Freshwater seems abundant, but when accounting for all the water on Earth, it's in limited supply. Just three percent of the water on our planet is freshwater. A majority of this water, about two percent of the world total, is contained in glaciers and ice sheets or stored below ground. The remaining one percent is found in lakes, rivers and wetland areas or transported through the atmosphere in the form of water vapor, clouds and precipitation. Rain and snowfall replenish freshwater sources, making it vital to know when, where and how much water is falling at any given time. Using NASA's Global Precipitation Measurement satellite, researchers can track precipitation worldwide and monitor levels from space.

For more information on Earth's water resources, visit: http://water.usgs.gov/edu/earthwherewater.html