You really have to hand it to Arizona: Even as its population has doubled and it has suffered through a decades long megadrought, the state uses less water today than it did 40 years ago.

This success story is the result of what may be the smartest, most conservative approach to water in the country. But homebuilders want to scrap some key elements of this careful system. It’s a bad idea, especially as the climate changes, making the state’s water supply less reliable. And it’s a cautionary tale for the rest of us as we try to adapt to a warming world.

In 1980, alarmed at watching its precious groundwater disappear amid rapid development, Arizona passed the Groundwater Management Act. The law established the Arizona Department of Water Resources, set up water-management zones around cities and required new housing developments to prove they had access to 100 years’ worth of clean water, among other things.