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1367.5 - Western Australian Statistical Indicators, Jun 2004  
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Contents >> Environment >> Household water conservation and use in Western Australia

Household water conservation and use in Western Australia
This article was published in the June quarter 2004 issue of Western Australian Statistical Indicators (ABS Catalogue Number 1367.5)


INTRODUCTION

Water is a crucial resource for Western Australians in terms of maintaining public health, facilitating economic development and preserving the environment. Recent drought conditions in this state have brought into focus the need to ensure a sustainable water future for Western Australians. The Government of Western Australia's (GovtWA) State Sustainability Strategy defines sustainability as 'meeting the needs of current and future generations through an integration of environmental protection, social attachment and economic prosperity' (GovtWA 2003a). One important factor in achieving sustainability is ensuring that there is an appropriate balance between supply of, and demand for, water resources to meet both current and future needs.

Current state government policies aimed at ensuring the sustainability of Western Australia's water resources are outlined in the State Water Strategy (GovtWA 2003b). One of the key objectives of the strategy is water conservation across all sectors of water use. Water conservation includes activities designed to reduce the demand for water, by improving efficiency in use and by reducing losses and waste of water. Water conservation falls on the demand management side of the sustainable water use equation, and balances the requirement for new source development to maintain or increase supply.

This article examines current and future trends in the supply of, and demand for, water in Western Australia and provides a snapshot of water conservation and use by Western Australian households.


SUPPLY OF WATER

Western Australia's water supply is made up of surface water and groundwater sources. Surface water comes from open bodies of water such as streams, rivers, lakes or reservoirs, whereas groundwater occurs below the land surface. A large proportion of the total volume of water in these sources needs to remain there in order to preserve the environment. Through the Water and River Commission's (WRC) water allocation process, nearly 90% of surface water is set aside for the environment and significant volumes of groundwater are reserved to protect groundwater dependent ecosystems (WRC 2000). The proportion of water that is leftover is the amount that can be sustainably extracted from the environment for use by Western Australians.

The largest public water supply scheme for households in Western Australia is the Integrated Water Supply Scheme (IWSS), operated by the Water Corporation (WC). It services approximately 78% of the state's population and covers Perth, Mandurah, Pinjarra, towns and properties along the Goldfields pipeline to Kalgoorlie-Boulder, and extensions of the pipeline into the surrounding agricultural areas (GovtWA 2003b) (ABS 2004a). Surface water and groundwater sources each supply about half of the water used in the IWSS (WC 2003b).


IMPACT OF CLIMATIC CONDITIONS

Climatic conditions play an important role in the sustainability of water resources. The amount of water occurring in the environment, and hence the proportion that is available for use, is determined by rainfall levels and the amount of water that subsequently flows into surface water sources and replenishes groundwater sources. Temperature levels, solar radiation and vegetation conditions also impact on water supplies by determining how much water from rainfall is lost through evaporation and by plant transpiration before reaching surface and groundwater sources.

The size and geographical diversity of Western Australia means that there are different climatic patterns across the state. The IWSS draws its water from sources around Perth and other areas in south-west Western Australia. The weather in this region is characterised by cool wet winters and hot dry summers. On average, most of the rainfall in this area (86%) occurs between May and October (Loh and Coghlan 2003).


CURRENT SUPPLY

In 2000, surface water stocks amounted to 857 GL of developed yield - that is the average annual volume of water that could be diverted for use within existing infrastructure. The sustainable yield for groundwater supplies - the amount of water that could be sustainably extracted - was 7,223 GL in 2000 (ABS 2004a). Not all of this water was suitable for human consumption. Desalination technologies can be used to convert more water to drinking water quality, however these technologies can be costly (GovtWA 2003b). The location of some water sources also limits household access, due to the high costs involved in developing the infrastructure required to deliver water to households that are not situated near water sources.

