On par with mission architecture or cattle ranching is another consequential relic of Spanish colonialism in California: the idea that water pumped from underground belongs to whoever owns the land above.

In the Central Valley, a major danger of unregulated pumping has been a drooping of the surface at a rate of one foot a year. Here, in the Salinas Valley, so much freshwater has been extracted that, in some aquifers, the natural flow from continent to ocean has reversed – seawater is pushing through gravel and sand into groundwater sources, threatening to spoil a critical household and agricultural supply.