What is a spring?
When the groundwater flows out at the ground surface, it is called a spring. In other words, the extrusion of the groundwater above the ground surface is known as the spring. The springs are formed at places where the water table intersects the ground surface. Due to the sudden inclination and dropdown in the level of the ground surface, the water table intersects the ground level because of its tendency to keep maintained at its particular level.
Types of Springs:
- Water Table Springs: The water table springs are found in depressions where the ground level is below the water table. When the water table meets the ground surface, the water of the elevated water table starts extruding out due to the gravitational pull.
- Artesian Spring: These springs come into being when the groundwater is under pressure, it finds its way to the land surface. When the pressure in the aquifer is greater than the atmospheric pressure, the spring flows out. This pressure is built because the aquifer is covered by a confining layer, which does not allow the water table to maintain its level. A spring is formed when the water reaches the surface through a fracture or porous layer. These types of springs usually occur along faults (a fracture in the earth), or in areas of great topographic relief such as cliffs or valleys.
- Contact Springs: When an impervious bed underlies a permeable bed, the groundwater is not allowed to percolate through the impervious bed, thus starts flowing out along the contact if the same is exposed by erosion.
- Seepage Spring: These springs are very common on sandy surfaces. They formed when groundwater slowly seeps out of the ground. Seepage springs usually occur in the sand, gravel, or organic materials and generally are found in depressions or valley bottoms. Seepage springs are different from artesian springs because they are not necessarily confined (contained below a dense layer of clay or other material) and usually have low flows.
- Perennial Springs: These springs are formed by draining a large surface area to lower down the surface as compared to the water table. The lowered ground surface allows the groundwater to exposed in the form of a spring.
- Karst Spring: They are also known as the Tubular Springs. Such type of springs is associated with limestone channels and caverns, and volcanic lava tubes. The caves or solution cavities in the limestone, or hollow “tubes” contain water. These caves and tubes range from may range from microscopic in size to large openings measuring many tens of feet across. Large tubular springs in some parts of the United States flow over a million gallons per minute. The large springs of southeastern Minnesota are tubular springs. Erosion may expose a cavernous rock, such as limestone containing groundwater. The springs formed in this way are called karst springs.
- Fault Spring: The flowing groundwater is checked along the fault planes and it may emerge out at lowering ground surface, thus forming a fault spring.
- Mineral Springs: Spring water may contain some dissolved mineral matter in sufficient concentration as to produce some taste or smell. Such springs are called mineral springs.
- Thermal Springs: The springs which discharge heated water are called thermal springs. These springs are also called ”geysers” or hot water springs.
- Intermittent Springs: Unlike perpetual springs they flow only during certain times of the year when rainfall or snowmelt is sufficient to recharge the soil and groundwater. But as the rainfall and snowmelt decreases, the spring flow gets reduced and finally stopped.