The amount of water available to supply the IWSS has been affected by changing climatic conditions in the south-west region of Western Australia. According to information published by the Indian Ocean Climate Initiative (IOCI), there has been an estimated 0.7oC increase in annual mean temperature over the last 50 years in this region (IOCI 2002b). Although numerically small, the average increase is significant from a climatic perspective. There has also been a 10-20% decrease in average winter rainfall across areas in south-west Western Australia over the last 30 years (IOCI 2002b). According to unpublished data provided by the WC, in Perth for example, the average annual rainfall until 1974 was 882 mm, whereas since then it has decreased to an average of 788 mm. As a result of these changes in climatic conditions, there has been a reduction in the amount of water flowing in streams and therefore into the dams that supply the IWSS. From 1911 to 1974, average streamflows into IWSS dams were 338 GL/year. This reduced to an average of 167 GL/year flowing into dams between 1975 and 2001 (GovtWA 2003b).


FUTURE SUPPLY

The CSIRO forecasts that the south-west of Western Australia will continue to become warmer and drier than last century (IOCI 2002b). As a result, it is likely that the amount of water occurring in the environment in that part of the state, and subsequently the total volume that can be sustainably extracted for use in the IWSS, will continue to reduce in the future (IOCI 2002a).


DEMAND FOR WATER


CURRENT DEMAND

Western Australian water consumption was 1,409 GL in 2000-01 (ABS 2004a). The Agriculture industry was the largest consumer during the period, accounting for 40% of water consumption in the state. Western Australian households were the second largest user of water, consuming 17% of total consumption. The Mining industry accounted for 14% of total water consumption in this period.

WATER CONSUMPTION—2000–01

Graph: Water consumption 2000-01


(a) Includes Sewerage and drainage services.
(b) Includes Cultural and personal services.
Source: ABS 2004b, Water Account, Australia (cat.no. 4610.0).


FUTURE DEMAND

Water demand projections based on expected industry and population growth, and assumptions about how this will translate into demand for water, suggest that water consumption in Western Australia will grow to 3,500 GL/year by 2020-21 (GovtWA 2003b). The projections assume strong growth for agricultural, mining and manufacturing uses and include approximately 700 GL of water consumption that is dependent on Stage 2 of the Ord Irrigation Scheme proceeding (WRC 2000). Households are expected to remain a major user of water in the state, with water consumption predicted to increase in line with projected population growth (WRC 2000).


BALANCE OF SUPPLY AND DEMAND

Overall, Western Australia has considerable water resources to meet its future needs. There are however, specific water sources, particularly in regions that supply the IWSS, that have reached or are nearing their sustainable limit (WRC 2000). Increasing demand will put water supplies in these areas under further pressure. While there is scope for new sources to be developed to meet current and future needs, these processes will take considerable time, are likely to be expensive and will not be without environmental and social impacts. Given the limitations on new source development, water conservation achieved through the effective management of water demand, will become increasingly important for ensuring a sustainable water future for Western Australians.


HOUSEHOLD WATER CONSERVATION AND USE

Western Australian households currently represent an important sector of water use and are likely to remain so in the future. Household water conservation is therefore an important factor in ensuring the sustainability of the state's water resources. The State Water Strategy sets out a range of policies to reduce demand in the household sector, including regulation of use, financial incentives, pricing policies and community education (GovtWA 2003b). A permanent daytime sprinkler ban has been in place since November 1994 in Perth and other areas supplied by the IWSS. Current restrictions, in place since September 2001, limit sprinkler use to two days per week.

Households access water through public supply schemes (via connection to mains water) and self-extraction methods (such as garden bores, rainwater tanks and farm dams). Western Australian households rely heavily on mains water to meet their needs. In a survey conducted in March 2001, the ABS found that mains water was the main source of bath, shower and washing water for 95% of Western Australian households and the main source of drinking water for 84% of households (ABS 2001). It was also the main source of garden water for 77% of households, however this may since have decreased as a result of the
tighter watering restrictions introduced in September 2001.

