At the southern end of California, residents have been assured their water supplies are secure and plentiful despite the state’s severe drought.

In Marin County, 500 miles north, lawn sprinklers are allowed only two days a week, washing a car at home is banned, and decorative fountains can’t be refilled. The orders are part of an effort by the local water district to cut usage by 40% after a precipitous fall in the local reservoirs.

The pain of a two-year drought drying up the American West isn’t being felt evenly across the country’s most populous state.

That is because Southern California water agencies have for decades invested in new ways to diversify their supplies and recycle what they get, say people who study and work with water in the West. In Northern California, meanwhile, a history of more plentiful rain and snow meant many communities were less prepared for the latest drought and now more homes and businesses must cut back.