|
- An aquifer is any soil or rock formation that supplies an acceptable quantity and quality of groundwater.
- The saturated zone can have two types of productive aquifers within it.
- An unconfined aquifer is directly beneath the unsaturated zone with no barriers in between. The water table is the top surface of an unconfined aquifer. Unconfined aquifers have a bottom barrier zone that slows the water movement and allows it to build up in the unsaturated zone.
- A confined aquifer has a barrier both above and below. These barriers are called confining layers. Confining layers are made up of geologic materials that greatly slow or restrict the movement of groundwater (such as clay).
- The saturated zone can have more than one confined aquifer in it, but only one unconfined aquifer.
- In areas where a small confining layer is present, there may be perched groundwater in the unconfined aquifer. Since the volume of water held in these areas is minimal, they are generally not used as a source of drinking water.
- Water pressure within a confined aquifer is higher than in an unconfined aquifer because of the weight of the overlying formations coupled with their confined nature (because the water cannot escape easily through the confining layers, pressure builds up).
 
|
