What is a water-bearing geological formation used as a water source called?

An aquifer is defined as a geological formation that can store or transmit water, making it a crucial source of groundwater. Aquifers consist of permeable rock or sediment that allows water to flow through it. They are typically replenished by rainwater or surface water that seeps down through the soil and rock layers. This characteristic makes aquifers vital for supplying water for various uses, such as drinking, irrigation, and industrial processes.

Reservoirs, while also related to water sources, are artificial or natural lakes created to store large volumes of water, typically for human use, flood control, or ecological purposes, but they do not refer to the groundwater sources themselves. A borehole is a narrow shaft drilled into the ground to access groundwater, whereas a well is a structure created to extract water from an aquifer. While both boreholes and wells can draw water from an aquifer, they do not constitute the aquifer itself, which is the foundational water-bearing formation. Thus, recognizing the distinction, aquifers are specifically designated as the geological formations that store and supply groundwater.