State of the Environment Report 2007
Water is a fundamental resource for human settlements: it is critical to human survival, health and wellbeing; facilitates economic development; and provides social and recreational benefits. Water service provision is necessary in settlements to provide clean water for drinking, cooking, cleaning and for removing wastes. This issue focuses primarily on water used by households, while the broader water supply sector is addressed in 'Towards Sustainability'.
Approximately 1800 gigalitres (GL) of water are used annually in WA, of which 18% is consumed directly by the household sector. Around 70% of household water comes from the Integrated Water Supply Scheme, and 30% from domestic bores. Households are indirectly responsible for water use in manufacturing and agriculture (particularly irrigated crops), as these sectors produce food (such as dairy, fruits and vegetables) and manufactured goods (such as paper products and cotton garments) consumed by households. Water use for public parks and gardens, around 4% of total water use in WA, can also be attributed indirectly to households. People in urban settlements are also responsible for a significant share of water demand in the services industry, especially in relation to restaurants, cafes and hotels.
Increasing demand for water for settlements puts greater pressure on limited water resources through excessive abstraction of surface water and groundwater sources and eventually results in environmental degradation. Wastewater from households is either connected to public sewerage systems or discharged into septic tanks or other onsite treatment and disposal units. If onsite wastewater treatment units are not properly installed or maintained, they can pose a threat to public health and local receiving environments.
Public scheme water supplies have historically been sourced from a mixture of groundwater (approximately 55%) and surface water (approximately 45%) sources. In November 2006, the Kwinana seawater desalination plant commenced operations and currently contributes approximately 17% of annual demand from the Integrated Water Supply Scheme which supplies Perth, the Goldfields and the South West. Total residential consumption of scheme water has fluctuated between 192 and 231 GL since 1996 (Figure HS3.1). In 2005-06, residential consumption of scheme water was 211 GL. Initiatives of the State Water Strategy (Government of Western Australia, 2003) may have contributed to the stabilisation of household scheme water use since 2004.
The total number of domestic bores in the Perth metropolitan area in 2004 was about 140 000, representing 24% of all households in Perth (Australian Bureau of Statistics, 2004c). In some suburbs of Perth (including Morley, Applecross, Bullcreek and Rockingham), more than 75% of houses have garden bores (Water and Rivers Commission, 1997). In 2003, approximately 11% of households outside Perth used bore water (Australian Bureau of Statistics, 2004c). Accurate data on household bore water use are not available because domestic bores are not metered, but it is estimated to average 800 kilolitres (kL) per bore per year in the Perth metropolitan area. This water is used almost exclusively to water gardens. In 2003-04 total bore water use in Perth was around 112 GL, representing 23% of total groundwater abstraction in this area (Davidson & Yu, 2004). Garden bore abstraction is projected to continue to increase at the rate of 3-4 GL/year.
![Figure HS3.1: Total and per capita residential water use in Western Australia, 1996–2006. [Data source: Water Corporation. Note: These data only include water supplied through the Integrated Water Supply Scheme directly to the household sector by the Water Corporation. It excludes Bunbury and Busselton, remote communities, mining towns and small communities whose scheme water schemes are run by local authorities. It also excludes household water use from private bores.]](/site/files/images/Figure-HS3.1_Large.jpg)
Average residential consumption of scheme water per person decreased between 2000-01 and 2005-06 from 142 to 114 kL per person (Figure HS3.1). Residential water use per person varies considerably among settlements throughout the State (Figure HS3.2), and is highest in the North West. Until around 2001, water supply capacity in this region was considered to significantly exceed demand and there was little urgency to implement demand management measures. Since this time there has been a growing need to manage pressure on North West water resources due to increased demand, particularly from growth in the mining sector. Most of the southern half of the State (Perth, South West, Peel and the Agricultural and Mid West regions) increased scheme water usage in 2003-04, highlighting the sensitivity of this part of the State to warmer summers, as occurred in 2003-04. However, residential water use per capita has generally declined in the southern half of the State since 2000-01.
