In California, news of a historically powerful El Niño oceanic warming event is stoking hopes that winter rains will ease the state’s brutal drought . But for farmers in the Central Valley, one of the globe’s most productive agricultural regions, water troubles go much deeper—literally—than the current lack of precipitation. That’s the message of an eye-popping report from researchers at the US Geological Survey. This chart tells the story: To understand it, note that in the arid Central Valley, farmers get water to irrigate their crops in two ways. The first is through massive, government-built projects that deliver melted snow from the Sierra Nevada mountains. The second is by digging wells into the ground and pumping water […]