Confined and Unconfined Aquifers

Have you ever been confined within your room after being grounded? Or perhaps you have been at a crowded party and just could not make your way to the food table because you were confined by the crowd of people.

Water in an aquifer can likewise be confined. Take a look at the diagram and see if you can tell why water might be confined within an aquifer.

Note the confined aquifer in the bottom part of the diagram. Why is it confined?
 

It cannot move upward past the dark blue layer. The dark blue layer must be made of something that does not allow water to easily move through it.

The diagram shows two types of aquifers: confined and unconfined. A confined aquifer is bounded by a layer of solid rock or very thick clay that does not easily let water through. It is impermeable. In contrast, an unconfined aquifer is not bounded on top by any impermeable layer. We can access water in both types of aquifers, but to get the water from a confined aquifer, we have to drill through the impermeable layer, which can sometimes be difficult, especially if it is a layer of very hard rock.