There seems to be no convincing some people that Aucklanders have nothing to fear from drinking treated Waikato River water. Even the pronouncement by Auckland medical officers of health that the water is safe has not quelled their concerns. They say Auckland should be drawing that water from cleaner sources in the Waitakere and Hunua Ranges. The argument, however, ignores both the reason behind the use of the Waikato River and the world-class treatment that makes water from there safe.

Water from lakes in controlled catchments, such as the Hunuas, is indeed of better quality than that of an unprotected catchment, such as the Waikato River, even if it also needs treatment. But if more dams were built in the ranges, the availability of water would still be subject to drought. That threat is eradicated by supplying water from the Waikato River. Such was the thinking after the debilitating 1994 drought. Nothing since has rendered it invalid.

Equally, water treatment technology and procedures have advanced significantly in eight years. Drinking-water quality, as measured against a standard revised by the Ministry of Health in 2000, has improved appreciably. The Tuakau plant that treats Waikato River water delivers a product that comfortably meets the standard. It boasts modern technology - membrane filters and the like - that could handle far more contaminated water.

Auckland will soon have a high-quality, secure supply. The argument against it holds no water.