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Report Details

Committee Name:

Ecologically Sustainable Development Committee (1997 - 2001)


Legislative Council
Report Type:Report


The Quality of Perth's Water Supply
Report No:9
No of Pages:111
Physical Location:Legislative Council Committee Office

Presentation Date:


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Hide details for Executive Summary and RecommendationsExecutive Summary and Recommendations


1.1 The Sydney water scare of 1998 alerted the Australian public to the danger of water contamination by pathogenic organisms. Fortunately for Sydney residents, no serious disease other than diarroheal illness was reported. However, the legacy of the scare was a meticulous review of all State and Territory drinking water supplies, particularly in view of the enormous financial cost ($75 million) to the Sydney Water Corporation.

1.2 Against this background the Ecologically Sustainable Development Committee (“Committee”) explored whether a potential for a similar scare could occur in Perth. As a result of its investigations, the Committee reassures Western Australians that they may have confidence in the system managing and operating Perth’s water supply. It is highly unlikely that contamination of the type which occurred in Sydney could occur in Perth under current circumstances.

1.3 The inquiry's terms of reference reflect what the Committee considers the key components of ensuring a high quality water supply, that is, an adequate monitoring system; measures to prevent contamination; being able to detect and deal with identified risks; as well as mechanisms for reporting to Government and consumers.

The operation, management and protection of Perth’s water

1.4 The Water and Rivers Commission (“Commission”) is the custodian of all Western Australian rivers, lakes, wetlands, estuaries, inlets and underground water. A key objective of the Commission is to provide for the conservation and enhancement of water quality and environmental values, but at the same time, support sustainable use. To achieve this objective, the Commission uses various policies, guidelines, water protection notes and by-laws as the foundation for plans that protect water quality in underground water pollution control areas, water reserves and catchment areas.

1.5 The Committee appreciates that many other agencies protect Perth’s drinking water quality. For example, the Health Department of Western Australia (“Health Department”) applies the 1987 Australian Drinking Water Guidelines to water providers’ licences. The Advisory Committee for the Purity of Water, established in 1925, provides a non-statutory, independent, monitoring and advisory role to the Health Department, thereby protecting water supplies. The Western Australian Planning Commission, through its State Planning Strategy and other land planning processes, also contributes to water quality protection. The Water Corporation contributes significantly to water quality protection through its commercial interest in a pristine water supply. In 1995, it inherited from the disbanded Western Australian Water Authority, responsibility for operating the infrastructure used to supply Perth's water.

1.6 The Water Corporation prepares water source protection plans for the Perth region supply under delegation from the Commission. The Commission retains overall responsibility for those plans and checks that they identify sources of contamination and set programmes to establish the level of protection required in underground water pollution control areas, water reserves and catchment areas. The Commission attaches a ‘priority system’ P1, P2 or P3 to the plans.

1.7 Priority 1 (P1) areas are declared over land where the provision of the highest quality public drinking water is the prime beneficial land use. Priority 2 (P2) areas are declared over land where low intensity development (such as rural) already exists. Priority 3 (P3) source protection areas are defined to manage the risk of pollution to the water source. P3 areas are declared over land where water supply sources need to co-exist with other land uses such as residential, commercial and light industrial developments.

1.8 The Committee encountered difficulty obtaining the status of protection plans for the Perth metropolitan region. It appears that plans for non-metropolitan areas, which do not contribute to the Perth water supply system are either completed or in a more advanced state than that of metropolitan water source protection plans.

1.9 The Committee notes that the Commission’s endeavours to update existing by-laws governing activities in public drinking water source areas, have been protracted. Reform of the by-laws is needed to align country and metropolitan by-laws for the protection of water quality to both surface and groundwater sources. Progress on the proposed 1997 by-laws is only at the stage where trial catchments have been identified.

Cryptosporidium and Giardia

1.10 Cryptosporidium parvum and giardia lamblia were the culprit organisms responsible for the Sydney water scare. Fortunately, these organisms are not a problem for Western Australia. Water Corporation tests on drinking water sources throughout the State during 1999, contained negligible numbers of cryptosporidium and no giardia.

1.11 Typically, contamination from these pathogenic organisms would be identified after an outbreak of illness, for example as occurred in Milwaukee, USA in 1993 when 400,000 people experienced intestinal illness and 50 people died. The Sydney water scare was unique in that routine monitoring caused the first response, that is, a 'boil water alert' for the Sydney area.

1.12 Ultimately, the Sydney Water Inquiry reported that it was most unlikely that any person suffered illness through ingesting cryptosporidium and giardia. This indicates that given the worst possible scenario of detectable protozoa within a single, poorly managed catchment area such as Sydney’s Warragamba Dam, not one illness was attributable to the water supply itself.

1.13 Pathogenic organisms are not the only means of contaminating water. Various activities in water catchment areas such as illegal firewood cutting, drug crops and vandalism; recreational activities like camping, trail bikes and horse riding as well as commercial logging activities can be contaminating. Organic and inorganic chemicals, pesticides and herbicides further contaminate water.

Perth’s Water Resources

1.14 The Committee notes that less than 4% of Perth’s household scheme water is actually consumed as drinking water. Fifty eight per cent of scheme water is used indoors and 42% outdoors. Of the indoor usage, 22% is used in the bathroom, 19% in toilets, 13% in the laundry and 4% in the kitchen.

1.15 Perth’s scheme water is drawn from both ground and surface water sources. Approximately 47% is sourced from groundwater, the remainder from dams. These statistics underlie the value of Perth’s groundwater supply and the imperative to protect this source. Currently the Gnangara Mound is the major groundwater source for Perth's drinking water and its most important water source.

