How Weather Forecasts Can Help Dams Supply More Water

Between Christmas and January this year, a parade of nine atmospheric rivers — vast streams of water vapor flowing east from the tropical Pacific — pummeled California. The trillions of gallons of rain poured on the state caused widespread flooding. While the rain topped up some drought-depleted reservoirs and aquifers and filled out snowpack in the Sierra Nevada, much of the water quickly ran off into the sea, flowing off asphalt and farms or released from reservoirs to prevent further flooding.