On an average day nearly 300 million gallons of water issue from
Big Spring in
Missouri at a rate of 465 cfs.
A
spring is any natural occurrence where water flows on to the surface of the earth from below the surface, and is thus where the
aquifer surface meets the ground surface.
Formation
A spring may be the result of
karst topography where surface water has infiltrated the Earth's surface (recharge area), becoming part of the area
groundwater. The groundwater then travels though a network of cracks and fissures - openings ranging from intergranular spaces to large
caves. The water eventually emerges from below the surface, in the form of a spring.
The forcing of the spring to the surface can be the result of a confined
aquifer in which the recharge area of the spring water table rests at a higher elevation than that of the outlet. Spring water forced to the surface by elevated sources are
artesian wells. This is possible even if the outlet is in the form of a 300-foot deep cave. In this case the cave is used like a hose by the higher elevated recharge area of groundwater to exit through the lower elevation opening.
Nonartesian springs may simply flow from a higher elevation through the earth to a lower elevation and exit in the form of a spring, using the ground like a drainage pipe.
Still other springs are the result of pressure from an underground source in the earth, in the form of
volcanic activity. The result can be water at elevated temperature as a
hot spring.
The action of the groundwater continually dissolves permeable bedrock such as
limestone and
dolmite creating vast cave systems
[http://ga.water.usgs.gov/edu/watercyclesprings.html].
Types of spring outlets
- Seepage or filtration spring. The term seep refers to springs with small flow rates in which the source water has filtered into permeable earth.
- Fracture springs, discharge from faults, joints, or fissures in the earth, in which springs have followed a natural course of voids or weaknesses in the bedrock.
- Tubular springs are essentially water dissolved and create underground channels, basically cave systems.
Spring flow
thumb|right|vertical|The stream flowing into this cave at the bottom of Grand Gulf, a huge sinkhole in Missouri, resurfaces at Mammoth Spring in Arkansas.
Spring discharge, or resurgence, is determined by the "spring's" recharge basin. Factors include the size of the area in which groundwater is captured, the amount of precipitation, the size of capture points, and the size of the spring outlet. Water may leak into the underground system from many sources including permeable earth, sinkholes, and
losing streams. In some cases entire
creeks seemingly disappear as the water sinks into the ground via the stream bed.
Grand Gulf State Park in
Missouri is an example of an entire creek vanishing into the groundwater system. The water emerges nine miles away, forming some of the discharge of
Mammoth Spring in
Arkansas.
Classification
Springs are often classified by the volume of the water they discharge. The largest springs are called "first-magnitude," defined as springs that discharge water at a rate of at least 2800 liters or of water per second. Some locations contain many first-magnitude springs, such as
Central Florida where there are 33
[http://www.tfn.net/springs/Springbook/FirstMagnitude.htm] known to be that size, the southern
Missouri Ozarks (11 known of first-magnitude), and 11
[http://www.if.uidaho.edu/~johnson/ifiwrri/1000spgs.html] more in the
Thousand Springs area along the
Snake River in
Idaho. The scale for spring flow is as follows:
Fontaine de Vaucluse or Spring of Vaucluse in
France discharges about 470 million gallons (1.8
billion liters) of water per day at a rate of 727 cubic feet (21 m
3) per second.
Spring water content
Minerals become dissolved in the water as it moves through the underground
rocks. This may give the water flavor and even
carbon dioxide bubbles, depending on the nature of the
geology through which it passes. This is why spring water is often bottled and sold as
mineral water, although the term is often the subject of
deceptive advertising. Springs that contain significant amounts of minerals are sometimes called '
mineral springs'. Springs that contain large amounts of dissolved
sodium salts, mostly
sodium carbonate, are called 'soda springs'. Many resorts have developed around mineral springs and are known as
spa towns.
A
stream carrying the outflow of a spring to a nearby primary stream is called a spring branch or run. Groundwater tends to maintain a relatively long-term average temperature of its aquifer; so flow from a spring may be cooler than a summer day, but remain unfrozen in the winter. The cool
water of a spring and its branch may harbor species such as certain
trout that are otherwise ill-suited to a warmer local
climate.
Historic uses
Springs have been used for a variety of human needs including drinking water, powering of
mills, and navigation, and more recently some have been used for electricity generation.
Modern uses
Present-day uses include recreational activities, such as trout-fishing, swimming, and floating. The water is also used for livestock and fish hatcheries.
Notable springs
See also
