While in English and in theRomance languages, the lake is named after the city ofConstance, the German name derives from the village of Bodman (municipality ofBodman-Ludwigshafen), in the northwesternmost corner of the lake.
Lake Constance is located along theRhine between theAlpine Rhine, its maintributary, and theHigh Rhine, its outflow. It is thethird largest freshwater lake by surface area in Central and Western Europe (and the second largest in volume), afterLake Geneva and (in surface area)Lake Balaton.
It is 63 km (39 mi) long, and, nearly 14 km (8.7 mi) at its widest point. It covers about 536 km2 (207 sq mi), and is 395 m (1,296 ft) abovesea level. Its greatest depth is 252 metres (827 ft), exactly in the middle of the Upper Lake. Its volume is about 48 km3 (12 cu mi).[1]
The lake has two parts. The main east section, calledObersee or "Upper Lake", covers about 473 square kilometres (183 sq mi), including its northwestern arm, theÜberlinger See (61 km2 (24 sq mi)), and the smaller west section, calledUntersee or "Lower Lake", with an area of about 63 square kilometres (24 sq mi).[1][3]
The connection between these two lakes is theSeerhein (lit.: "Rhine of the Lake(s)"). Geographically, usually it is not considered to be part of the lake, but a very short river.[1][4]
The Lower Lake Constance is loosely divided into three sections around theIsland of Reichenau. The two German parts, theGnadensee (lit.: "Lake Mercy") north of the island and north of the peninsula of Mettnau (theMarkelfinger Winkel), and theZeller See, south of Radolfzell and to the northwest of the Reichenau island, and the mainly SwissRheinsee (lit.: "Lake Rhine") – not to be mistaken for theSeerhein (lit.: "Rhine of the Lake(s)") at its start – to the south of the island and with its southwestern arm leading to its effluent inStein am Rhein.[1][3]
The water of theregulated Alpine Rhine flows into the lake in the southeast nearBregenz, Austria, then through the Upper Lake Constance hardly targeting theÜberlinger See, into theSeerhein in the town ofKonstanz, then through theRheinsee virtually without feeding both German parts of the Lower Lake, and finally feeds the start of theHigh Rhine in Swiss townStein am Rhein.[1][5][3]
The lake itself is an important source of drinking water for southwestern Germany.
The culminating point of the lake's drainage basin is the Swiss peakPiz Russein of the Tödi massif of theGlarus Alps at 3,613 metres (11,854 ft) above sea level. It starts with the creekAua da Russein (lit.: "Water of the Russein").[6]
Lake Constance was formed by theRhine Glacier during theQuaternary glaciation ice age and is aZungenbecken or Tongue lake. After the end of thelast glacial period, about 10,000 years ago, the Obersee and Untersee still formed a single lake. Thedownward erosion of theHigh Rhine caused the lake level to gradually sink and a sill, theKonstanzer Schwelle, to emerge.
The Rhine, theBregenzer Ach, and theDornbirner Ach carry sediments from theAlps to the lake, thus gradually decreasing the depth and reducing the extension of the lake in the southeast.
In antiquity, the two lakes had different names; later, for reasons which are unknown, they came to have the same name.
In the 19th century, there were five different localtime zones around Lake Constance. Constance, belonging to theGrand Duchy of Baden, adhered toKarlsruhe time, Friedrichshafen used the time of theDuchy of Württemberg, in Lindau, the Bavarian Munich time was observed, and Bregenz used Prague time, while the Swiss shore used Berne time. One would have needed to travel only 46 kilometres (29 mi) to visit five time zones. Given the amount of trade and traffic over Lake Constance, this led to serious confusion. Public clocks in harbors used three different clock faces, depending on the destinations offered by the boat companies. In 1892, all German territories usedCET, the Austrian railways had already introduced CET the previous year and Switzerland followed in 1894. Because traffic timetables had not been yet updated, CET became the sole valid time around and on Lake Constance in 1895.[7]
The earliest recorded reference to the lakes is byRoman geographerPomponius Mela around AD 43, calling the upper lakeLacus Venetus and the lower lakeLacus Acronius, the Rhine passing through both. Around AD 75, the naturalistPliny the Elder called them bothLacus Raetiae Brigantinus after the main Roman town on the lake,Brigantium (later Bregenz). This name is associated with theCelticBrigantii who lived here, although it is not clear whether the place was named after the tribe or the inhabitants of the region were named after their main settlement.Ammianus Marcellinus later used the formLacus Brigantiae.[8]
The current German name ofBodensee derives from the place nameBodman, which probably originally derived from theOld High Germanbodamon which meant "on the soils", indicating a place on level terrain by the lake.[9]: 500 This place, situated at the west end of Lake Überlingen (Überlinger See), had a more supraregional character for a certain period in theearly Middle Ages as aFrankishimperial palace (Königspfalz),Alamannian ducal seat andmint, which is why the name may have been transferred to the lake ("lake, by which Bodman is situated" =Bodmansee). From 833 or 834, in Latin sources, the name appears in itsLatinised formlacus potamicus.[10] Therefore, the name actually derived from the BodmanPfalz (Latinized asPotamum) was wrongly assumed by monastic scholars likeWalahfrid Strabo to be derived from the Greek wordpotamos for "river" and meant "river lake". They may also have been influenced by the fact that the Rhine flowed through the lake.[9]: 501ff
Wolfram von Eschenbach describes it inMiddle High German as theBodemensee orBodemsee[11] which has finally evolved into the present German name,Bodensee. The name may be linked to that of theBodanrück, the hill range between Lake Überlingen and the Lower Lake, and the history of theHouse of Bodman.