The conservation of mains water is a particular focus of the State Water Strategy, given the high quality of the water supply and the substantial infrastructure costs involved in delivering it to households via large-scale public supply schemes. A key target of the strategy is to reduce usage levels for Perth consumers of the IWSS to 155 kL per person by 2012 (GovtWA 2003b). All other public water supply schemes in Western Australia will need to establish similar targets by 2004.

With the introduction of a two day per week watering restriction and additional demand management measures, water use by Perth consumers of the IWSS decreased from 185 kL per person in 2000-01 to 150 kL per person in 2002-03 (GovtWA 2004). However, the challenge is to achieve the water conservation target without the continued imposition of water restrictions. Information from the ABS' Domestic Water Use Survey for Western Australia provides a snapshot of household water conservation and use in October 2003. This information can be used in developing strategies to further reduce water use in the household sector. Unless otherwise stated, figures in the following section were sourced from this survey.


SOURCES OF HOUSEHOLD WATER SUPPLY

By extracting or collecting water directly for their own use, households can reduce the demand on high quality mains water supplies. In October 2003, an estimated 728,900 households in Western Australia (94% of all households) were connected to mains water. Of these, over one fifth (21%) reported using bore water and 8% used water from a rainwater tank.

SOURCES OF HOUSEHOLD WATER SUPPLY - October 2003
Graph: Sources of household water supply - October 2003


(a) All households.
(b) Households connected to mains water supply.
Source: ABS 2004c, Domestic Water Use, Western Australia (cat.no. 4616.5.55.001).


COMPONENTS OF HOUSEHOLD WATER USE

It is useful to understand the components that make up household water use, to enable an assessment of the areas in which there is the greatest potential for conservation of mains water supplies. Data on the components of household water use is available from a study conducted by the WC from November 1998 to June 2000 (Loh and Coghlan 2003). The Domestic Water Use Study covered 120 single residential households located in three suburbs of Perth that received their mains water supply through the IWSS. The data was collected while the daytime sprinkler ban was in place, but before sprinkler use was further limited to only two days per week.

According to the WC study, 56% of the total water used by these households went on outdoor water use, 42% was used indoors and the remainder went on water leaks. Almost all outdoor water use (97%) was accounted for by lawn and garden watering, with the remainder used on swimming pools (mainly for topping up purposes). Small amounts of water drawn from outdoor taps (such as that used for washing hands) were included in indoor tap usage. Use of showers and baths was the largest component (33%) of indoor water use by households in the WC study, followed by use of washing machines (27%) and toilets (21%). Use of taps made up 16% of water use and other components (such as using dishwashers, evaporative air conditioners and indoor spas) together accounted for 3% of indoor water use (Loh and Coghlan 2003).

COMPONENTS OF INDOOR WATER USE - 1998-2000
Graph: Components of indoor water use - 1998-2000

(a) Includes a small amount of water use from outdoor taps.
(b) Includes dishwashers, evaporative air conditioners and spas.
Source: Loh, M. and Coghlan, P. 2003.


OUTDOOR WATER CONSERVATION AND USE

There are a variety of ways in which Western Australian households can reduce their use of mains water supplies outdoors, and hence make an important contribution to water conservation in the state.

In October 2003, the majority (95%) of Western Australian households connected to mains had gardens or lawns and 97% watered them. Most of the garden practices of Western Australian households are still based on northern European style gardens which demand heavy watering (GovtWA 2003b). Of those households with gardens or lawns, over half (53%) used automated reticulation systems for watering. Some types of automated systems (for example manual tap timers fitted to reticulation systems) can help to conserve water because they turn off automatically. Other automated reticulation systems (such as electronic systems) are not necessarily water efficient because there can develop a 'set and forget' mentality among householders. While these systems contribute to water conservation by turning off automatically, they may turn on automatically when there is no need for watering.

