G5 The Water Cycle & Earth’s Spheres – 03

Once on the ground, water’s journey continues. Some of the water that falls to the ground may run across the surface. This process if called runoff as the liquid water travels to a river, lake, or ocean. Runoff may pick up fertilizer and other pollutants as it moves across Earth’s surface. In this way, runoff may pollute bodies of water. Water can also seep into the ground. This process is called infiltration. Some of the water may seep deep underground. In the field of Earth Science, the geosphere refers to the parts of our planet that are solid, such as Earth’s crust. Some may stay in the soil, part of the biosphere. Here, plants can absorb it with their roots. Underground water is a common source of drinking water.

The image below lets you see the water cycle. In the image it looks like the water cycle occurs mostly over land. That is far from the reality. In fact, most of the water that is recycled never reaches land. Why do you think this is? Here’s a hint, think back to how much of the earth is covered by water. Oceans cover about 2/3rds of the Earth’s surface. As a result, most evaporation comes from oceans. Most precipitation falls back into the ocean.


The water cycle is an endless cycle between Earth’s spheres. It has no beginning or end. Most of the water you drink may be billions of years old. You now know, it’s okay to drink. The water has been through a recycling process. That’s good news when you think about where this water has been. The water you are drinking may be very old. It may have even quenched the thirst of a dinosaur.