Location of Lake Constance within the Duchy of Swabia (yellow), 911–1268
The German name of the lake,Bodensee, has been adopted by many other languages, for example: Dutch:Bodenmeer, Danish:Bodensøen, Norwegian:Bodensjøen, Swedish:Bodensjön, Finnish:Bodenjärvi, Russian:Боденское озеро, Polish:Jezioro Bodeńskie, Czech:Bodamské jezero, Slovak:Bodamské jazero, Hungarian:Bodeni-tó, Serbo-Croatian:Bodensko jezero, Albanian:Liqeni i Bodenit.
After theCouncil of Constance in the 15th century, the alternative nameLacus Constantinus was used in the (Roman Catholic) Romance language area. This name, which had been attested as early as 1187 in the formLacus Constantiensis,[8] came from the town of Konstanz at the outflow of the Rhine from the Obersee, whose original name, Constantia, was in turn derived from the Roman emperor,Constantius Chlorus (around 300 AD). Hence the French:Lac de Constance, Italian:Lago di Costanza, Portuguese:Lago de Constança, Spanish:Lago de Constanza, Romanian:Lacul Constanța, Greek:Λίμνη της Κωνσταντίας – Limni tis Konstantias. The Arabic, بحيرة كونستانسbuħaira Konstans and the Turkish,Konstanz gölü, probably go back to the French form of the name. Even in Romance-influenced English the name "Lake Constance" gained a foothold and was then exported into other languages such as Hebrew: ימת קונסטנץyamat Konstanz and Swahili:Ziwa la Konstanz. In many languages both forms exist in parallel e.g.Romansh:Lai da Constanza andLai Bodan, Esperanto:Konstanca Lago andBodenlago.[citation needed]
The poetic name, "Swabian Sea", was adopted by authors of theearly modern era and theEnlightenment from ancient authors, possiblyTacitus. However, this assumption was based on an error (similar to that of theTeutoburg Forest and theTaunus): the Romans sometimes used the nameMare Suebicum for theBaltic Sea, not Lake Constance. In times when the Romans had located the so-called "Suebi", then anElbe Germanic tribe near a sea, this was understandable. The authors of theEarly Modern Period overlooked this and adopted the name for the largest lake in the middle of the formerDuchy of Swabia, which also included parts of today's Switzerland.[12] Today the name Swabian Sea (Schwäbisches Meer) is only used jocularly as a hyperbolic term for Lake Constance.[13]
SaintsColumbanus andGallus on Lake Constance, from a 15th-century manuscript
NoPaleolithic finds have been made in the immediate vicinity of the lake, because the region of Lake Constance was long covered by theRhine Glacier. The discovery of stone tools (microliths) indicate thathunters and gatherers of theMesolithic period (Middle Stone Age, 8,000–5,500 BC) frequented the area without settling, however. Only hunting camps have been confirmed. The earliest Neolithic farmers, who belonged to theLinear Pottery culture, also left no traces behind, because the Alpine foreland lay away from the routes along which they had spread during the 6th millennium BC.[14] This changed only in the middle and lateNeolithic when shore settlements were established, the so-calledpile dwelling andwetland settlements, which have now been uncovered mainly on Lake Überlingen, theConstance Hopper and on the Obersee. AtUnteruhldingen, a pile dwelling village has been reconstructed, and now forms an open air museum.In 2015, a 20 km line of about 170 man-madeunder-water stone mounds [de] dated in the Neolithic period or early Bronze Age was discovered on the south-west shore of the lake between Bottighofen and Romanshorn.[15][16][17][18][19]
Grave finds fromSingen am Hohentwiel date to the beginning of the EarlyBronze Age and shore settlements were repeatedly built during theNeolithic Period and the Bronze Age (up to 800 BC). During the followingIron Age the settlement history is interrupted. The settlement of the shore of Lake Constance during theHallstatt period is attested bygrave mounds, which today are usually found in forests where they have been protected from the destruction by agriculture. Since the late Hallstatt period, the peoples living on Lake Constance are referred to as theCelts. During theLa Tène period from 450 BC, the population density decreases, as can be deduced partly due from the fact that no more grave mounds were built. For the first time, written reports on Lake Constance have survived. Thus, we learn that theHelvetians settled by the lake in the south, theRhaetians in the area of theAlpine Rhine Valley and theVindelici in the north-east. The most important places on the lake wereBregenz (CelticBrigantion) and today'sConstance.
