The Water Cycle: Following the Water
Precipitation falls on the ground, but what happens to that water depends on the geography of the land at any particular place.
The movement of water through the Earth's many layers is evaluated using ground and satellite measurements and computer models.
Explore how water moves across land and returns to the ocean in the final installment of the water cycle series.
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.
Groundwater gains and losses vary dramatically on our planet as a result of precipitation levels and the effects of evaporation due to sunlight.
The amount of precipitation retained by the very top layer of soils on Earth is seen in this snapshot of soil wetness on each continent.
Water on land is diverted into rivers or stored underground in aquifers (multi-colored areas) for consumption by plants, animals and humans.