Pure water wasted

Moreover, a significant proportion of households live in flats that are not separately metered, so they have little idea of, or concern for, how much water they use (or how much it costs). Flat dwellers tend to believe water shortage is caused not by their consumption but by those who live in houses.

Significant water price rises also have serious equity effects. Doubling the price may have no effect on high-income households but can be onerous for low-income or larger households.

Rather than focus on "big engineering" proposals to increase supply, we should develop measures that encourage (and eventually require) households and businesses to harvest and treat much of their own water. This would require a program to capture and store rainwater for domestic consumption. All new dwellings could be required to install rainwater tanks of reasonable size to supply water for bathroom use. This would not only give households some responsibility but would also provide them with a degree of security in their own supply.

All new dwellings could be required to install greywater recycling systems that store treated water for uses that do not need potable water. An extensive program to retrofit older areas with rainwater tanks and greywater treatment and recycling systems also should be implemented.

Households would become more responsible for the quality of their own recycled grey water and would thus be encouraged to use detergents and cleaning agents that have low levels of phosphate and sodium. That would reduce the amount of these chemicals in sewage and make it easier to treat.

Ultimately, water authorities should be required to deliver a small supply of water to households as their environmental right. But this need not be more than 20 kilolitres a person a year - sufficient to meet their water needs for drinking and food preparation.

Water authorities would thus meet their original remit as suppliers of potable water. They could develop their role as health agencies responsible for sanitation services without using potable water to deliver them.

The ultimate goal is decentralised water supply and sewerage networks that would be vastly more sustainable and secure than the systems that are failing us now.