In the course of the RomanAlpine campaign of 16/15 BC, the Lake Constance region was integrated into theRoman Empire. During the campaign, there was also supposed to have been abattle on Lake Constance. The geographer,Pomponius Mela, makes the first mention in 43 AD of Lake Constance as two lakes – theLacus Venetus (Upper Lake) and theLacus Acronius (Untersee) – with the Rhine flowing through both.Pliny the Elder referred to Lake Constance asLacus Brigantinus for the first time. The most important Roman site was Bregenz, which soon became subject to Roman municipal law and later became the seat of the Prefect of the Lake Constance fleet. The Romans were also inLindau, but settled only on the hills around Lindau as the lakeshore was swampy. Other Roman towns wereConstantia (Constance) andArbor Felix (Arbon).
After the borders of the Roman Empire were drawn back to the Rhine boundary in the 3rd century BC, the Alemanni gradually settled on the north shore of Lake Constance and, later, on the south bank as well. After the introduction ofChristianity, the cultural significance of the region grew as a result of the founding ofReichenau Abbey and theBishopric of Constance. Under the rule of theHohenstaufens,Imperial Diets (Reichstage) were held by Lake Constance. In Constance, too, a treaty was drawn up between the Hohenstaufen emperor and theLombard League. Lake Constance also played an important role as a trading post for goods being traded between German and Italian states.
During theThirty Years' War, there were various conflicts over the control of the region during theLake War (1632–1648).
After theWar of the Second Coalition (1798–1802), which also affected the region and during which Austrian and Frenchflotillas operated on Lake Constance, there was a reorganisation of state relationships.
1555: the map of the route of the Rhine (Rhinelaufkarte) byCaspar Vopel includes a topographical map of Lake Constance with its larger towns, the tributaries and the course of the Rhine.[citation needed]
1633: the Swabian map byJohannes Janssonius, Amsterdam:Totius Sveviae novissima tabula shows Lake Constance with islands, tributaries, towns and villages.[20]
1675: The Lake Constance map,Lacos Acronianus sive Bodamicus, by Nikolaus David Hautt based on Andreas ArzetSJ shows Lake Constance with the adjacent lands.[21]
Lake Constance is located in the foothills of theAlps. The shore length of both main lakes is 273 kilometres (170 mi) long. Of this, 173 kilometres (107 mi) are located in Germany (Baden-Württemberg 155 kilometres or 96 miles,Bavaria 18 kilometres or 11 miles), 28 kilometres (17 mi) run through Austria and 72 kilometres (45 mi) through Switzerland.[22] If the upper and lower lakes are combined, Lake Constance has a total area of 536 km2 (207 sq mi), the third largest lake inCentral Europe by area afterLake Balaton (594 km2 or 229 sq mi) andLake Geneva (580 km2 or 220 sq mi). It is also the second largest by water volume (48.5 km3 or 11.6 cu mi or 39,300,000 acre⋅ft)[23] after Lake Geneva (89 km3 or 21 cu mi or 72,000,000 acre⋅ft) and extends for over 69.2 kilometres (43.0 mi) betweenBregenz andStein am Rhein. Itscatchment area is around 11,500 km2 (4,400 sq mi), and reaching as far south asLago di Lei in Italy.[24]
The area of theObersee, or Upper Lake, is 473 km2 (183 sq mi). It extends from Bregenz toBodman-Ludwigshafen for over 63.3 kilometres (39.3 mi) and is 14 kilometres (8.7 mi) wide betweenFriedrichshafen andRomanshorn. At its deepest point betweenFischbach andUttwil, it is 251.14 metres (824.0 ft) deep.
Lake Constance with the Island of Lindau seen from thePfänder in 2007
The three small bays on theVorarlberg shore have their own names: the Bay of Bregenz, offHard andFußach is the Bay of Fussach and, west of that is the Wetterwinkel. Farther west, now in Switzerland, is the Bay of Rorschach. To the north, on the Bavarian side, is the Bay of Reutin. The railway embankment from the mainland to the island of Lindau and the motorway bridge over the lake border the so-called Little Lake (Kleiner See), which is located between the Lindau village of Aeschach and the island.
The northwestern, finger-shaped arm of the Obersee is called Überlinger See (or Überlingersee inSwiss Standard German), orLake Überlingen. It is sometimes regarded as a separate lake, the boundary between Lake Überlingen and the rest of the Upper Lake runs approximately along the line between the southeast tip of Bodanrück (theHörnle, which belongs to the town of Konstanz) and Meersburg. TheConstance Hopper lies between the German and Swiss shores east ofKonstanz.
The Obersee and Untersee are connected by theSeerhein.
TheUntersee, or Lower Lake, which is separated from the Obersee and from its north-west arm, the Überlinger See, by the large peninsula ofBodanrück, has an area of 63 km2 (24 sq mi). It is strongly characterised and divided into different areas byend moraines, variousglacial snouts andmedial moraines. These various areas of the lake have their own names. North ofReichenau Island is theGnadensee. West of the island of Reichenau, between the peninsula ofHöri and the peninsula ofMettnau is the Zeller See (or Zellersee in Swiss Standard German), orLake Zell. North of the peninsula and swamp land Mettnau lies the lake part Markelfinger Winkel. Thedrumlins of the southern Bodanrück continue along the bed of these northern parts of the lake. South of the Reichenau, fromGottlieben toEschenz, stretches theRheinsee (lit.: "Rhine Lake") with strong Rhine currents in places. Previously this lake part was named Lake Bernang after the village ofBerlingen. On most of the maps the name of theRheinsee is not shown, because this place is best suited for the name of the Untersee.[25]
Lake Constance on the Swiss National Map (1:50'000)
Behind the present impressive traces of theWürm Ice Age, the effects of older cold periods can no longer be explored in any detail. Lake Constance now represents, above all, azungenbecken orglacial lake of the Würm Glaciation.[26]
During a later phase of the ice age, only the Obersee was glaciated. As the glacier retreated further, theglacial meltwaters flowed out of the emerging Überlingen See through the older more northerly valley into the present High Rhine valley.
