The "Tuscanisation of Sydney" is being blamed for wasting millions of litres of usable water a year.
Patricia Harvey, chairwoman of the Sydney Coastal Councils group and a Mosman councillor, has witnessed the quarter-acre block with family home and large garden make way for palatial houses, paved parterre gardens, extensive terraces and sweeping expanses of driveways.
Water that was once soaked up by gardens now rushes off hard surfaces, inundates cracked sewers, floods into creeks and eventually ends up in the harbour. "Mosman insists on stormwater retention tanks to slow the flow but it is such a waste of water," Cr Harvey says.
Simon Beecham, the director of water engineering in the faculty of engineering at the University of Technology, Sydney, says most Australian cities waste more water than they use.
"If rainfall falls in the pristine catchments to the south-west of Sydney it is carefully collected, stored in large reservoirs, treated and pumped into Sydney as fresh drinking water.
"If that same rain falls in the Sydney metropolitan area it is allowed to freely pick up litter, sediments, nutrients, bacteria, oils and metals and is often discharged into our rivers, lakes and oceans with little or no treatment."
The city is not only wasting what could be a valuable resource but spending millions a year doing it.
Urban allotments contain about 75 per cent of the hard surfaces that contribute to the stormwater run-off that ends up in streams, rivers and the ocean. The remainder is made up mainly of roads. In response to this councils have set down ratios for the amount of ground surrounding private dwellings that must be able to absorb water.
A NSW parliamentary inquiry into urban water infrastructure last year found the Sydney catchment can absorb up to 90 per cent of the rainfall it receives but this can drop to 10 per cent when land is developed.
Professor Patrick Troy, of the Australian National University's Centre for Resource and Environmental Studies, is to begin a pilot study on types of housing in Sydney and their water consumption.
A study in Adelaide found medium-density housing might raise water consumption. Professor Troy found the per capita water consumption in high rise units was only 10 per cent below that of people who lived in single dwellings with gardens.
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Paving the way to a flood of run-off
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