Why Water Use Varies So Widely Across California

But most of it can be chalked up to something Californians either love, or love to hate: our yards. “The biggest driver of the difference is outdoor water usage,” said Jay Lund, co-director of the Center for Watershed Sciences at the University of California, Davis.

Half of California’s annual water usage is considered environmental water, meaning it flows through protected rivers or supports wetlands in wildland preserves, according to the Public Policy Institute of California. The other 50 percent is for human use — 40 percent for agriculture and 10 percent for urban use, split between indoor (drinking water, showers) and outdoor (lawns, washing cars).

But the relatively warm, dry weather in California tips the scales toward outdoor consumption. Plants quickly evaporate water, so keeping them green here is more water-intensive than, say, on the East Coast, where it rains in the summer.

In dense, urban environments, people tend to have smaller yards, so there’s less green to water. And in cooler, coastal regions, water demands dip even further as there’s less evaporation. That’s how you end up with San Francisco’s low water consumption rate.

And in a place like Lassen County, in the northeastern part of the state, yards are much larger and lead to more irrigation, especially as the weather heats up. “It still gets very warm in the summer time, so if you keep your property green, you spend a lot of water,” Lund said.

So you can see why California so far has focused its drought restrictions so heavily on yards.

In January, state officials announced penalties for watering yards after a rainstorm. Starting this month, the Metropolitan Water District of Southern California, one of the largest water distributors in the nation, restricted outdoor watering to one day a week.