Aquifer

An Aquifer is a geological formation containing, temporarily or permanently, available water, and made up of permeable rocks from which water can come naturally and/or by extraction.

There are:

- Unconfined aquifers: aquifers on a layer of very low permeability above which is a non-saturated zone.
- Confined aquifers: in a confined aquifer, the underground water is confined between two formations of very low permeability. When a confined aquifer is reached by drilling, the water rises to the surface in the well.