Due to the advancing headward erosion, the present course of the High Rhine was finally (again) reconnected to Lake Constance.[27]
Like any glacial lake, Lake Constance will also silt up bysedimentation. This process can best be observed at the mouths of the larger rivers, especially that of the Alpine Rhine. Thesilting up process is accelerated by ever-increasing erosion by the Rhine and the associated reduction in the level of the lake.
Because the Alpine Rhine brings with itdrift from the mountains and deposits this material assediment, the Bay of Bregenz will silt up in a few centuries time. The silting up of the entire Lake Constance is estimated to take another ten to twenty thousand years.
The outflow of the Untersee is theHigh Rhine with theRhine Falls atSchaffhausen. Both the average precipitation of 0.45 km3/a and evaporation which averages 0.29 km3/a cause a net change in the level of Lake Constance that is less when compared to the influence of the inflows and outflows.[23] Further quantities of lake water are extracted by municipal waterworks around the lake and the water company ofBodensee-Wasserversorgung.
The island ofLindau is located in the east of the Obersee, and is the second largest island. On it is the old town and main railway station of Lindau.
The third largest island isMainau in the southeast of Lake Überlingen. The owners, the family ofBernadotte, have set up the island as a tourist attraction and created botanical gardens and wildlife enclosures.
Relatively large, but uninhabited and inaccessible because of their status as nature reserves, are two islands off theWollmatinger Ried: theTriboldingerbohl which has an area of 13 ha (32 acres) and Mittler or Langbohl which is just three hectares (7.4 acres) in area.
Smaller islands in the Obersee are:
Dominican Island (Dominikanerinsel) separated by a six-metre-wide ditch from the old town ofConstance which is home to the Steigenberger Hotel (two hectares [4.9 acres])
In Lake Constance there are several peninsulas which vary greatly in size:
TheBodanrück, the largest peninsula, separates the Überlinger See (Obersee) from the Untersee. It covers an area of 112 km2 (43 sq mi).
TheMettnau in the Untersee, which extends towards the Island of Reichenau, separates Zeller See in the south from the Markelfinger Winkel in the north. It has a surface area of 1.7 km2 (0.66 sq mi).
TheHöri, (about 45-square-kilometres) also extends towards the Island of Reichenau, and separates the Zeller See to the north from the Rheinsee to the south.
In the southeast, near the mouth of the new Rhine Canal, theRohrspitz juts out about 1.2 km (0.75 mi) into the lake and forms the western perimeter of the Bay of Fußach. It has an area of about 50 hectares.
TheWasserburg peninsula has a castle, Schloss Wasserburg, and the parish church of St. George. The peninsula is on the northeastern shore of the Obersee between the Bay of Nonnenhorn in the west and Bay of Wasserburg in the east. It has an area of 2.3 ha (5.7 acres) and was an island until 1720, when theFuggers built a causeway. In March 2009, 27 people lived on the peninsula.
TheGalgeninsel ("Gallows Island") in the Bay of Reutin is also a peninsula that was formerly an island. It is only 0.16 hectares in area.
The shores of Lake Constance consist mainly of gravel. In some places there are also sandy beaches, such as theRohrspitz in the Austrian section of the lake, theLangenargen andMarienschlucht.
According to the data of the International Water Protection Commission for the Lake Constance, the approximate shore length is 273 km (170 mi) (seeCoastline paradox). The inflow of water is constantly changing, mainly due to rain and the snow melt in the Alps. Its average surface area is about395 m above NN (in Switzerland the absolute value is slightly higher in m above sea level). The more or less regular seasonal fluctuations in the water level also lead to slight variations in shore length and differences in the shore zone habitats (depending on high and low water).
Additionally,car ferries link Romanshorn to Friedrichshafen, and Konstanz to Meersburg.[2][3] Between 1869 and 1976, there used to betrain ferries across the lake.
Several smaller harbors on the Upper Lake offer boat trips along the German or Swiss coast (with one continuing over theOld Rhine toRheineck).
The climate of the Lake Constance area is characterised by mild temperatures with moderate gradients, thanks to the balancing and retarding effect of the large body of water.
It has asubtropical microclimate, which allows the cultivation of some exotic fruits and trees. Constance counts 2069 sunshine hours a year and is therefore considered one of the sunniest cities in Germany.
Winters are generally short and mild, although night temperatures can fall under 0°C, especially from December to February. Typically day temperatures range between +5 and +12°C, while nights with +1 to +8°C on average stay cold, though mostly without long and severe frosts.
TheFöhn, a warm wind from theMediterranean Sea, that regularly blows through the Alps, can cause temperatures between 15 and 20°C with sunshine for several days, while on the other hand fog creates a few cold days between 1 and 5°C each year. Generally, Lake Constance is affected more by fog than neighboring regions more inland.
