A spring is a place where groundwater emerges permanently or temporarily at the surface of the terrain in a natural way. In most cases, it is (meteoric) groundwater fed by precipitation. Only in rare cases does the water come from deeper parts of the earth's interior ( juvenile water ).
Sources can be classified according to several aspects: according to the hydrostatic pressure of the groundwater, according to the course of the spring discharge over time , according to the source temperature , according to the content of dissolved gaseous and solid substances, according to structural features or according to the type of habitats created by the discharge .
Classification according to hydrostatic pressure
- Outflow of free groundwater : The pressure at the groundwater outlet is the same as the atmospheric pressure; one also speaks of descending springs.
- Discharge of constrained groundwater ( artesian spring , spring spring ): The pressure at the groundwater outlet is greater than the atmospheric pressure; one also speaks of rising springs.
Classification according to the temporal course of the spring discharge
- Perennial springs flow continuously, and their discharge can fluctuate greatly.
- Intermittent springs dry out at times. Intermittent karst springs are also called hunger wells .
Classification according to source temperature
The water temperature of a spring usually corresponds to the local mean annual temperature of the air and is constant over the season. In Central Europe the temperature is then around 6 to 10 ° C, in tropical areas around 20 to 25 ° C. If the feeding aquifer is less than 20 meters deep, there may be slight seasonal fluctuations in the source temperature.
- Akratopegen: springs, the temperature of which corresponds to the mean local annual temperature .
- Acratotherms: springs whose water temperature is above the mean annual temperature of the air ( thermal springs ).
Classification according to the content of dissolved substances
Sources that have a particularly high content of dissolved gaseous or solid substances are called mineral springs . Balneology deals with the effects of healing springs . Mineral springs can be further subdivided into brine springs , sulfur springs, acidic springs, alkaline springs, bitter springs, iron springs and radioactive springs. The carrier of radioactivity in radioactive sources is the noble gas radon, which usually arises from the decay of uranium or thorium-containing minerals in granite or gneiss rocks (cf. radon balneology ).
Classification according to structural features in the source catchment area
- Karst springs : Carbonate rocks that occur frequently all over the world often have the property of dissolving when exposed to water containing CO 2 (usual precipitation). The then calcareous water emerges relatively quickly in cracks / crevices / crevices / passages / caves as a karst spring.
- Layer sources : groundwater moves over a damming layer of rock to the point of discharge.
- Overflow sources: also called overflow sources, groundwater accumulates over a rock layer down to the deepest possible outlet, especially in the case of laterally limiting (damming) rocks (e.g. at faults or in front of sintered limestone crusts ) also called damming sources .
- Constriction sources: special form of the overflow source; In the aquifer itself, hydrostatic pressure builds up in front of places of lower permeability, which can lead to the groundwater accumulation up to the surface of the earth and there to the (often only temporarily) spring discharge.
- Crevice sources: in rocks with crevice systems or cavities created by solution, the groundwater can move quickly and thus escape even with heavy pouring on the surface. Rivers running underground can also emerge in large karst springs. Also glacier gates can be classified here.
- Artesian springs : groundwater that is pressed under a rock layer that descends in the direction of flow and reaches the surface under pressure at a few permeable points (such as fault lines ).
- Spring springs : volcanically heated groundwater or groundwater mixed with carbon dioxide repeatedly forms fountains when it emerges, also known as geysers at high heights .
- Fold source: a source that is linked to a geological fold structure (special case of a stratified or overflow source ).
- Fault source: also known as a fault source, a source that occurs at a geological fault , especially if water-impermeable, damming and permeable rocks are offset on the fault surface. So it often comes to source horizons that follow the outcrop of the corresponding disturbance. Sources of interference can include special forms of overflow sources. If the rock along the fault is severely shattered by the movement and has a very high degree of permeability, the sources of the fault can also be artesian.
Classification according to structural features of the source location
- Rheokrene ( flowing or bubbling spring ) show a clearly recognizable, locally limited outlet with a visible drainage. It can flow in a laminar manner and even have stagnant water zones, or it can form a torrent or waterfall after emerging from crevices in steep terrain ( fall source , fall source ).
- Helokrene ( Sickerquelle , sump source ) are characterized by flat emerging groundwater, which collects in a sump from source smallest Quellrinnsalen. Such a source area can, depending on the climatic and geological situation, extend over square kilometers. In the lowlands, apart from a few rising springs, Helokrene usually has a low discharge.
- Limnokrene ( Tümpel source , funnel source , source pond , source pools ) are yielding a stagnant water forms source outlets at the base of a trough (a source pool, pond or even a source Quellsee). By overflowing the edge of the water a source stream is created. Such a spring pool can reach great depths in karst areas .
- Submarine springs occur particularly in karst areas.
- Endorheic sources have no drainage; their water seeps away again after a short stretch of flow.