1.16 It appears that Western Australia’s low population density, small industrial base and good land planning has prevented extensive groundwater contamination occurring. This is significant given that Western Australians rely extensively on groundwater for water supply with our sandy soils making the underlying groundwater highly vulnerable to groundwater contamination, for example, from pesticides. The Committee has recommended that the Health Department’s proposed changes to permitted pesticide use in catchments be subject to public scrutiny and Environmental Protection Authority advice.

Monitoring Perth’s Water

1.17 In practice, it is neither physically nor economically feasible to test for all harmful materials or organisms which may be present in water. However, the Water Corporation conducts extensive testing for its own purposes consistent with the 1996 Drinking Water Guidelines to the most effective level practicable.

1.18 There are deficiencies in the monitoring of Perth's water supply, for example the system is only designed to assess compliance with the 1987 and 1996 Drinking Water Guidelines. The monitoring system provides insufficient information to understand the processes that determine quality of the water, and thus it is almost impossible to anticipate problems before they arise. This is particularly apparent for occurrences of cryptosporidia, giardia, helminth ova and toxicants released by blue-green algae.

1.19 It appears to the Committee that the 1987 and 1996 Drinking Water Guidelines are used in the industry primarily as a focus for compliance-based management strategies without sufficient recognition of the importance of overall system management for assuring safe drinking water. The Committee considers that it is necessary to anticipate and prevent harm in water quality management rather than just react to problems after they arise.

Catchment Management

1.20 During 2000, the Commission began implementing the National Quality Management Strategy through its own ‘State Quality Management Strategy’. A principal focus is ‘integrated catchment management’ with the Commission acting as a facilitator of a process designed to consider the whole water catchment and the interdependence of water quality with land use and management.

1.21 A common thread running through much evidence reviewed by the Committee is that to maintain the quality of Perth's water the first priority should be to protect the water through good land use planning to protect the catchment providing the water, whether surface or ground water. Using treatment to deal with contamination is a second-best option. The Committee found support for adopting catchment protection as the major weapon in preventing contamination of water supplies.

1.22 The Committee accepts that overall, the agencies and authorities managing Perth’s catchments have performed well. However, when the Committee toured Mundaring Weir with the Water Corporation in September 1998, it observed evidence of poor catchment practices. Serious soil erosion from CALM’s softwood logging activities was photographed. In October 2000, it was brought to the Committee’s attention that Stirling Reservoir had been clearfelled to the water’s edge. Such practices have the potential to increase turbidity (murkiness) of water supplies which in turn requires additional chlorination to disinfect. Excessive chlorination in conjunction with organic matter results in increased levels of trihalomethanes in water supplies. High trihalomethane levels are a potential public health issue and by world standards, trihalomethane guideline levels have been significantly relaxed in Australia.

1.23 Under the State Quality Management Strategy, the Commission, the Ministry for Planning and the Department of Environmental Protection have developed an integrated catchment management approach for groundwater mounds around Perth which coordinate and integrate existing legislative instruments without the need for additional legislation.

1.24 Integrated catchment management is based on cooperation between community groups and government agencies at all levels to consider all aspects of catchment management. These groups and agencies then compete for land use from their own perspectives. However, in seeking to accommodate all interests, the Commission is pressured to compromise catchment protection by permitting multiple uses in catchments. This is particularly evident in the context of population and recreational pressures in Perth’s catchments and is of concern to the Water Corporation who see full water filtration treatment, (one part of a multiple barrier system), as the last resort to protecting water quality. The Committee concurs with this view.

1.25 The impetus for pristine water emanates from a health perspective considered by the Minister for Health. This health dominated process clearly has the most significant impact on the quality of Perth’s water because the requirements for public health are more stringent than for environmental management through which the Water and Rivers Commission implements its catchment plans. This necessarily leads to a degree of tension between the objectives of the two regulatory agencies.

Reporting to Government and Consumers

1.26 The Sydney Water Inquiry commented on the absence of a community education program concerning water quality and recommended that the community must have the opportunity to develop an informed understanding of water quality issues and the risks to public health. The Committee endorses that view and could find no such deficiency in the processes by which Perth agencies report to our community. Western Australia is comparatively well placed in having long ago established the Advisory Committee on the Purity of Water to report to the Minister for Health. This has enhanced public confidence in both the monitoring and reporting of water quality data.


Recommendation 1: That the draft by-laws for public drinking water source areas be progressed as a matter of urgency.

Recommendation 2: That water source protection plans for the Perth metropolitan water supply be completed as a matter of urgency.

Recommendation 3: That the protection of water quality to meet public health objectives have primacy in the planning of integrated catchment management.

Recommendation 4: That the review of Public Sector Circular 88 "Use of Herbicides in Water Catchment Areas" be expedited by the Health Department of Western Australia, be the subject of full public consultation, and be assessed by the Environmental Protection Authority.

Recommendation 5: That the Health Department of Western Australia liaise with the National Health and Medical Research Council to review the drinking water guideline level for trihalomethanes.

Recommendation 6: That the Minister for the Environment instruct the Independent Panel of Experts, in consultation with the Water Corporation and Water and Rivers Commission, to recommend guidelines so that logging practices do not affect water quality.

Recommendation 7: That when analytical techniques for the detection of cryptosporidium and giardia are improved, they be incorporated into the Australian Drinking Water Guidelines.

Recommendation 8: That the Water Corporation include water quality issues in its community education programmes.