A group of scientists are flying over mountains in California and Colorado this spring, measuring snowpack with high-tech gadgets. NASA’s Airborne Snow Observatory mission started last month over the Sierra Nevadas and Southwestern Colorado’s Uncompahgre River Basin. The idea is to measure the snow in a way that’s never been done before, to get an idea of how much water is stored there. Snowpack accounts for 75 % of the Western United States’ freshwater supply. And, as demands for water grow, scientists are working on solutions.