The use of mulch, including materials such as wood chips, straw, lucerne, hay and newspaper, in gardens reduces evaporation and hence the need for watering. Over two thirds (69%) of Western Australian households connected to mains that had gardens or lawns used mulch in the twelve months prior to October 2003. Households living in a separate house were more likely to have used mulch (72%) than households in a semi-detached, row or terrace house or townhouse (57%) or households in a flat, unit or apartment (45%).

Of those Western Australian households connected to mains that had gardens or lawns in October 2003, 44% reported re-using water from around the house for the purposes of watering during the previous twelve months. This included a broad range of practices, such as using sophisticated greywater recycling systems, collecting water from running a shower, and pouring leftover water from water bottles and vases onto gardens/lawns.

An estimated 126,600 households in Western Australia (17% of those connected to mains) had a swimming pool or outdoor spa in October 2003. Of all Western Australian households that had a pool/outdoor spa, 30% had a pool/spa cover. Households that use a pool/spa cover can conserve mains water through not having to top up their pool/outdoor spa to compensate for evaporation. In addition, by keeping the pool/outdoor spa clean, the cover can also reduce the need to backwash the filter which can waste water (WC 2003a).

OUTDOOR WATER CONSERVATION AND USE-October 2003
Graph: Outdoor water conservation and use - October 2003

(a) Households with gardens or lawns.
(b) In the last 12 months.
(c) Households with swimming pools/outdoor spas.
Source: ABS 2004c, Domestic Water Use, Western Australia (cat. no. 4616.5.55.001).


INDOOR WATER CONSERVATION AND USE
There are a number of indoor water-using appliances commonly used by Western Australian households that draw on mains water supplies. The efficient use of such appliances can contribute to water conservation in the state.

An estimated 6 kL of mains water per household per year can be conserved by using a water efficient, rather than normal flow, shower head (Loh and Coghlan 2003). Almost two in five (38%) Western Australian households connected to mains had only water efficient shower heads installed in their dwelling in October 2003. Households living in dwellings that were fully owned (42%) or being purchased (39%) were more likely to have only water efficient shower heads than those living in rented dwellings (29%).

More efficient use of washing machines is a means by which households can conserve water. Almost all Western Australian households connected to mains (97%) had a washing machine in October 2003. The majority of these (84%) had a top loading machine, 13% had a front loading machine and the remainder had other types of washing machines. Front loading washing machines are more water efficient than most top loading machines and can conserve an estimated 15 kL of mains water per household per year (Loh and Coghlan 2003). The reason most frequently reported by Western Australian households for choosing a front loading washing machine was 'more water efficient' (66%), followed by 'better for clothes' (36%) and 'more energy efficient' (26%).

A small proportion (4%) of Western Australian households with a washing machine did not use it in the week prior to the survey. People living alone most commonly reported doing 1-2 loads of washing in the week prior to the survey (61%), whereas couple only households, lone parent households with children, and other households most commonly washed between 3-5 loads (49%, 42% and 43% of these households respectively). Couple with children households most commonly washed between 3-8 loads in the week prior to the survey (61%). Some 46,000 households reported doing 12 or more loads of washing (6%).

Since 1982 there has been a mandatory requirement in Western Australia to install dual flush toilets in all new homes and renovations, as they can contribute to household water conservation. Dual flush toilets typically use 12 kL less water per household per year than single flush toilets (Loh and Coghlan 2003). In October 2003, an estimated 526,600 Western Australian households connected to mains had only dual flush toilets installed in their dwelling (72%). Nearly one third (32%) of households in rented dwellings did not have any dual flush toilets, compared with 24% of fully owned dwellings and 17% of dwellings being purchased.

More efficient use of dishwashers is another means by which households can conserve water. The amount of water used by dishwashers varies from the equivalent of two sinks of water per wash for newer, water efficient models to up to 50 L per wash for older models (GovtWA 2003c). In both cases, dishwashers can conserve mains water if they are used with full loads. In October 2003, 29% of Western Australian households connected to mains had a dishwasher. Almost one quarter (23%) of households with a dishwasher did not use it in the week prior to the survey. Close to half (44%) of lone person households with a dishwasher reported not using it in the week prior to the survey, while 41% of couple with children households used their dishwasher 6 times or more.

