Earth has about 370,000,000,000,000,000,000 (quintillion) gallons of water, with some sources easier to access and use than others. The water budget tells us where that water is – key information that helps better plan for the future. SWOT, launching Dec. 15, will survey nearly all water on Earth’s surface for the first time. It will measure the height of the world’s ocean, rivers, and lakes, helping scientists track how fresh and saltwater bodies change over time. 🌊 Here are 5 things to know: