About 236 million cubic metres of water could be saved annually by 2030 under planned measures to conserve precious water resources and reduce the city's reliance on Dongjiang water imports.
The measures will range from making showerheads more water efficient to reducing leakage from underground pipes and expanding the use of seawater for toilet flushing.
The figure of potential saving, amounting to about a quarter of the total use last year, was released yesterday as the Water Supplies Department unveiled a report that outlined the city's water management strategy until 2030.
The report concluded that Hong Kong faced no imminent water crisis under the existing imports arrangement from Guangdong. But there was room for improvement in conservation before expanding supplies from sources such as commercial scale desalination or water recycling.
'There will be sufficient water supplies in the next 20 years, but that doesn't mean we have nothing to do,' said Bobby Ng Mang-tung, assistant director of the Water Supplies Department. 'We need to be prepared from now on to face probable droughts amid climate change and fluctuation of rainfall patterns.'
Between 70 and 80 per cent of the city's water needs are met by Dongjiang water imports, and the rest from local sources. The proportion could fall in the next 20 years if efforts to conserve water locally pay off.
Mr Ng said the public had a key role to play in conserving water and, to that end, the department would roll out a voluntary labelling scheme on water saving devices from next year, starting with showerheads and extending to washing machines later. An efficient showerhead could save up to a third of water consumed by a four-member household when compared to a conventional one, as well as cut the total water bill by an average of 10 per cent.
It was projected that up to 100 million cubic metres of water could be saved by 2030 if 40 per cent of water devices carried the water efficient labels. Officials said they would not rule out making the scheme mandatory.
Seawater supplies for toilets will also be phased in for Disneyland, Pok Fu Lam, Yuen Long, Tuen Mun and Tin Shui Wai - which could eventually save up to 30 million cubic metres of fresh water a year.
A HK$19 billion programme to replace 3,000km of underground mains would also help save up to 85 million cubic metres by 2030.
Another 21 million cubic metres could be conserved by reusing treated waste water for selected locations.
Mr Ng said it was not an option now to increase water bills to encourage conserving water, even though tariffs have not been revised since 1995.
As for desalination, after a trial the department completed last year, Mr Ng said further studies were needed on how to overcome problems such as the massive amount of energy required for the process.
The trickle-down effect
Tips and the amount of daily water saved per family of four people
Cut shower by 2 minutes 96 litres
Turn off tap while brushing teeth, soaping hands and shaving 26 litres
Wash vegetables and fruit in basin, instead of under tap 14 litres
Wash dishes in basin, instead of under tap 28 litres
Wash clothes with full loads on alternate days, instead of 1/2 loads daily 20 litres
Take showers instead of baths (assume one bath by each per person per week) 44 litres
Total amount of water saved per family: 228 litres
Average daily water consumption: 520 litres
Source: Water Supplies Department