Spring (hydrosphere)
A spring is a component of the hydrosphere, namely any natural
occurrence where water flows to the surface of the earth from below
the surface. Thus it is 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 (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.
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 such as a hot
spring.
The action of the groundwater continually dissolves permeable
bedrock such as limestone and dolomite creating vast cave
systems.
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
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 meaning they discharge at least 100 cubic feet of water
per second (cfs), or about 64.6 million gallons per day
(mgd).
The scale for spring flow is as follows:
- 0 Magnitude - no flow (sites of past/historic flow)
- 1st Magnitude - > 100 cubic feet per second (cfs)
- 2nd Magnitude - 10 -100 cfs
- 3rd Magnitude - 1 - 10 cfs
- 4th Magnitude - 100 gal/min (gallons per minute) - 1 cfs (448
gal/min)
- 5th Magnitude - 10 to 100 gal/min
- 6th Magnitude - 1 to 10 gal/min
- 7th Magnitude - 1 pint to 1 gal/min
- 8th Magnitude - Less than 1 pint/min
In order to log this cache, email me the
following.
1. From reading the description above, what type of spring is
Grotto Spring?
2. Using the scale above, what is the magnitude of Grotto
Spring?