A natural resurgence of groundwater, usually along a hillside or from a valley floor.
Natural flow of water from the ground or from rocks, representing an outlet for the water that has accumulated in permeable rock strata underground.
perennial spring A spring that flows continuously.
intermittent spring a spring alternately containing and empty of water.
periodic spring a spring having or marked by repeated cycles.
Adjective used to designate an intake or resurgence operating only during rainy seasons; in some areas reversible; equivalent to intermittent
emergence. Point at which an underground stream comes to the surface. See also exsurgence; resurgence; rise.
exsurgence. Point at which an underground stream reaches the surface if stream has no known surface headwaters. See also emergence; resurgence.
resurgence. Point at which an underground stream reaches the surface and becomes a surface stream. In European literature, the term is reserved for the reemergence of a stream that has earlier sunk upstream. The term exsurgence is applied to a stream without known surface headwaters.
Watson Hiner Monroe (1970): A Glossary of Karst Terminology, Geological Survey Water-supply Paper 1899-k, Library of Congress catalog-card No. 75-607530 DOI online
Springs in karst areas differ from normal springs: they normally have a much higher production, as they are just the end of a waterfilled cave system. Also they are highly dependent on the weather. Every rain and, of course, the snow melting leads to increased production. And finally, the water is often quite shortly underground, and when it reappears it is not sufficiently cleaned by filter materials or bacteria.
Karst springs regularly fall dry in dry periods, eg during the summer, such springs are called Seasonal Spring. On the other hand, the water quality is often poor! Both effects have the same reason: the water flows rather fast through cave systems, there is not enough time for micro organisms to clean the water. So karst springs are not a good source for water supply.
A famous accident happend about 100 years ago in the karst area Jura, France. There is the location of the still existing and famous Pernod Company. One day there was a fire in the plant and many hectolitres of Absinth accidentialy oozed away. Already one day later the water of the Loue Spring got milky and the air smelled like anis and alcohol.