The varied landscapes of the United States have unique relationships with water. On the East Coast, rain is a regular occurrence. In the West, drought is a constant threat. Rivers and lakes fed by rainfall, snowmelt or a mix of both provide two-thirds of the country's drinking water while also supporting agriculture. Managing these water resources requires balancing growing demand for water in the face of shifting availability and changing climate. Many state and federal agencies and other organizations turn to NASA research, satellite data and analytical tools to help tackle these issues. Since the 1960s, NASA has been steadily expanding its view of how fresh water moves around the planet. Early satellites that imaged clouds and snow cover evolved to more recent missions that quantify rain and snowfall worldwide every half-hour, make daily observations of global snow cover, detect changes in aquifers deep underground, and monitor moisture in soils every few days. These observations are some of the most powerful assets scientists have when studying the water cycle, how it affects people and their water supplies, and how it may change in a warming climate. At NASA, researchers maintain and refine these data sets, providing them to the public at no cost. NASA researchers also help to interpret the information with sophisticated computer programs that integrate the disparate data sets and fill gaps to create a coherent picture of where and how water moves around the planet every day.