Aquifer - From Wikipedia, the free encyclopedia - An aquifer is an underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, silt, or clay) from which groundwater can be usefully extracted using water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. Related terms include: an aquitard, which is an impermeable layer along an aquifer, and an aquiclude (or aquifuge), which is a solid, impermeable area beneath an aquifer. The surface of saturated material in an aquifer is known as the water table.

An aquifer is any soil and/or rock formation that contains enough groundwater to be used for drinking water, industry or agriculture. Large underground amounts of clay or silt mixed with stones result in low yield aquifers of less than 10 gallons a minute. (Half a gallon per minute provides 700 gallons a day.) These recharge from local rainfall. Different rock structures the contain water in their fractures, fissures, and cracks are termed variable yield aquifers. Yields from these wells can vary from less than 1 gallon per minute to 500 gallons per minute, and they recharge from a large area. In New York State, the highest yields of water come from aquifers formed by sand and gravel during glaciation. (Valleys where glacial meltwater streams flowed usually contain extensive sand and gravel deposits.) Sometimes these high yield aquifers can reach thousands of gallons per minute. Source

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Underground sources of water

 a body of permeable rock that is capable of storing significant quantities of water, that is underlain by impermeable material, and through which groundwater moves.Source 

 A geological formation usually composed of sand, gravel, or permeable rock that is capable of storing and yielding significant amounts of water. Source 

 Aquifer Source of Pure Water - To tap the groundwater in an aquifer, wells are dug until they reach the top layer of the aquifer, the water table. The water table is not flat as its name makes it seem. It has peaks and valleys that echo the shape of the land above it. When a lot of water is pumped from an aquifer, or when there is a dry spell, the water table sinks lower.

 South Dakota Aquifers - An aquifer is any rock or sediment with spaces that hold water, and through which significant quantities of water move. The water contained in these underground spaces is called ground water. Although ground water can flow freely through large underground spaces, more often it seeps slowly through the intricate small pores of rock or sediment. Examples of aquifer s include: sand and gravel layers (i.e., buried river systems and flood plains); fracture systems in brittle rocks (i.e., granite or quartzite); and fracture systems or solution cavities in easily dissolved rocks, such as limestone.