In 2010, Los Angeles used enough water irrigating lawns to meet the needs of nearly a half-million average households for a year. That’s according to a new study by scientists at the University of Utah, who conducted what they say is the first city-scale assessment of water consumed by landscaping. Their findings show that Los Angeles’ landscaping consumed the equivalent of 100 gallons per person each day, with lawns accounting for 70 percent of that. Urban trees, it turns out, consume relatively little water. And by providing crucial shade, trees can actually make lawns less thirsty.