An unconfined aquifer is a groundwater reservoir that is directly open to the atmosphere through porous material, such as soil or permeable rock, allowing for the free movement of water. Unconfined aquifers are significant in hydrogeology for understanding groundwater recharge, water table dynamics, and the availability of water resources.
Reference: Freeze, R. A., & Cherry, J. A. (1979). “Groundwater.” Prentice Hall.