Springs

springs A spring is a location where groundwater flows naturally, that is, discharges to the land surface or into a surface of water body such as a stream, a lake, or even the sea. The source of this discharge may be a water-table aquifer in which the water-table intersects the land surface. Springs associated with water-table aquifers are usually found in valleys or lowlands, where they provide water to wetlands and base flow to streams. Springs can occur in uplands if zones of perched water extend laterally to cliff faces or other steep slopes. Springs are also found in places where a confined aquifer is connected to the land surface by a permeable fracture or fault zone. If the confined aquifer is at great depth, where temperatures are naturally elevated, or is connected to heat sources associated with recent volcanic activity, the springs can discharge hot water, often of high salinity. Spring water is often assumed to be unusually pure and healthful. Although spring water from confined aquifers may be less susceptible to shallow sources of contamination than surface water, the fact that water comes from a spring is no guarantee of high quality.

J. Bahr

spring in geology, natural flow of water from the ground or from rocks, representing an outlet for the water that has accumulated in permeable rock strata underground. Some of the water that falls as rain soaks into the soil and is drawn downward by gravity to a depth where all openings and pore spaces in the rock or soil have become completely saturated with water. This region is called the zone of saturation, and the water it holds, groundwater. The upper surface of the zone of saturation is called the water table. Above the water table lies the zone of aeration, where the pore spaces in the soil are quite dry and are filled with air. When the upper surface of the groundwater (water table) intersects a sloping land surface, a spring appears. The occurrence of springs is closely related to the geology of an area. If an impervious layer of rock, such as a clay deposit, underlies a layer of saturated soil or rock, then a line of springs will tend to appear on a slope where the clay layer outcrops. Igneous rocks are also impervious to water, yet they are often extensively fractured, and springs commonly appear where these fractures come to the surface. Fractures in limestone are often enlarged by the dissolving action of groundwater, forming small underground channels and caves. Where these channels outcrop, springs are likely to be found. Springs are common along major faults because groundwater reaches the surface along the fault plane. Lines of springs help locate the position of faults such as the San Andreas of California. Springs can be a valuable water resource, and improvement in flow can often be accomplished simply by driving a pipe into the ground at the point where water seeps from the ground. Sometimes it is advisable to divert the spring water into a cistern or other storage reservoir from which the water can be pumped at will. When the water, because of the geological structure of the strata, issues under pressure, the spring is called artesian (see artesian well ). Another type of spring is the geyser . Hot springs occur when the water issues from great depths or is heated by near-surface hot volcanic rock, as in Yellowstone National Park, Iceland, and New Zealand. Mineral springs are those with a high mineral content, usually silica or lime, dissolved from the rocks through which the water has passed (see mineral water ). Many ancient city-states, such as Troy, had their sites determined by springs. Pioneer farmhouses often were located in the same way.

spring A flow of water above ground level that occurs where the water-table intercepts the ground surface. Where the flow from a spring is not distinct (i.e. it does not give rise to obvious trickles) but tends to be somewhat dispersed, the flow is more correctly termed a ‘seep’. The reappearance of surface water that had been diverted underground in a karst region is a type of spring known as a ‘resurgence’. A major variety is the ‘Vauclusian spring’, named after the Fontaine de Vaucluse, southern France, and descriptive of the upward emergence of an underground river from a flooded solution channel.