Which term refers to underground, water-bearing formations yielding useful quantities of water?

The term that refers to underground, water-bearing formations that yield useful quantities of water is aquifers. Aquifers are geological formations, usually composed of layers of permeable rock or sediment, that can store and transmit groundwater, making them essential sources of freshwater for various uses, including drinking water, irrigation, and industrial processes. The characteristics of aquifers, such as their porosity and permeability, determine how much water they can hold and how easily it can be extracted.

In contrast, reservoirs are surface water bodies created by damming rivers or streams, storing water for various uses, but they are not underground formations. Watersheds refer to the land area that drains into a particular body of water, such as a river or lake, influencing the water quality and quantity that flow into that system, and springs are locations where groundwater naturally flows to the surface, usually not representing large underground formations themselves. Understanding these terms helps in recognizing the significant role aquifers play in the water supply system.