From the article: "Reducing waste seems like an obvious solution to overuse, but it can actually make the problem worse. Bradley Udall, a scientist at Colorado State University’s Colorado Water Institute—his family has been prominent in conservation and in regional and national politics for decades—told me that water use can be divided broadly into two categories: consumptive and non-consumptive. When a farmer irrigates a field with river water, he said, some of the water is consumed by whatever the farmer is growing and by evaporation, but some is returned to the stream. The ditch system in the Grand Valley carries runoff and surplus irrigation water back to the river, and that water is used again, mainly by other farmers. (Kent Holsinger told me that, on average, river water is used more than half a dozen times before it leaves the state.) Excess irrigation water also soaks into the earth, replenishing groundwater and, eventually, feeding surface streams."
"Waste, paradoxically, is a kind of reservoir. If the residents of a suburb routinely water their lawns, they can stop during a drought. But once they’ve replaced their Bermuda grass with cacti and gravel, and once the water that formerly ran through their sprinklers has been redirected to bathrooms and kitchens in brand-new subdivisions, the enlarged system is more vulnerable in dry periods, because it contains less slack."