In a scene in the movie Chinatown, a pro-water-bond politician harangues the voters: “Los Angeles is a desert community. Beneath this building, beneath our streets, is a desert. And without water the dust will rise up and cover us as though we never existed!” But L.A. isn’t a desert. West of the mountains it is a semiarid Mediterranean climate, with high peaks that capture winter rain and snow that flow through three major river systems and fill subterranean aquifers—natural layers of porous sand and rock that can hold prodigious amounts of water. The L.A. region has abundant aquifers, getting 40 to 45 percent of its water from the ground. Some cities, such as San Bernardino, rely 100 percent on groundwater, while others, like Pasadena (36 percent) and Orange County (60 percent) mix it with imported water. The temptation to pump out more water than nature puts in every year is too strong for many water districts to resist. Most of the state’s 450 or so aquifers are overdrawn, like a bank account, with bad results leading to ground subsidence, dried-up springs, and falling water tables.
We could actually have more groundwater, but we’ve paved so much of the landscape that less rainwater can percolate into the aquifers before running off into sewers or into the ocean. We’ve also contaminated aquifers into disuse. Santa Monica once got 70 percent of its water from wells—until the gasoline additive MTBE leaked from underground storage tanks. Perchlorate rocket fuel has contaminated other wells. Ambitious—and expensive—efforts are under way to clean up polluted wells (the cost in the Valley alone could be $1 billion). There are even plans to capture more rainfall so it can soak into the ground and into aquifers rather than traveling into the sea, the way it currently does through storm drains.