To better measure the water in our snow, California is sending sharper eyes up into the sky. Two sensors peer out from a turboprop aircraft, soaring from Mammoth Yosemite Airport over the white Sierra Nevada – collecting data that tells us almost exactly how much water we’ll have this summer. Last week’s findings: 1.1 million acre-feet, or 350 billion gallons of water in the mountain snow of Yosemite’s Tuolumne River basin, which flows into Hetch Hetchy Reservoir and provides water to major Central Valley irrigation districts, San Francisco and several other Bay Area communities.