Water Table Aquifer Diagram — free printable diagram

What a water table and aquifer diagram shows

Not all the rain that falls runs into rivers; much of it soaks into the ground and is stored in the pores and cracks of the rock beneath. A rock that both holds and transmits that water is an aquifer, and the water table is the top surface of the saturated zone within it — the level below which every space in the rock is full of water. The diagram is drawn as a cross-section because both ideas are about depth.

Groundwater

Water held underground in soil and rock

Aquifer

A rock that stores groundwater and lets it flow through

Water table

The top surface of the fully saturated zone

Permeable rock

Lets water pass through — sandstone, chalk, limestone

Impermeable rock

Does not let water through — clay, granite

Recharge

Rainwater infiltrating from the surface

Well or borehole

Sunk below the water table to reach the water

Spring

Where the water table meets the ground surface

• The water table is a definition about saturation, not a buried lake. Above it the pores in the rock hold both air and water; below it they are completely full, and that boundary is the line the diagram labels.
• An aquifer needs two things: permeable rock with spaces to hold water, and usually an impermeable layer beneath to stop it draining away.
• The water table is not flat. It broadly follows the shape of the land above it, and it rises in wet weather and falls in dry spells and through the summer.
• That is why a well has to reach below the lowest level the water table ever falls to. A well sunk only just below the winter level runs dry in summer.
• A spring appears where the water table intersects the surface — commonly on a hillside at the junction between a permeable rock and an impermeable one beneath it.
• Aquifers supply drinking water in many parts of the world. Taking water out faster than rainfall recharges it lowers the water table, which is why over-abstraction is studied alongside the diagram.