Australia State of the Environment Report 2001 (Theme Report)
Lead Author: Professor Peter W. Newton, CSIRO Building, Construction and Engineering, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06747 7
Urban stocks and processes (continued)
Rainfall and river flow patterns have had a major influence on the development of settlement in Australia. Most major towns and cities are on the coast, in locations where rainfall and river flows are larger and more reliable (AATSE and IEAust 1999). Canberra and several established mining towns such as Kalgoorlie and Mt Isa are some of the exceptions.
Australia comprises a little over 5% of the world's land area, but its proportion of global river runoff is less than 1% (Smith 1998). Mean annual runoff from the continent of Australia is 12% of precipitation, compared to 38% in Europe and North America (Crabb 1997), due largely to high evaporative losses.
There is great geographic variability in rainfall and runoff, and as a consequence there is a great spatial variability in divertible water resources, as seen in Table 24. (A divertible resource is fresh water that can be economically and sustainably developed, not accounting for environmental requirements or availability of the infrastructure necessary.) It is worth noting that these are mean values and that the spatial distribution varies from year to year due to temporal variations. Rainfall and runoff is not only low and seasonal, but irregular compared with other continents such as Europe and North America (AATSE and IEAust 1999). The annual variation in runoff in Australia for all catchment sizes, as measured by the coefficient of variation, is 60% greater than the world average and 250% greater than Europe (Smith 1998). As a consequence of the variability of runoff, large volumes of water storage (on a per capita basis) have been established to provide security of supply. For example, Sydney has a water storage capacity of 932 000 litres per capita, while New York has 250 000 litres per capita and London has 182 000 litres per capita (Crabb 1997).
|Region||Divertible fresh water resources (GL)||Volume used (GL)||Proportion utilised (%)|
|Queensland coast||6 000||1 220||7 220||2 740||38|
|Queensland part of Lake Eyre Drainage Basin||160||170||330||80||24|
|Queensland: Carpentaria and Cape York||20 130||620||20 750||400||2|
|NSW coast||11 160||820||11 980||1 460||12|
|Victorian coast||3 830||380||4 210||1 030||24|
|Tasmania||10 860||180||11 040||560||5|
|NSW part of Murray-Darling Basin||5 140||710||5 850||6 750||115|
|Victorian part of Murray-Darling Basin||6 530||60||6 590||3 790||58|
|Queensland part of Murray-Darling Basin||720||230||950||370||39|
|SA part of Murray-Darling Basin||20||0||20||500||2 500|
|South-east coast of SA||80||1 090||1 170||490||42|
|Adelaide and hinterland||150||230||380||290||76|
|South Australia, Eyre Peninsula and northern SA||10||320||330||80||24|
|South-west of Western Australia||1 390||730||2 120||980||46|
|Goldfields and Esperance||10||50||60||30||50|
|Gascoyne and Pilbara||300||90||390||150||38|
|Kimberley||8 660||490||9 150||130||1|
|Northern Territory||17 320||2 420||19 740||120||1|
|Total||92 470||9 810||102 280||19 950||20|
Source: AATSE and IEAust (1999).
It has been estimated that 20% of Australia's divertible surface water resources were utilised in 1995-1996, although this rate varies considerably, from 1% in the Northern Territory and the Kimberley to 2500% in the South Australian part of the Murray-Darling Basin. (This extremely high utilisation rate in the South Australian part of Murray-Darling Basin is due to the limited divertible water resources generated within the region and its reliance on flows generated in the Basin upstream of the region.)
Tasmania and the region north of the Tropic of Capricorn account for more than half of the divertible water resources but only a very small proportion of the nation's population (Anderson 1995, Crabb 1997). Two-thirds of Australia's population lives in New South Wales, Victorian and Queensland coastal regions, which collectively have 23% of the divertible water resources. However, at a finer spatial scale within these zones, development rates can be much higher. For example, in the Brisbane water region 100% of divertible water resources are developed, in the Melbourne water regions 70% are developed, and in the Sydney Water Corporation region 57% (Crabb 1997).
In most large cities, the volume output of stormwater and wastewater significantly exceeds the input from the existing water supply. For example, in one year Sydney Water Corporation supplied 636 GL of water to Sydney and collected 548 GL of wastewater (WSAA 1999), while on average some 420 GL/year of stormwater runoff is discharged (Argent 1995). Therefore, the output of stormwater and wastewater (968 GL) exceeded the input from the water supply (636 GL) by about 50%. Urban water stocks in the 21st century need the potential resource of stormwater and wastewater to be added to conventional water stocks in order to provide an overall representation of the total water resource availability. For example, the average volume of stormwater discharged nationally is about 3000 GL per year (Anderson 1995), whereas 1829 GL of domestic water was used nationally in 1996-97 (ABS 2000f). Approaches such as least cost planning provide a method for evaluating the benefits and costs of stormwater and wastewater utilisation, alongside other options such as demand-side management and traditional supply augmentations to determine the best option for delivering water services in the future.
In the 1996-97 financial year, 8% of water use in Australia was by the domestic sector, 22% was used for industrial and commercial purposes, and the remainder used by the rural sector (Table 25). A key feature is that, while shares between sectors in recent years have been relatively stable, water use has been growing in volumetric terms across all sectors. On a global scale, the dominance of the agricultural sector is not an unusual feature, although Australia's use is higher than most industrial countries; for example, agricultural usage is 33% in Europe and 49% in North America (Smith 1998).
|Year||Domestic||IndustrialA||Commercial||Rural||Total water use|
|1977||1 780 (10%)||890 (5%)||534 (3%)||14 596 (82%)||17 800|
|1983-84||1 790 (12%)||790 (6%)||481 (3%)||11 540 (79%)||14 600|
|1993-94||1 704 (9%)||4 195 (22%)||498 (3%)||12 179 (66%)||18 575|
|1994-95||1 799 (9%)||4 114 (19%)||522 (2%)||14 706 (70%)||21 142|
|1995-96||1 691 (9%)||4 397 (22%)||463 (2%)||13 325 (67%)||19 875|
|1996-97||1 829 (8%)||5 174 (20%)||509 (2%)||15 522 (70%)||22 186|
AThe 1993-94 to 1996-97 industrial sector volumes include losses due to environmental flows, seepages and evapotranspiration, as well as water use by the water supply, sewerage and drainage services industry. The 1977 and 1983-84 industrial sector volumes do not include losses due to environmental flows, seepages, and evapotranspiration.
Source: AWRC (1981); DPIE (1987); ABS (2000f).
The Inland Waters Theme Report provides further details on water use and (through the National Land and Water Resources Audit) has isolated irrigation from other water uses. The differing methodologies in that report, compared with the ABS water accounts used here, has led to a different total water use figure of 24 060 GL for the 1996-97 year.
Figure 34 provides a snapshot of total annual water use across Australia's states and territories by sector of industry. Key points to note are the significant variations by state in volume of water use, linked to the underlying population and industry base. Levels of domestic, commercial and industrial use are relatively stable year to year (except in the Northern Territory), with greatest change occurring in rural water use, reflecting climatic variability.
Figure 34: Water use by sectors in states and territories, 1993-94 to 1996-97. [HS Indicator 2.3]
Source: ABS (2000f)
There can be a significant local variation in water use by a particular sector within a state or territory. For example, in Queensland's Curtis region, centred on Gladstone, industrial uses accounted for over 56% of the total demand in 1990 (Crabb 1997).