Human Settlements Theme Report

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)

Water (continued)

Changing pattern of urban water use

The amount of water consumed in a city depends on the activities occurring within its boundaries; each city has its own climatic context and economic base, creating its own pattern of water use. The types of activities creating this pattern can be categorised into land use-based groups: residential, industrial, commercial, municipal/institutional and other. The way in which water is distributed among these land uses for three Australian cities is shown in Table 26. (For comparison, average US figures are also given.) It can be seen that residential water use accounts for half or more of total water use in urban areas. Furthermore, up to 70% of water used in urban areas is for non-potable purposes, although all water supplied is generally of potable standard (Newman and Mouritz 1996).

Table 26: Urban water use by land use category.
Land use category Percentage of total annual use
  Sydney Brisbane Ballarat Adelaide Perth US average
Residential 65 57 53 70 67 45
Industrial 14 13 22 10 3 27A
Commercial 10 18 5 6 11
Municipal/institutional 6 5 5 15 19A 14
Unmetered/other 5 7 15 0 14

AValue for combined categories.

Source: Shipton et al. (1999); Linsley et al. (1992).

Domestic water use

The total water use of a household is influenced by many factors, the most significant being the number of occupants, income per capita, water price and climate (Gallagher 1980). The quantity of outdoor water use is also affected by garden size. Generally, outdoor use increases from the more densely settled city centre to more spacious suburban areas (Duncan 1991). Urban water use in Australian cities shows a distinct seasonal cycle, as it does in many cities throughout the world. The seasonal increase in water use is primarily due to the increased outdoor water use, particularly for garden irrigation. There is little variation in indoor water use throughout the year (Water Authority of West Australia 1987). Therefore in WA, the base winter level is assumed to be due solely to indoor use, and all water use above this level is taken to be outdoor use.

Domestic water consumption has increased significantly over the last 30-40 years because of increased population and per capita use (Crabb 1997). Rise in per capita use is in part due to the adoption of water-using appliances such dishwashers, but their replacement will almost certainly be with more water-efficient models, resulting in a reduction household water use.

During the 1990s however, there appears to have been a downward trend in household water use in major urban areas (Figure 35). Average daily per capita household water use in major urban areas decreased slightly, from 278 L in 1993-1994 to 253 L in 1999-2000, a 9% decline over six years. This period is one in which there was significant reform in the water industry, as well as an increase in consumer awareness about water conservation through demand management campaigns. It is important, however, that changes in domestic water consumption be checked against climatic patterns and water restrictions that may have prevailed. For example, Central Highlands Water (Ballarat and surrounding areas) experienced drought conditions during the 1996-97 to 1999-2000 period. The height of the drought was the summer and autumn of 1996-97, leading to the high rates of water use during that year (G. Finlay, pers. comm., 2000). In 1997-98 it was drier than 1998-99, which is reflected in the downward trend in water use. In addition, consumer awareness about the drought conditions and need for water conservation grew through the three-year period. But, the total annual rainfall for 1999-2000 was lower than the three previous years and water use in the Central Highlands Water region rose accordingly. In most cases, per capita household water use in 1998-99 was less than the preceding year, which WSAA (1999) attributed to the end of an El Nio event and consequent higher rainfalls.

Figure 35: Average per capita household water use for major urban areas. [HS Indicator 2.2]

 Average per capita household water use for major urban areas

Source: WSAA (1999)

Brisbane is the one major urban area that exhibited a marked reduction in per capita water use from mid-1990s levels, a result of the introduction of the current two-part tariff pricing regime. In the Hunter region, pricing reforms in the early 1980s were followed by a sharp decline in per capita use. Melbourne's decline in per capita use since 1990-91 has been attributed to general consumer awareness along with falling demand in the industrial and commercial sectors. The trends in per capita use, combined with slow population growth, have enabled investments in new water developments to be deferred by as much as 30 years in these metropolitan regions. The situation is quite different in the 'sun-belt' regions of Western Australia and south-eastern Queensland, where the population is growing rapidly (AATSE and IEAust 1999). In those regions, pricing and conservation initiatives by the water authorities, such as Gold Coast City Council, are seeking to reduce consumption and forestall construction outlays on new catchment infrastructure.

Table 27 presents data on residential water use in terms of volumes per household and the total amount of water supplied by the major urban water authority for residential use. Average household occupancy is also given. There appears to be little relationship between household occupancy and household water use between different urban water authorities. Other factors such as climate, level of water conservation practices, demand management campaigns and price may well be stronger determinants of household water use between urban areas throughout Australia.

Table 27: Household water use for major urban water authorities, 1999-2000. [HS Indicator 2.2]
Water authority Average occupancy (persons) Household water use
(L/per/d)A
Total household water use
(GL/y)
ACT Electricity and Water Corporation 2.9 277 35
Barwon Water (Vic) 2.4 230 21
Brisbane City Council (Qld) 2.6 251 78
Central Gippsland Water (Vic) 2.6 244 12
Central Highlands Water (Vic) 2.4 254 10
City West Water (Vic) 2.0 390 15
Coliban Water (Vic) 2.4 225 33
Gold Coast Water (Qld) 2.4 252 13
Gosford City Council (NSW) 2.1 414 14
Goulburn Valley Water (Vic) 2.5 573 39
Hobart Water (Tas) 3.0 178 30
Hunter Water Corporation (NSW) 2.5 264 55
Melbourne consolidated (Vic) 2.9 231 131
Power and Water Authority - Darwin (NT) 2.6 240 113
SA Water Corporation - Adelaide 2.7 240 299
South East Water Limited (Vic) 3.5 361 14
Sydney Water Corporation (NSW) 2.5 298 114
Water Corporation - Perth (WA) 2.8 241 352
Yarra Valley Water (Vic) 2.6 332 168
All major urban areas 2.7 262 1 245

A Litres per person per day.

Source: Modified from WSAA (2000).

Components of domestic water use

Household water use can be separated into indoor and outdoor use. Indoor use can be divided into kitchen, bathroom, laundry, and toilet components. The division of household water use into indoor and outdoor components helps understand how water is used in the domestic sector. The characteristics of indoor and outdoor use are quite different; in particular, indoor use is fairly constant throughout the year, while outdoor use is highly seasonal.

Figure 36 presents reported data for household water use in a majority of Australian capital cites. This graph illustrates varying indoor water use between these capital cities. However, there is a low degree of confidence in such data sets because of the limited number of studies that have collected observed water use data. As a result, assumptions are often required in order to prepare estimates of household water use components. For example, the Sydney values are based on figures from the 1985 Perth study (MWA 1985) but the outdoor water use is modified to more accurately reflect Sydney use (Crabb 1997). There is, however, prima facie evidence to suggest a link between higher levels of residential density in Sydney and Melbourne and lower outdoor use of water.

Figure 36: Components of average household water use in selected capital cities. [HS Indicator 2.2]

 Components of average household water use in selected capital cities

Sources: ACTEW (1994); Jeppesen and Solley (1994); White (1994); South Australian Water (1996); Higgs and Gould (2000); WSAA(2000)