Australia State of the Environment Report 2001 (Theme Report)
Prepared by: Jonas Ball, Sinclair Knight Merz Pty Limited, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06750 7
One of the most significant pressures on inland aquatic ecosystems is water extraction from surface water and groundwater resources for human uses. With Australia's growing population and increases in area of irrigated land, the volume of water extracted for human uses has increased considerably over the past 15 years. The rate of extraction from some surface water and groundwater resources is close to or exceeds the sustainable yield of the water resource, and their associated aquatic ecosystems are suffering from the effects of over-extraction and over-development.
The following discussion has been divided into three subsections. Firstly, changes and trends in Australia's total water use and the types of uses (i.e. irrigation, drinking-water supply) since the last water use review are assessed. In the second and third subsections, the effect of water extraction on surface water and groundwater resources, respectively, is assessed including:
- identifying river systems and groundwater resources where current water extraction is not sustainable
- identifying river systems and groundwater resources where increases in water extraction may be sustainable
- reviewing current management responses to water use including environmental flow allocations and progress on National Water Reforms.
The impact of water extraction on inland aquatic ecosystems is discussed in Aquatic ecosystems.
The water resources section in this SoE Report differs from Australia: State of the Environment 1996 (State of the Environment Advisory Council 1996) in a number of ways. The National Land and Water Resources Audit (NLWRA) has provided updated information on water use and water availability and includes data on sustainable yields (NLWRA 2001a). Sustainable yields include environmental water allocation for the maintenance of the health of aquatic ecosystems and are considerably lower than the divertible yields. There have also been substantial changes to the management and allocation of water resources primarily due to national water reform processes.
This section reports on the following environmental indicators, which are defined in Fairweather and Napier (1998):
|IW 4.1||Resources versus demand|
|IW 4.2 | a | b |||Surface water distribution|
|IW 4.4||Environmental flow objectives|
|IW 4.7||Water use|
|IW 4.8||Irrigation extent|
|IW 4.9||Water pricing|
|IW 4.10||Irrigation efficiency|
|IW 4.11||River structures|
People use water in a non-consumptive manner for fishing, aquaculture, hydroelectric power generation and recreation. However, it is the consumptive use of water for irrigation, drinking water and industry that has the greatest impact. The following discussion relates to the consumptive use of water.
The last comprehensive review of Australia's water resources and water use was in 1985 (AWRC 1987) and formed the basis of the water resource information in Australia: State of the Environment 1996 (State of the Environment Advisory Council 1996). In 1985, water use in Australia was 14 600 GL, with 70% used for irrigation, 21% used for urban and industrial purposes and 9% used for rural (stock and domes tic) purposes (Table 1). Eighteen per cent of the total water used was extracted from groundwater resources (2600 GL/year), while 82% was extracted from surface waters (12 000 GL/year).
|Water use category||1985 ReviewA||1996/97 ReviewB||Percentage change|
|Irrigation||10 200||17 935||76|
|Urban / industrial||3 060||4 754||55|
|Rural||1 340||1 369||2|
|TOTAL||14 600||24 058||65|
A AWRC 1987.
B NLWRA 2001.
Total water use in Australia for 1996/97 was 24 058 GL (NLWRA 2001a), an increase of 65% from 1985 (AWRC 1987). It must be noted that some of the increase was due to improved accounting of water use. Seventy-nine per cent of water used was from surface waters (19 109 GL), while 21% was from groundwater resources (4962 GL) (NLWRA 2001a).
Irrigation is by far the greatest use of water in Australia, using 75% of water extracted. Over the period 1985 to 1996/97, irrigation water use grew at a faster rate than urban/industrial water use. Rural water use, which consists primarily of stock and domestic water use, has increased slightly, but now only is 6% of total water use in Australia.
The extent and trends in irrigation are described in detail in the Land Theme Report and are summarised below. Over the last 20 years the area of irrigated land has almost doubled in New South Wales and Queensland and has remained relatively constant in most other states and territories. In 1997, 1.472 million hectares of land were irrigated in the Murray-Darling Basin, which is 71% of the total area irrigated in Australia. Water use for a range of irrigated crops is shown in Figure 1.
Figure 1: Total annual irrigation water use 1996/97 by crop type.
Source: Australian Bureau of Statistics 2000.
The current trend in irrigated agriculture is towards large-scale enterprises growing high-value horticulture, viticulture, cotton, rice and/or vegetables. In the Murray-Darling Basin, the area of irrigated land will only increase with improvements in irrigation efficiency or increased development of groundwater resources, as surface water use is capped at the 1993/94 levels of development. Increases in irrigated land and water use are likely to occur in the relatively undeveloped northern drainage regions.
Although urban and industrial water users account for only 20% of total water use, the localised effect of this demand on the river systems can be significant. Most drinking water supplies are from the catchments surrounding urban centres. At least 50% and up to 90% of divertible water resources have already been developed in the catchments containing the major state capitals (NLWRA 2001b). A higher quality of raw water is also required for urban water supply to limit the costs of treating it to drinking water quality and to reduce the risk of contamination and disease. To ensure high quality water supplies, the protection and maintenance of a healthy catchment and the minimisation of water pollution is essential.
- Total annual water use in Australia between 1985 and 1996/97 has increased by 65% to 24 058 GL/year. Surface water extraction accounts for 79% of total water use while groundwater accounts for 21% of total use.
- Over the past 20 years, the area of irrigated land has almost doubled in New South Wales and Queensland, and there has been a 75% increase in the annual volume of water used for irrigation between 1985 and 1996/97.
- Drinking and industrial water use has increased by 55% between 1985 and 1996/97.