Evaporative air conditioners use water in the process of cooling the air temperature of dwellings. Almost one quarter (24%) of Western Australian households connected to mains had an evaporative fixed air conditioner in October 2003. Evaporative air conditioning systems with two or less outlets are likely to use less water than those with more than two outlets (typically 'whole of house' systems). Of the estimated 174,800 Western Australian households that had evaporative fixed air conditioning, the majority (85%) had more than two outlets in their dwelling.

INDOOR WATER CONSERVATION AND USE(a) - October 2003
Graph: Indoor water conservation and use (a) - October 2003

(a) Households connected to mains water supply.
Source: ABS 2004c, Domestic Water Use, Western Australia (cat. no. 4616.5.55.001).


CONCLUSION

Water conservation is important in ensuring a sustainable future for Western Australians. Water supplies in the south-west of the state are reducing as a result of changes in climatic conditions, while total demand for water is predicted to increase considerably by 2020-21. While Western Australia has substantial water resources to meet its future needs, decreasing supply and increasing demand are placing pressure on specific water sources - particularly those in Perth and other south-west regions that are drawn on to provide mains water for over three quarters of the state's population via the IWSS. Household water conservation plays an important role in ensuring there is an appropriate balance between supply of, and demand for, water resources to meet both current and future needs. Information from the ABS' Domestic Water Use Survey for Western Australia provides a snapshot of the ways in which households were conserving and using mains water in October 2003. This information can be used in developing strategies to further reduce water use in the household sector.


LIST OF REFERENCES


ABS PUBLICATIONS

Australian Bureau of Statistics 2001, Environmental Issues: People's Views and Practices, March 2001, cat. no. 4602.0, ABS, Canberra.

Australian Bureau of Statistics 2004a, Regional Population Growth, Australia and New Zealand 2002-03, cat. no. 3218.0, ABS, Canberra.

Australian Bureau of Statistics 2004b, Water Account, Australia, 2000-01, cat. no. 4610.0, ABS, Canberra.

Australian Bureau of Statistics 2004c, Domestic Water Use, Western Australia, October 2003, cat. no. 4616.5.55.001, ABS, Canberra.


NON-ABS PUBLICATIONS

Government of Western Australia 2003a, Hope For The Future: The Western Australian State Sustainability Strategy, Government of Western Australia, Perth.

Government of Western Australia 2003b, Securing Our Water Future: A State Water Strategy for Western Australia, Government of Western Australia, Perth.

Government of Western Australia 2003c, Where Does The Water Go?, viewed 11 May 2004, <www.ourwaterfuture.com.au/supply/content_consumption_study.asp>.

Government of Western Australia 2004, Securing Our Water Future: A State Water Strategy for Western Australia: One Year Progress Report, Government of Western Australia, Perth.

Indian Ocean Climate Initiative 2002a, Climate Variability and Change in South West Western Australia, Indian Ocean Climate Initiative Panel, Perth.

Indian Ocean Climate Initiative 2002b, Climate Variability and Change in the South-West, viewed 10 May 2004, <http://www.ioci.org.au/publications/pdf/IOCI_CVCSW02.pdf>.

Loh, M. and Coghlan, P. 2003, Domestic Water Use Study: In Perth, Western Australia 1998–2001, Water Corporation, Perth.

Water and Rivers Commission 2000, Western Australian Water Assessment 2000 - Water Availability and Use, Water and Rivers Commission Policy and
Planning Division, Perth.

Water Corporation 2003a, Being Waterwise, viewed 10 May 2004, <http://www.watercorporation.com.au/savingwater/savingwater_poolcovers.cfm>.

Water Corporation 2003b, Our Water Sources, viewed 10 May 2004, <http://www.watercorporation.com.au/dams/dams_supply.cfm>.


NOTES

kL = kilolitre = one thousand litres

GL = gigalitre = one thousand million litres


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