A spring is a point where water flows out of the ground. A spring may flow the whole year or only sometimes. This depends on the water getting into the ground all of the time (rain) or only once in a while (snow melting).
A spring often sends water down, along the land. This is how rivers start.
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 through 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 karst 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 (91 m) 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.
Non-artesian 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.
The action of the groundwater continually dissolves permeable bedrock such as limestone and dolomite, creating vast cave systems.
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Spring (water) Facts for Kids. Kiddle Encyclopedia.