Groundwater is a major concern for the human community as it is the most important and reliable source of freshwater supply on earth. It is a renewable and finite natural resource, vital for man's life, socio-economic development and it is a valuable component of the ecosystem. However, groundwater is vulnerable to both natural and human impacts. An aquifer is an underground porous rock formation which allows water to move through it. Water wells are drilled through aquifers for easier access to groundwater in many areas and is sometimes the only access to fresh water. This book discusses the properties, roles, and provides further new research on aquifers.