What defines a groundwater aquifer?

A groundwater aquifer is specifically defined as a geological formation that can not only store water but also transmit it efficiently through the spaces between the particles or fractures in the rock or sediment. This dual capacity is crucial for the aquifer's role in supplying water to wells and springs, making it an essential component of the hydrological cycle.

The ability to store water means that the aquifer has the necessary porosity, which refers to the volume of the voids or spaces within the rock or sediment where water can be held. Meanwhile, the capacity to transmit water is a function of the permeability of the material, which dictates how easily water can flow through it.

This definition highlights the importance of both storing and transmitting capabilities in distinguishing aquifers from other geological formations. For example, a formation that stores oil does not necessarily have the characteristics needed to store or transmit water effectively. Man-made structures for water conservation, such as reservoirs or cisterns, are not natural geological formations and do not meet the criteria for being termed an aquifer. Similarly, high mineral content in a location does not define it as an aquifer, as this characteristic can apply to various geological formations without implying they can store or transmit water.