- Contained sources are surrounded by an artificial source or they are designed like a monument.
( Wells are artificial groundwater outcrops and are not referred to as sources .)
Sources as living space
The so-called krenal , i.e. the spring habitat, is a small-scale habitat whose physical and chemical factors, with the exception of karst springs, remain fairly constant. If they change, it can have a major impact on the krenal. Except in the case of heavy pollution of the groundwater, sources are oligotrophic waters.
A distinction is made between the habitat of the spring-dwelling organisms, the crenobionts , in the eukrenal , the actual source area, and the hypocrenal , the adjoining habitat in the upper spring outlet. The hypocrenal reaches only as far as the living conditions of the source flow are still shaped by the water outlet. If organisms predominantly inhabit the krenal , they are referred to as krenophiles , but if they rarely appear there, they are called krenoxene .
- The Aachtopf is with a bed from 1,300 to 24,000 liters per second, the most water-rich German source. Here mainly water from the sinking of the Danube comes to light again.
- The Blautopf is a karst spring of a similar size near Blaubeuren .
- The warmest thermal springs in Germany with a temperature of 74 ° C are located in Burtscheid near Aachen .
- In the Pader spring area in downtown Paderborn, 3,000 to 9,000 liters of water per second push to the surface of the earth in over 200 small springs in several walled spring basins.
- The Rhume spring is the most abundant spring in northern Germany with a spring discharge of an average of 2,000 liters per second and is fed by water from the Harz Mountains .
- The Lutter spring is located on the Elm in northern Germany.
- The source of the Lahn is located in the Rothaargebirge in the cellar of an old mill house.
- The 20-tube fountain in Altleiningen is the strongest fissure spring in the Palatinate. The water emerges from a crevice, is first captured in two large well chambers and then gushes out of 20 parallel tubes. The amount of water flow is controlled with a very well thought-out system of groundwater impoundment (for the construction period).
- The Salzaspring is the source of the Salza and with a discharge from the Karst averaging 704 liters per second, it is the most productive spring in Thuringia.
- The Schwarzbach rises from the active Schwarzbachloch water cave . The karst spring is located in the Berchtesgadener Land district , and its discharge fluctuates widely between 30 and 17,000 liters per second.
- Leutra spring in Weimar , the so-called ox eye or the spring spring is one of the three partial springs of the Leutrabach in the park on the Ilm .
- Pießling origin : One of the strongest karst springs in Austria near Spital am Pyhrn in the Totes Gebirge ( Upper Austria ). The river it feeds flows into the Teichl after about 7 kilometers and later into the Steyr .
- Waterhole : karst spring in Austria in the Salzatal near Palfau ( Styria ). After exiting a cave and crossing under a natural rock gate, the water masses plunge over numerous waterfalls and cascades about 350 m into the depth and form the tourist attraction of the Wasserlochklamm .
- Healing springs for cold water cure in St. Radegund ( Styria ), which were developed by mainly Hungarian nobles under Gustav Novy (1830–1896) and Gustav Ruprich (1855–1912). Examples: Rosa-Quelle, Source des paresseux, Eremitenquelle.
- Runny wall : a large area leaving source in the Steyr canyon in Molln .
- Rheinquelle : After hydrological features, it is difficult to determine "the" source of the Rhine. Lake Toma in the canton of Graubünden is often seen as the source of the Rhine . The source furthest from the mouth is the Rein da Medel spring in the canton of Ticino .
- Siebenbrünnen , the origin of the Simme near Lenk .
- Rinquelle on Lake Walen, rises in the lower part of the Seerenbach Falls with the highest single fall in Switzerland.
- Alois Döring: sources. In: Reallexikon der Germanischen Altertumskunde (RGA). 2nd Edition. Volume 24, Walter de Gruyter, Berlin / New York 2003, ISBN 3-11-017575-4 , pp. 11–15. (Introductory specialist article on the history, archeology and onomatology of the source)
- Britt-Marie Näsström, Wolf-Rüdiger Teegen: Spring shrines and spring cult. In: Reallexikon der Germanischen Altertumskunde (RGA). 2nd Edition. Volume 24, Walter de Gruyter, Berlin / New York 2003, ISBN 3-11-017575-4 , pp. 15-29.
- PDF document of the TU Dresden with a description of the various source types and further literature
- Four-source area of the Fichtel Mountains / Northeast Bavaria
- Source types in the lexicon of geosciences (www.spektrum.de)
- Ernst Neef 1981: The face of the earth. P. 525.
- About 20% of the ice-free land areas worldwide are exposed carbonate rocks, Ford & Williams, Karst Hydrogeology and Geomorphology, Chichester 2007, p. 5.
- Frank Ahnert: Introduction to Geomorphology. Eugen Ulmer Verlag, Stuttgart (utb Volume 8103). 5th edition, 2015. ISBN 978-3-8252-8627-9 , p. 158.