In hydrology, a spring is a water body that is formed as a result of water flowing to the Earth’s surface from an aquifer.
Formation of a Spring
A spring can be formed due to karst topography, which occurs when soluble rocks like dolomite, limestone, and gypsum dissolve. Beneath the hollows created, water finds its way up to the surface of the Earth. The hollows do not necessarily have to be straight, but can be caves, sinkholes, fissures or a network of cracks. This type of spring is known as a karst spring.
On the other hand, an underground aquifer on an elevated water table can force water out through the Earth’s surface when it is low-lying. Water from confined aquifers is forced out through a cave to make artesian wells. Non-artesian wells can also be formed in similar ways, and other springs are formed due to pressure from an underground water source. This type of spring is usually caused by volcanic activity, and is a hot spring.
Types of Springs
There are different types of springs that vary based on the formation process. For instance, Tubular springs occur when water flows from an underground cavern. Fracture springs are caused by natural paths in the Earth, including voids and weaknesses in bedrock. These follow joints and come out as discharge from faults. Finally, seepage spring, also known as filtration springs, occur when water flows slowly but gradually through small holes or porous material.
Classification of Springs
Springs are typically classified according to the amount of water they discharge. There are a total of 8 magnitudes of springs. First magnitude springs discharge at least 2,800 liters of water per second and are the largest, while the smallest springs discharge a maximum of 1 pint per second. There are also springs that no longer exist or have become inactive, perhaps due to the closure of the channel connecting the source to the Earth's surface.
Uses of Springs
Like any source of water, springs are used for various reasons. Springs can be used as a source of water for domestic use, electricity generation, fish hatcheries, irrigation, swimming, recreational activities, and navigation. Some springs have also been used commercially as a means of producing bottled mineral water.
In some religious contexts, springs have been considered sacred by Pagans, Christians, and other religions. For example, sacred springs like Pierian, Corycian, and Castalian were common in Ancient Greek mythology.
Some notable springs around the world include Baotu Spring (China), Gihon Spring (Jerusalem), Aachtopf (Germany), Blue Spring (Missouri, USA), Niagara Springs (Idaho, USA), and Silver Springs (Florida, USA).