Why we need to explore our water supply options

Hong Kong has built numerous reservoirs and reached costly agreements with Guangdong to pipe water here to secure a reliable supply. Now, desalination has emerged - for the second time - as a possible alternative.

In the 1970s, a desalinator was built in Lok On Pai, Tuen Mun, amid severe water shortages. But the oil-fuelled plant was shut down in 1982 because of high operating costs, and demolished in 1991.

Two decades on, a pilot study by the Water Supplies Department has found that using the much cheaper technology of reverse osmosis to make seawater drinkable is feasible here. The cost of doing so, at between HK$7.80 and HK$8.40 per cubic metre, would still be twice as high as supply from the mainland. If we were to shake free of our dependence on mainland supply, then the price tag for building a large enough facility would be a staggering HK$50 billion.

Those are alarming figures. But they should not cloud our thinking, as we explore alternative means of meeting our daily needs. As Secretary for Environment, Transport and Works Sarah Liao Sau-tung rightly said yesterday, every city had a duty to look at its backup supply, as no one could tell what would happen to clean water sources in the future. All over the world, water has become an increasingly precious resource. It is incumbent on everyone to conserve existing sources of supply and explore new ones.

Even though it is highly unlikely circumstances will ever arise when the mainland turns off the taps supplying Hong Kong, the danger of Guangdong not having an adequate supply to feed us at some point in the future cannot be ignored. China as a whole is not richly endowed with water resources. In the south, supply is plentiful, but pollution is a growing threat. In the arid north, a severe shortage is being tackled by a costly project to divert water from the south. As a coastal city, Hong Kong is being responsible in considering whether we can meet our own demand by turning to the sea.

Cost has to be a factor in deciding whether a desalination facility should be built. At this stage, however, there is no need for us to contemplate replacing our mainland supply with desalinated water. But building a suitable facility to reduce our dependency on the mainland would be a prudent way forward. As Hong Kong is now part of China, the possibility of building a desalination plant in Shenzhen and piping the purified water here should not be ruled out. For a long time to come, the costs of building and running such a facility there will be lower.

Recycled water is another source of supply Hong Kong should seriously look at. For a long time, authorities in California and north Virginia have channelled purified water into underground aquifers and reservoirs respectively. In Singapore, 1 per cent of supply has come from recycled water since 2003. It is time Hong Kong also considered similar moves.