Spring goes from March to May and is usually sunny, with day temperatures between 15 and 22°C but still relatively cold water. This is also resulting in still cold night temperatures that range between 4°C in March and 12°C in May only.
As the lake temperature heats up by the increasing warm days, the nights are also becoming milder, though moderated a little bit by the height and lake. This results in average morning lows of 16-18°C during the high summer months. Lake Constance counts one of the highest amount oftropical nights in Germany (lowest temperature at 20°C or more).
The days in Summers (June-September) are warm to hot with day temperatures of 26-33°C on average, decreasing to around 20°C until the end of September. Humidity levels raise noticeable and temperatures often move up to 35°C between June and August. This increases theheat index, causing Lake Constance to have a stressful climate.
The region receives most of its sunny days during high summer. In the recent years, in 2018 and 2022, the water levels fall to new record lows due to weeks without significant rain. On the other hand, the closeness to the Alps can cause thunderstorms in the evenings that sometimes occur out of nowhere.
While the official bathing season ends in September, the average lake temperature stays around 20°C until October. Autumn is generally the time when Lake Constance starts to experience more foggy mornings again, but the day temperatures still range between 21 in the beginning and 10-12°C at the end of the season. Night temperatures fall from 13°C in September to an average of 5°C in November.
Lake Constance is one of the best known wine growing regions in Germany and experiences several outdoor events during harvest time in autumn.
Waves raised by Föhn winds
Lake Constance is also considered to be a risky and challenging lake for water sports because of the danger of gusty winds which can whip up waves as the weather changes suddenly. The most dangerous wind is the föhn, a warm down-slope wind from the Alps, which spreads out across the water, especially through theAlpine Rhine Valley and can generate waves several metres high.
Similarly dangerous for those unfamiliar with the area, are the sudden stormy gusts of wind during summer thunderstorms. They constantly claim victims from the water sports fraternity. During a thunderstorm in July 2006, waves reached heights of up to 3.50 metres.
For these reasons, there is a storm warning system in all three neighbouring countries. Forstorm warning purposes, Lake Constance is divided into three warning regions (west, centre and east). Warnings can be issued for each region independently. A "high winds" warning will be issued whensqualls are expected of between 25 and 33 knots or registeringforce 6 to 8 on theBeaufort scale. Agale warning announces the likelihood of gale-force winds, i.e. those at speeds as of 34 knots or more or force 8 on the Beaufort scale. In order to issue these warnings, orange-coloured flashing lights are installed around the lake, which flash at a frequency of 40 times per minute for high winds or 90 times per minute for gales. It can happen that, due to the differently regulated responsibilities and assessments, a gale warning is issued on the Swiss side of the Obersee, but not on the German or Austrian shores, and vice versa. Ships and ferries on Lake Constance indicate a gale warning by hoisting aSturmballon ("storm ball") up the mast.
Frozen lake surface: skating in theMarkelfinger WinkelFreezing of Lake Constance in 1963
A one-hundred year event is the freezing over of Lake Constance, when the Lower Lake and the Upper Lake are completely frozen over so that people can safely cross the lake on foot. The last so-calledSeegfrörne (Alemannic) event was in 1963. The following is a list ofyears in which Lake Constance froze over partially or completely:[34][35]
Certain parts of the lake freeze over more frequently, mainly due to their shallow depth of water and shelter, as is the case, for example, of the so-calledMarkelfinger Winkel between the municipality ofMarkelfingen and theMettnau peninsula.
A100-year flood around June 1999 (Pfingsthochwasser 1999) raised the level about 2 metres above normal, flooding harbors and many shoreline buildings and hotels.
In late August 2005, heavy rain raised the level by more than 70 cm (28 in) in a few days. The rains caused widespread flooding and washed out highways and railroads.
Frequent rainfall and snowmelt in the summer of 2024 raised water levels to 68 cm (27 in) above normal level.
The lake lies where the countries of Austria, Germany, and Switzerland meet.[36] Beyond areas less than 25 m (82 ft) deep, considered to be under the jurisdiction of the nearest country, there is no legally binding agreement as to where the borders lie between the three countries.[36][37] However, Switzerland holds the view that the border runs through the middle of the lake, Austria is of the opinion that the contentious area belongs to all the states on its banks, which is known as a "condominium", and Germany holds an ambiguous opinion.[36][38] Legal questions pertaining to ship transport and fishing are regulated in separate treaties.
Disputes occasionally arise. One concerns ahouseboat which was moored in two states (ECJ c. 224/97 Erich Ciola); another concerns the rights to fish in the Bay of Bregenz. In relation to the latter, an Austrian family was of the opinion that it alone had the right to fish in broad portions of the bay. However, this was accepted neither by the Austrian courts nor by the organs and courts of the other states.[39]
Until the 19th century, Lake Constance was a natural lake. Since then, nature has been heavily influenced byclearing and the cultivation of much of the land around its shores. However, some near-natural areas have been largely conserved, especially in the nature reserves, or were re-naturalised. As a result, the Lake Constance region has some unusual ecological features. These include the large forested area on theBodanrück, the occurrence ofmarsh gentian andorchids of the generaDactylorhiza andOrchis in the Wollmatinger Ried, and theSiberian iris (Iris sibirica) in theEriskircher Ried, which was therefore given its own name.[40] One unique species among the local flora is theLake Constance forget-me-not (Myosotis rehsteineri), whose habitat is restricted to undisturbed limestone gravel beaches.