![Figure HS3.2: Trend in average per capita water use in Western Australia, by settlement and region, 1998–2004. [Data source: Water Corporation; Analysis: EPA; Presentation: EPA. Note: These data only include water supplied through the Integrated Water Supply Scheme directly to the household sector by the Water Corporation. It excludes Bunbury and Busselton, remote communities, mining towns and small communities whose scheme water schemes are run by local authorities. It also excludes household water use from private bores.]](/site/files/images/Figure-HS3.2_Large.jpg)
Although high quality potable water sources are used to supply public drinking water supply schemes, only a tiny fraction of this water is actually used for drinking or cooking (Figure HS3.3). A survey of household water use in Perth in 1999-2000 indicates that outdoor use represents 56% of the total water consumption of a typical single residential household, which requires little treatment compared to that for drinking (Loh & Coghlan, 2003). Nearly all of this (97% or 687 L/day averaged over a year) is used to water gardens, and a further 3% (20 L/day) is used for swimming pools. Baths and showers, clothes washing, and toilet flushing account for most indoor water use. The proportion of water used for different purposes may have changed since the survey was conducted due to the introduction of water restrictions in 2001.
According to the survey, multi-residential households (e.g. townhouses, villas, flats) use 40% less water on average than single residential households although this does not include water use in common areas for multi-residential households (Figure HS3.3). This is due in part to smaller household sizes, but mostly to smaller garden areas per household. Multi-storey apartments are generally the most water-efficient form of housing.
It is difficult to determine exactly how much indirect water demand can be attributed to households, but it is likely to substantially exceed the water used directly by households.
![Figure HS3.3: Average water use in Western Australian households in 1999–2000. [Data source: Loh & Coughlan (2003).]](/site/files/images/Figure-HS3.3_Large.jpg)
Reuse of treated water from municipal wastewater systems reduces pressure on receiving environments and the demand on groundwater and surface water resources. Reticulated wastewater systems (deep sewerage) are the most common method of household wastewater disposal in WA. Wastewater is piped to centralised treatment plants, where contaminants are removed or neutralised to levels such that the treated wastewater can be safely discharged to the environment or diverted for reuse. However, treated wastewater can still contain significant levels of pathogens and requires higher levels of treatment to be considered safe for drinking.
For coastal communities, where urban populations and growth are concentrated, marine disposal of treated wastewater is considered an environmentally safe and sustainable method of disposal, due to the extensive receiving environment and its considerable absorptive capacity. For inland settlements, disposal of treated wastewater into waterways is often constrained by eutrophication (nutrient enrichment) problems.
Between 2001-02 and 2004-05 the proportion of wastewater generated in WA that was reused remained fairly constant as around 10%, with development of new wastewater reuse projects being just sufficient to keep pace with population growth. In 2005-06, the proportion of wastewater reuse increased slightly to 11.5% due largely to the commencement of the Kwinana Water Reclamation Plant. The plant produces around 16 megalitres per day of high quality water from secondary treated wastewater for industrial use in the Kwinana area.
Non-metropolitan areas reuse a higher proportion of wastewater than Perth: about 40% compared to 5% (Figure HS3.4). This is due partly to the larger number of opportunities for large scale reuse in rural areas such as irrigation or heavy industry.
![Figure HS3.4: Trends in wastewater reuse in Western Australia by region, 2001–02 to 2005–06. [Data source: Water Corporation. Note: Includes townships within the Water Corporation’s wastewater service area, including Bunbury and Busselton. Excludes remote communities, mining towns and small communities whose sewerage schemes are run by local authorities.]](/site/files/images/Figure-HS3.4_Large.jpg)
Connecting households to sewerage is important for preventing contamination of local groundwater and eliminating threats to public health from on-site effluent disposal systems. There has been a steady increase in the proportion of households connected to sewerage compared to the number of connections available. This trend is due to the Water Corporation's ongoing Infill Sewerage Program in established urban areas. Despite this some areas have comparatively low rates of connection to sewerage, most likely because connection is not enforced on households. Perth has the highest rate of sewerage connection compared to other regions in WA (Figure HS3.5).
![Figure HS3.5: Trends in household connection to sewerage in Western Australia by region, 2002–03 to 2005–06. [Data source: Water Corporation. Note: Includes townships within the Water Corporation’s wastewater service area, including Bunbury and Busselton. Excludes remote communities, mining towns and small communities whose sewerage schemes are run by local authorities. South West may be artificially low due to differing method used to calculate percentage connections.]](/site/files/images/Figure-HS3.5_Large.jpg)
Population growth is putting considerable pressure on water resources and driving an increase in the volume of wastewater generated. This increases pressure to find new environmental water supplies and expand existing ones. It also requires significant new infrastructure for water treatment, delivery and wastewater removal, and often competes with other sectors and the environment for available water resources. Viable opportunities for wastewater reuse schemes are limited, particularly in Perth and other large urban centres. As population grows, there is mounting pressure to find and exploit new reuse opportunities, and continue improvements in demand management, reuse and source-substitution programs.
