Spring (hydrology)

Springs have long been important for humans as a source of fresh water, especially in arid regions which have relatively little annual rainfall.The action of the groundwater continually dissolves permeable bedrock such as limestone and dolomite, creating vast cave systems.Water may leak into the underground system from many sources including permeable earth, sinkholes, and losing streams.Human activity may also affect a spring's discharge—withdrawal of groundwater reduces the water pressure in an aquifer, decreasing the volume of flow.Groundwater tends to maintain a relatively long-term average temperature of its aquifer; so flow from a spring may be cooler than other sources on a summer day, but remain unfrozen in the winter.[23] Indigenous people of the American Southwest built spring-fed acequias that directed water to fields through canals.[24][25] A sacred spring, or holy well, is a small body of water emerging from underground and revered in some religious context: Christian and/or pagan and/or other.[26][27] The lore and mythology of ancient Greece was replete with sacred and storied springs—notably, the Corycian, Pierian and Castalian springs.The term "holy well" is commonly employed to refer to any water source of limited size (i.e., not a lake or river, but including pools and natural springs and seeps), which has some significance in local folklore.This can take the form of a particular name, an associated legend, the attribution of healing qualities to the water through the numinous presence of its guardian spirit or of a Christian saint, or a ceremony or ritual centered on the well site.[citation needed] The geothermally heated groundwater that flows from thermal springs is greater than human body temperature, usually in the range of 45–50 °C (113–122 °F), but they can be hotter.Because of the folklore surrounding hot springs and their claimed medical value, some have become tourist destinations and locations of physical rehabilitation centers.Narcissus gazed into "an unmuddied spring, silvery from its glittering waters, which neither shepherds nor she-goats grazing on the mountain nor any other cattle had touched, which neither bird nor beast nor branch fallen from a tree had disturbed."