Demonstration of How Aquifers and Aquitards

This demonstration shows how aquifers and aquitards work.
http://en.wikipedia.org/wiki/Aquifer

The container on the left contains sand,
The container on the right contains clay,
The container in the central has a layer of clay between two layers of sand

Water moves quickly through sand and slowly through clay. The clay layer in the central container acts like an aquitard, slowing the rate of water movement down. Water is captured in the sandy layer above the aquitard, much like water is stored in an unconfined aquifer.