The average household size in WA has been declining since the 1960s. Smaller households place greater pressure on per capita water demand, particularly as water consumed for garden watering (the highest use category) is independent of the number of persons living in the household.
Our aspirational culture and increasing affluence are placing increased pressure on per capita water consumption, particularly through higher expectations of garden appearance, and increased desire for labour saving appliances and fittings. For example, dishwashers use more water than hand washing in the sink, automatic washing machines use more water than twin-tubs or other non-automatic machines, and households with automatic reticulation use almost twice as much water on their gardens as those with no automatic reticulation. The use of appliances and fittings has become far more commonplace over recent decades (Table HS3.1). Most significant among these is the sharp increase in the proportion of households using automatic reticulation systems, up from 2% of households in 1981-82 to 25% in 1998-00. This trend is expected to continue.
Water restrictions, community education and rebate schemes (to encourage use of water efficient fittings and appliances) are helping to reduce household water demand whilst maintaining lifestyle and cultural expectations. However, there is a limit to how much can be achieved with these measures. For example, the potential for gains in water use efficiency diminishes as more households are retrofitted with water efficient devices. Eventually, to further reduce per capita water consumption, it may be necessary to challenge lifestyle and cultural expectations, such as the desire for expansive lawns and exotic garden species.
Long-term rainfall data from the South West indicates a 10-20% decline in rainfall over the past 30 years, manifested as a sudden shift towards a drier climate (from Geraldton to Esperance) in the mid-1970s (Indian Ocean Climate Initiative, 2002). This has produced a 65% decline in environmental water availability. Modelling by CSIRO (2001) suggests that this trend of declining rainfall will continue, and is also likely to impact on water availability in the Gascoyne-Murchison and Goldfields regions. In addition to reduced recharge of water sources, higher average temperatures are likely to increase direct demand from the household sector to maintain lawns and exotic gardens, and increase demand from the agriculture sector to maintain productivity.
State Water Plan: was developed to ensure the strategic and effective management of water resources using a whole of water cycle approach (Government of Western Australia, 2007).
State Water Strategy: was developed to improve water demand management and water use efficiency within the household sector (Government of Western Australia, 2003). Initiatives include a rebate scheme to encourage use of water efficient fittings and appliances in homes. The rebate incentive scheme has proved successful with 197 627rebates made between February 2003 and June 2005 for water efficiency products which have saved an estimated 6.7 GL of water per annum. Daytime sprinkler bans for households and public parks and reserves have also been implemented, and household sprinkler use has been restricted to two days per week for households served by the Integrated Water Supply Scheme.
Waterwise program: This includes certification programs for industries that service the household sector, including plumbers, garden centres and garden irrigators. These programs have been well received, with 117 separate providers accredited and participating. The Waterwise Schools program targets water use efficiency within schools and provides comprehensive teaching materials and education programs across all areas of the curriculum. As at February 2006, 305 schools were participating in the program.
Wastewater recycling: The Kwinana Water Reclamation Plant will be upgraded to a total capacity of 9.6 GL per year in coming years, which is equivalent to approximately 8.3% of Perth's current wastewater production.
Planning tools: The Department for Planning and Infrastructure is developing a WA version of BASIX. This web-based planning tool allows designers of new houses to achieve reductions in water and energy use compared to calculated benchmarks. The department is also giving consideration to a similar tool, Retrofix, for existing homes.
Water use and availability, and wastewater reuse are emotive and contentious issues for many WA settlements. Water use is expected to continue to grow as new water sources are required to meet increasing demands of a growing and more affluent population. The volume of wastewater generated will also increase and pose further eutrophication (nutrient pollution) related challenges for receiving environments. Climate change will result in some parts of WA becoming hotter and drier, thereby increasing water usage and putting additional pressure on environments where water is extracted. Water reuse, recycling and climate-independent water supplies (e.g. desalinisation) will become more important in these areas. Increased demand for high quality water sources will require new infrastructure development, using more economically marginal water sources than have historically been developed. Consequently, this will place upward pressure on the cost of household water services. Growing demand from the household sector will also increase competition with other sectors for scarce water resources, which is likely to constrain productivity or economic growth.
7.13 Continue to implement the State Water Strategy and the State Water Plan: both are in the early stages of implementation.
7.14 Implement BASIX in the development of new residential buildings and promote Retrofix for established buildings.
7.15 Implement Western Australian Sustainable Cities initiatives.
7.16 Expand research and implementation of water recycling at planning, subdivision and individual building scales.
7.17 Licence domestic bores.
