The Water Cycle: Following The Water

One hundred and three trillion tons of rain and snow fall on land each year. A lot of that water, almost 66 trillion tons, goes right back into the air as water vapor from evaporation or plant transpiration. The remaining 37 trillion tons eventually returns to the oceans, restoring water that had evaporated, completing the water cycle. However, the path water takes before it reaches the oceans is complex. The land surface is very diverse, and characteristics such as soil type, slope and altitude affect how water moves. Does the water stay around long enough for plants or animals to consume? Is there enough water upstream of a community to maintain its water supply? How much water filters down to underground aquifers? Scientists study these questions because water plays such a vital role in our lives. The visualizations below illustrate on a globe and map the movement of water on land—from accumulation and storage of precipitation in soil layers, to its transport via interconnected systems of rivers throughout the planet.