Lake Constance is also the home of numerous bird species, many of which nest in its nature reserves, such as theWollmatinger Ried or theMettnau peninsula. 412 species have so far been recorded.[41]
In December 2014, 1,389cormorant were counted. The International Lake Constance Fishery Association (IBF) estimates the food requirements of the cormorants on Lake Constance at 150 tonnes of fish annually.[45]
Lake Constance is an important overwintering area for around 250,000 birds.[46] annually. Bird species such as thedunlin, thecurlew and thelapwing overwinter at Lake Constance.[47] In the middle of December 2014 there were 56,798 heron, 51,713 coot and 43,938 pochard.[45] In November/December are about 10,000 to 15,000red-crested pochard and 10,000 great crested grebe on Lake Constance.[48]
During migration in late autumn there are also numerousloons on the lake (black-throated andred-throated loon, as well as a fewgreat northern loons). Lake Constance is also very important as a staging post during thebird migration. Bird migration is often inconspicuous and most noticeable when there are special weather conditions that make day migration obvious. Only where there is a prolonged spell of widespread low-pressure is it common to observe the congestion of large groups of migratory birds. This can often be observed in autumn on theEriskircher Ried on the northern shore of Lake Constance. This is where broad front migration converges on the lake and birds then try to move along the shore towards the northwest. The importance of Lake Constance as an important area for resting and overwintering is underlined by the Max Planck Institute for Ornithology's Radolfzell Bird Observatory (Vogelwarte Radolfzell), which is thebird ringing centre for the German states of Bavaria, Baden-Württemberg, Berlin, Rhineland-Palatinate and the Saarland as well as for Austria, and which researches bird migration.[49]
Around 45 species of fish live in Lake Constance. The annual haul from fishing is 1.5 million kg. Unusual species occurring here considering the location of the lake are thewhitefish (Coregonus spec.) and theArctic char (Salvelinus alpinus). Fish that are important for the fishing industry are:
Lake trout (German:Seeforelle, Lat.:Salmo trutta lacustris)
The Bodenseefelchen (Coregonus wartmanni), which was named after Lake Constance due to the great numbers found there, is often prepared whole or as a fillet, in the style of the miller's wife (nach Müllerin Art), in local fish restaurants in a similar way to other trout[51] It is also often served smoked.
Twoendemic species are known to have existed only in Lake Constance, theBodensee-Kilch (Coregonus gutturosus) anddeepwater char (Salvelinus profundus). The former is now assumed to be extinct, while the latter was feared extinct for decades until its rediscovery in the 2010s.[52][53]
For many yearsnon-native species have settled in the Lake Constance ecosystem and, in some cases, endangered or threatened native flora and fauna. At Lake Constance, non-native species have been increasing annually. Several have been transported from other waterbodies as 'stowaways' on the outside of boats, life jackets, anchor chains or ropes or diving gear.[54] Others have immigrated from theBlack Sea or theDanube since the opening of theMain-Danube Canal. Others have been deliberately introduced.[55]
Even therainbow trout (Oncorhynchus mykiss) is not a native fish. It was introduced into Lake Constance around 1880 for economic reasons to enhance the local fauna.[56]
Among the foreign species of animal in Lake Constance are thezebra mussel (Dreissena polymorpha) which, since the 18th century, has spread from the Black Sea region across most of Europe and was carried into Lake Constance between 1960 and 1965. After a huge increase in numbers during the 1980s in the Rhine and large lakes, this species is now in retreat today. The zebra mussel causes problems because, among other things, it blocks water extraction pipes. In addition, the species can be a disaster for domestic shellfish, because it competes for their food.[57] Today, according to the Institute for Lake Research (Institut für Seenforschung, ISF), the zebra mussel is also an important food for overwintering waterfowl. In fact, the number of overwinterers has more than doubled in around 30 years.[56]
Thekiller shrimp (Dikerogammarus villosus) has spread since 2002 from two sections of shoreline near Hagnau and Immenstaad, over the whole Lake Überlingen (2004), the whole of the Upper Lake (2006) and almost the whole Lake Constance and Rheinsee shore (2007).[58] As its name implies, it is a voracious burglar of fish larvae and fish eggs.[56]
The most recent example is the littleopossum shrimp (Limnomysis benedeni), only six to eleven millimeters long, which was found in 2006 in the Vorarlberg region of Hard, and can now be found almost all over Lake Constance.[56] It comes from the waters around the Black Sea. It was presumably first transported by ships up the Danube before it spread into the Rhine river system and entered Lake Constance. The opossum shrimp, which occurs in many places in shoals of several million in winter, are already an influential link in the food chain in Lake Constance. They consume dead animal and plant material as well asphytoplankton, but are also eaten by fish themselves.[57]
Today, in western Lake Constance are found: the North Americanspinycheek crayfish (Orconectes limosus), which was introduced into European waters in the mid-19th century to increase the yield,[56] occasionally theChinese mitten crab (Eriocheir sinensis), and in the lake's tributaries, thesignal crayfish (Pacifastacus leniusulus). As these species of large crayfish are immune tocrayfish plague, but spread the pathogen, they are a great danger to native species such asnoble crayfish,white-clawed crayfish orstone crayfish. The animals are often undemanding, multiply rapidly and lead predatory lives, thus also posing a threat to various small species of fish.[57] The ISF has been systematically researching the subject since 2003.[56]
After a collision with theStadt Zürich in 1864 thewreck of theJura has lain on the lake bed at a depth of 45 metres off the Swiss shore. In the early 20th century four ships were sunk in the Obersee after being taken out of service: in 1931 theBaden, formerly theKaiser Wilhelm, in 1932 theHelvetia, in 1933 theSäntis and in 1934 theStadt Radolfzell. The hull of the burnt-outFriedrichshafen was scuttled in 1944 off the mouth of theArgen in 100 to 150 metres of water.[59][60]
The tourism and leisure industry is important for this region. Overnight stays reached 17,56m visitors in 2012 with a turnover of about 1.9bn Euros. The same amount comes from the 70 million visitors that visit Lake Constance each year.[61]
Eastern part of Upper Lake Constance seen from Spot satellite.
