Groundwater Information

Groundwater Concept Map

The basic idea of groundwater is depicted in the concept map above. First, moisture falls from the sky as some sort of precipitation. This can be rain, snow, sleet, or hail. Most of the precipitation that falls is considered runoff as it fails to soak into the soil. Instead it acts like water in a shower--the water runs down the walls and shower curtain and heads toward the drain. In nature's case, the water runs down slope and heads toward bodies of water like rivers and lakes. When precipitation runs off, it stays on the ground surface.

The water that does soak into the ground does so through a process called infiltration. The upper layers of the ground are slightly moist in comparison to the soil you can scuff with your toe. This upper layer is sort of like a slightly damp sponge. This layer is known as the Zone of Aeration. Notice that the word, Aeration, starts with the word--air. That's because there are air spaces between mineral grains and a watery film on the outside of the pores.

Beneath the Zone of Aeration is a zone known as the Capillary Fringe. This zone draws water up--like when you suck a drink with a straw--from the water-filled zones below. Below the Capillary Fringe is a thin zone known as the Water Table. The Water Table is the uppermost boundary to the Zone of Saturation. Despite what you may think, the Water Table isn't flat. It actually mimics the slope of the land above it; hence, it flows downward. The Zone of Saturation is like having a body of water below the ground. If you look at the figure above, you'll notice that there are no air spaces between the mineral grains. Instead, those spaces are full of water. In this zone, the sponge would be so wet that it drips. It can't hold anymore water.