Unit 4: Hydrology

Overall, the study calculates that more than 15 billion tons of freshwater flow through invisible underground networks into the ocean along the contiguous U.S. coastline every year. That sounds like a lot of water, but it's less than 1 percent of the total amount that flows from the contiguous United States into the ocean, said study co-author Cedric David of JPL. The other 99 percent comes from rivers and surface runoff. NASA 8/2016