This region is known for sightseeing, water-sports, winter-sports likeSkiing, summer-sports likeSwimming (sport),Sailing and recreation. It is also one of the few places where modernZeppelin airships operate and 12–14 people can take a trip above the lake around various points of interest.[62]
In cooperation with tourism service providers, tourism organizations and public institutions in Germany, Austria, Switzerland andLiechtenstein, the International Bodensee Tourismus GmbH (IBT GmbH)[63] is responsible for the tourism marketing of the Lake Constance region.
TheHegau region adjacent to Lower Lake Constance (Untersee) contains several higher mountains of volcanic origin, many with ruins of fortresses on their tops (e.g.Hohenkrähen,Mägdeberg). The southernly located of these Hegau volcanoes (e.g.Hohentwiel) also offer a view over the lakes.
Since 2001, the ART BODENSEE takes place inDornbirn. It is an annual meeting point for the exchange between collectors, artists and art appreciators.[65]
Biking around the lake is also possible on the 261 km (162 mi) long trail called "Bodensee-Radweg". It brings its visitors to the most interesting sites and goes around the whole lake. Nevertheless, various shortcuts via ferries allow shorter routes and the trail is suitable for all levels.[66] Note: There is also a trail that goes by the name "Bodensee-Rundweg".[67] This road was intended for pedestrians so biking is sometimes not suitable or allowed.
The 260 kilometers long Lake Constance circular route, signposted as "Bodensee Rundwanderweg", leads around Lake Constance through the territories of Germany, Austria and Switzerland. It is mainly intended for hiking; cyclists follow the sometimes slightly different managed Lake Constance cycle path.[68] The trail can be walked in smaller stages of various lengths and offers nice views of the lake, landscape and wildlife. However, due to industrial settlements, buildings and nature reserves, not all the coastal zones are readily accessible. Furthermore, in the estuary of the rivers, such theLeiblach,Bregenzer Ach,canalized Rhine andOld Rhine (Fußacher breakthrough), considerable distances have to be covered inland to the next bridge or river crossing point. Due to busy riverside roads, the Bodensee-Rundweg sometimes runs as a trail above the lake with some lookout possibilities.
the UpperSwabian pilgrimage-route of St. James, which leads from Upper Swabia to the lake and branches north of the lake both in the direction ofNonnenhorn and in the direction ofMeersburg
the Bavarian-Swabian route of St. James, which leads down from the WestAllgäu to the lake
the Schwabenweg, which ensures the connection to Switzerland to the lake nearKonstanz[71]
Swimming in the lake is usually best from mid-June to mid-September. Depending on the weather and exact location, the water temperatures reach 20 to 27 °C (68.0 to 80.6 °F). Within one day, differences of up to 3 °C (5.4 °F) are possible with appropriate sunlight, so that the lake invites to swim, especially on warm summer evenings.[72]
Diving in Lake Constance is considered attractive and challenging. Most of the diving areas are located in the northern part of the lake (Überlingen,Bodman-Ludwigshafen,Marienschlucht and others), a few also in the south.[73] The areas should be dived exclusively by experienced divers under the guidance of one of the local diving schools or a seasoned diver. Diving at some spots like the devils table ("Teufelstisch") called rock needle in the lake in front of the Marienschlucht, is only allowed after approval by the district office Konstanz.
For all divers, the water in Lake Constance—even in summer—is already below 10 °C (50 °F) from a depth of 10 metres (32.8 ft) which requires suitablecold-water regulators that do not freeze at such temperatures.
Pleasure boating is important. At the beginning of 2011, 57,875 amusement vehicles were registered for Lake Constance.[75]
The legal basis for all shipping on the lake is the ordinance on shipping on Lake Constance, or "Bodensee-Schifffahrtsordnung". It is monitored on Lake Constance and on the Upper Rhine by the German, Swiss and Austrian Water Police, the "Seepolizei".
