It’s a hard figure to quantify, and estimates vary widely. For one, while indoor residential water use is relatively steady throughout the state, outdoor use — primarily for landscape irrigation
— varies dramatically, with homes in arid inland regions consuming significantly more water than those in coastal areas.
“There are large variations across the state,” notes Peter Bostrom from the California Department of Water Resources. “Outdoor use could be 25 percent [of a household's use] in Santa Cruz and 80 percent is Coachella … 15 percent of users account for 60 percent of overuse in landscape irrigation