Last summer, as the price of gas inched up over $4 a gallon, Toyota dealers couldn’t keep fuel-efficient Priuses in stock. We should apply that pricing lesson if we want to conserve water, using increasing block rates to discourage profligate water use. Tucson does that and adds a surcharge for excessive use in the summer, when water mostly goes to fill swimming pools and irrigate landscaping.

The idea of charging for water offends many people who think that would be like charging for air. Is it immoral to extract fees for an essential resource? Precisely because water is a public — and exhaustible — resource, the government has an obligation to manage it wisely.

Think of our water supply as a giant milkshake, and think of each demand for water as a straw in the glass. Most states permit a limitless number of straws — and that has to change.

Bottom Line: Higher prices for water that we get from the tap, restrictions on the water we take from the ground, trade among those who have rights — that’s how we should manage water if we want reliable (sustainable) supplies.