Most of the water we see each day is in ponds, rivers, oceans, streams, lakes, puddles, and other places on top of the ground. What we don’t often see is the water that soaks into the ground. We use a special word to describe water that has gone underground: groundwater.

If you were to travel underground, you would eventually get deep enough to find all the rock around you soaked with water—You’d have entered the saturated zone! The water in the saturated zone is called an aquifer. The height of water in the saturated zone is called the water table. In dry places, the water table is very deep, but in moist places, the water table is very shallow. When the water table is higher than the surface of the ground, there are streams, rivers, and lakes on the land.