By Bruce Threlfo
Most of Sydney's water comes from Warragamba Dam. Built in the 1960s, it contains about 70% of the capacity of Sydney's reservoirs. The remaining capacity is in nine smaller dams.
Sydney's water consumption has trebled since 1948. This is partly due to increased population, but per capita consumption has increased by about 66% over this period. Residential consumption accounts for 60% of total consumption.
Warragamba Dam substantially increased Sydney's water supply, and water restrictions have not been required since it came into operation.
Two options are being considered to increase supply. One is to augment Warragamba Dam, which could treble the supply capacity. This would involve two stages, the first being a flood mitigation dam. The Warragamba proposals could cost up to $350 million.
The other option is the construction of the Welcome Reef dam on the Shoalhaven River, south of Goulburn. This would double the supply capacity and cost about $140 million.
Major are problems associated with both proposals. The Warragamba augmentation would have significant impacts on the Nattai and Kanangra-Boyd national parks, which are part of the Blue Mountains area proposed for world heritage listing. The region contains the largest temperate eucalypt wilderness in the world.
The Welcome Reef dam would also flood some areas of conservation value that support animal species of rare or restricted status. However, its major problem could be outbreaks of blue-green algal blooms caused by phosphate run-off from the catchment area combined with low flow conditions. This creates the risk of contamination of Sydney's water supply on a massive scale.
The alternative to building more dams is to reduce
consumption. Various measures to reduce water usage (low flush toilets, efficient appliances) could be installed in new and existing buildings. There are no regulatory requirements for water-efficient appliances, and the Sydney Water Board does not offer incentives for their use. A National Water Conservation Rating and Labelling Scheme, which was launched in 1992, is only a voluntary scheme.
Pricing is now being touted as a significant means of reducing consumption. However, a "user pays" approach for water pricing raises concerns that low income earners and large households will be disadvantaged. The introduction of consumption-based water rates should be accompanied by measures which give consumers access to water-efficient appliances as well as providing means for much greater recycling of "grey water" for garden and industrial use.
There are other areas of policy which can reduce costs to consumers. It has been Water Board policy to have sufficient storage capacity such that water restrictions are not required more frequently than one year in 30. A reduction in this standard to one year in 20 would defer construction of the Welcome Reef dam for 15 years, providing more time to introduce alternatives to more dams.