Aquifer

Aquifer can be defined as an underground layer of water-bearing formation. Aquifers act as reservoirs for groundwater. An aquifer fills with water from rain or melted snow that drains into the ground. In some areas, the water passes through the soil on top of the aquifer; in others, it enters through joints and cracks in rocks. The water moves downward until it meets less permeable rock.

Water from aquifers sometimes flows out in springs. Wells drilled into aquifers provide water for drinking, agriculture, and industrial uses.

There are different types of aquifers, according to the position of impermeable layer ‘(viz Confined aquifer, Unconfined aquifer, Semi confined aquifer and Perched aquifer)

Aquiclude

A body of relatively impermeable rock that is capable of absorbing water slowly but does not transmit it rapidly enough to supply a well or spring.

Aquitard

An aquitard is any geological formation of a rather semipervious nature that transmits water at slower rates than an aquifer. Freeze and Cherry (1979) describe an aquitard as the less-permeable beds in a stratigraphic sequence.

Perched aquifer

A perched aquifer is separated from another water-bearing stratum by an impermeable layer. Since this type of aquifer occurs above the regional (original) water table, in the unsaturated zone, the aquifer is called a perched aquifer. One main difference between perched and unconfined aquifers is their size (a perched aquifer is smaller).

In fact, a perched aquifer is a very small, unconfined aquifer that doesn’t contain much water and is only recharged by local precipitation. A well drilled into a perched aquifer usually yields only enough water for a single household.