- An aquifer is a geological formation made up of enough permeable material which allows storage of water and at the same time it will allow movement of water through it under ordinary condition.e.g., Sand, Gravels
- An aquiclude may be defined as a geological formation of relatively impermeable material which permits storage of water but it is not capable of transmitting water through it. e.g., clay
- Aquitard is a geological formation of poor permeability, but through which seepage is possible and hence it won’t yield water freely to wells. It may transmit vertically appreciable quantities of water to or from adjacent aquifers. Sandy clay is an example of aquitard.
- An aquifuge may be defined as a geological formation of impermeable material which neither contains nor transmits water through it.For example :Solid rocks.
Types of aquifer
It is one, in which water is not under any pressure or say water table surface coincides with the upper surface zone of saturation.
Unconfined aquifer is also known as water table aquifer, phreatic aquifer or non-artesian aquifer.
A confined aquifer is one in which water table is under pressure greater than atmospheric pressure due to overlying impermeable strata. It is also known as artesian or pressure aquifer.