All boats must be registered, and boat drivers must hold a "Bodenseeschifferpatent" (authorization to drive a patented vehicle on Lake Constance). It is issued in Germany by the shipping offices of the district of Constance, the Lake Constance district, and the district ofLindau; in Switzerland by the cantonal authorities; and in Austria by the District CommissionBregenz. For pleasure boaters short-term guest licenses are possible (for the categories A formotorboats over 4.4 kW and D forsailboats over 12 m2 sail area).
Boating events
Since 1979, every year to theassumption of Mary, Europe's largest ship procession is held on Lake Constance.[76]
The steamboat,HohentwielView from the Pfänder hill of Bregenz and the lake (with Lindau in the background)Reichenau seen from the German shoreLake Constance from LindauTwilight near ArbonThe Lower Lake (Untersee)Dingelsdorf shippingpier
The lake was frozen in the years 1077 (?), 1326 (partial), 1378 (partial), 1435, 1465 (partial), 1477 (partial), 1491 (partial?), 1517 (partial), 1571 (partial), 1573, 1600 (partial), 1684, 1695, 1709 (partial), 1795, 1830, 1880 (partial), and 1963.
About 1,000tonnes (1,100short tons) of fish were caught by 150 professional fishermen in 2001 which was below the previous ten-year average of 1,200 tonnes (1,300 short tons) per year. The Lake Constancetrout (Salmo trutta) was almost extinct in the 1980s due to pollution, but thanks to protective measures they have made a significant return. Lake Constance is the home of the critically endangered species of troutSalvelinus profundus,[79] and formerly also the nowextinct Lake Constance whitefish (Coregonus gutturosus).[80]
^abcdefghijklm"Bodensee-Daten" (in German). igkb Internationale Gewässerschutzkommission für den Bodensee. June 2004. Archived fromthe original on 1 March 2018. Retrieved28 February 2018.
^abc"28bis - Lindau" (Map).Lindau (2010 ed.). 1:100 000. National Map 1:100'000. Wabern, Switzerland: Federal Office of Topography –swisstopo. 2008.ISBN978-3-302-10028-9. Retrieved28 February 2018 – via map.geo.admin.ch.
^abArno Borst (1982). "Bodensee – Geschichte eines Wortes".Schriften des Vereins für Geschichte des Bodenseeraums (in German). 99, 100 (Heft 1981/1982). Friedrichshafen: Selbstverlag des Bodenseegeschichtsvereins.
^Rolf Zimmermann (2004).Am Bodensee (in German). Konstanz, Germany: Stadler Verlagsgesellschaft. p. 5.ISBN3-7977-0504-2.
^Wilhelm Martens (1911).Geschichte der Stadt Konstanz (in German). Konstanz, Germany: Gess. pp. 6–7.
^Karl Heinz Burmeister (2005)."Der Bodensee im 16. Jahrhundert"(PDF).Montfort, Vierteljahreszeitschrift für Geschichte und Gegenwart Vorarlbergs (in German).57 (Heft 3). Dornbirn, Austria: Vorarlberger Verlagsanstalt:228–262. Archived fromthe original(PDF) on 31 January 2012. Retrieved1 March 2018 – via vorarlberg.gv.at.
^Helmut Schlichtherle (1989). "Pfahlbauten: die frühe Besiedelung des Alpenvorlandes".Spektrum der Wissenschaft (in German). Vol. 1989, no. Siedlungen der Steinzeit. Heidelberg, Germany: Spektrum-Verlag. pp. 140 ff.ISBN3-922508-48-0.
^Leuzinger, Urs, ed. (2018)."Rätselhafte Steinstrukturen im Bodensee"(PDF) (in Swiss High German). Thurgau, Switzerland: Amt für Archäologie.Archived(PDF) from the original on 1 April 2022. Retrieved27 July 2022. (3 pages)
^Schär, Markus (11 June 2019)."Bohren nach dem Rätsel". Wissen.thurgaukultur.ch (in Swiss High German).Archived from the original on 21 June 2019. Retrieved27 July 2022.
^Bodensee-Daten. In: Internationale Gewässerschutzkommission für den Bodensee (publ.):Seespiegel. December 2011, p. 6.
^abUta Mürle, Johannes Ortlepp, Peter Rey, Internationale Gewässerschutzkommission für den Bodensee (publ.):Der Bodensee: Zustand – Fakten – Perspektiven. 2nd revised edition. Bregenz, 2004,ISBN3-902290-04-8, p. 10.
^Meichle, Friedrich (1963). "Seegfrörne und Eisprozession in Vergangenheit und Gegenwart".Schriften des Vereins zur Geschichte des Bodensees und seiner Umgebung (in German). Vol. 81. pp. 145–170.ISSN0342-2070.
^Dobras, Werner (1992).Seegfrörne: die spannende Geschichte der Seegfrörnen von 875 bis heute. 2. veränderte Auflage (in German). Konstanz: Stadler.ISBN3-7977-0266-3.
Zimmermann, Rolf (2004),A Look at Lake Constance, Konstanz, Germany: Stadler Verlagsgesellschaft,ISBN3-7977-0507-7 (Pictures and texts of the cities around Lake Constance).
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