory Department of Lands, Planning and Environment
* Estimated at 10 Ml/ha/yr
Multi-objective assessment methods are becoming available to evaluate the potential for irrigation developments.
- The Audit sponsored the formulation of Large scale resource developments—an integrated assessment process (NLWRA 1999) to define methods that improve evaluation of water resource development proposals. This method has been adapted and modified to meet State and Territory needs and used to assess several projects in Queensland and Tasmania.
Water distribution efficiency can be improved and provides a development opportunity.
- There are great variations in the delivery systems used to supply irrigation water. On average, only 77% of water reaches users' properties. Supply efficiency can be as low as 45% in some irrigation areas. There is technology to address these issues and it provides a major opportunity for improving water resource management in southern Australia.
Figure 42. Water distribution efficiency for irrigation supply systems in Australia.
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Efficiency of water use is quite variable.
- Both market and technological options are available for maximising the efficiency of water use, and some growers have readily adopted best practice options. A recent example is the introduction of partial root zone drying in the irrigated horticultural and viticultural industries. There remains a great variation in the economic and physical efficiency with which water is applied within individual agricultural commodity production systems, and a further variability in production outputs achieved. Industry codes of practice such as that developed for the dairy industry are addressing these issues and will provide a sound basis for continuous improvement.
Table 6. Irrigation statistics for dairy industry regions.
Region % of farms
irrigating
(%)Average
area irrigated
(ha)% of irrigating
farms using
flood irrigation
(%)% of irrigating
farms using
spray irrigation
(%)Average irrigation
water application
rate
(ML/ha)Average irrigation
water usage
rate
(ML/cow)West Victoria dairy 25 34 16 89 4.5 0.9 Gippsland dairy 29 60 58 53 4.1 1.3 Murray dairy 92 98 96 10 6.0 2.6 Dairy Industry Development Company (NSW) 57 49 5 98 4.5 1.4 Subtropical dairy 62 29 2 100 4.5 0.9 Dairy Tasmania 62 45 2 99 2.7 0.5 Dairy Western Australia 42 41 92 13 9.5 2.1 Dairy South Australia 71 46 27 86 5.4 1.3 Australian average 57 64 49 56 5.3 1.9
Data Source:
Australian Agriculture Assessment 2001
Data used are assumed to be correct as received from the data suppliers
©Commonwealth of Australia 2001
Water quality assessment has defined the priority catchments for the National Action Plan for Salinity and Water Quality.
- Approximately one-quarter of Australia's 246 basins can be adequately assessed for the key variables of turbidity, nutrients and salinity.
- Water quality was found to exceed acceptable standards for nutrients in 43 basins.
- Water was excessively turbid in parts of 41 basins.
- Water quality exceeded salinity standards in 24 basins.
Figure 43. Water quality issues—major quality issues affecting more than 33% of a drainage basin.
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Soil erosion and in-stream turbidity are clearly major issues for eastern Australia.
- Turbidity deriving from soil loss has a particularly strong impact on water quality in much of eastern Australia. The Audit's assessment of water-borne erosion provides the key for targeting works and activities to address this issue.
Figure 44. Soil loss, leading to turbidity, remains a major issue in much of eastern Australia.
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Turbidity is equally important as salinity in downstream costs.
- Soil management to minimise erosion and hence turbidity has immediate benefits and is likely to provide a more rapid return on investment than activities to minimise dryland salinity.
Figure 45. Present values of downstream costs associated with increases in water quality parameters over the period 2000 to 2020. Estimates of costs are given for making incremental improvements of 5% (left) and 10% (right) in water quality.
