Editing Lake Constance (section)

== Geography ==
[[File:Lake Constance from Winterstaude (East to West).JPG|thumb|Complete lake from the [[Winterstaude]]]]

=== Divisions ===
Lake Constance is located in the foothills of the [[Alps]]. The shore length of both main lakes is {{convert|273|km|mi}} long. Of this, {{convert|173|km|mi}} are located in Germany ([[Baden-Württemberg]] {{convert|155|km|mi|disp=or}}, [[Bavaria]] {{convert|18|km|mi|disp=or}}), {{convert|28|km|mi}} run through Austria and {{convert|72|km|mi}} through Switzerland.<ref>''Bodensee-Daten.'' In: Internationale Gewässerschutzkommission für den Bodensee (publ.): ''Seespiegel.'' December 2011, p. 6.</ref> If the upper and lower lakes are combined, Lake Constance has a total area of {{convert|536|km2|sqmi|abbr=on}}, the third largest lake in [[Central Europe]] by area after [[Lake Balaton]] ({{convert|594|km2|sqmi|abbr=on|disp=or}}) and [[Lake Geneva]] ({{convert|580|km2|sqmi|abbr=on|disp=or}}). It is also the second largest by water volume ({{convert|48.5|km3|cumi acre.ft|lk=out|abbr=on|disp=or}})<ref name="Gewässerschutzkommission">Uta Mürle, Johannes Ortlepp, Peter Rey, Internationale Gewässerschutzkommission für den Bodensee (publ.): ''Der Bodensee: Zustand – Fakten – Perspektiven.'' 2nd revised edition. Bregenz, 2004, {{ISBN|3-902290-04-8}}, p.&nbsp;10.</ref> after Lake Geneva ({{convert|89|km3|cumi acre.ft|abbr=on|disp=or}}) and extends for over {{convert|69.2|km|mi}} between [[Bregenz]] and [[Stein am Rhein]]. Its [[drainage basin|catchment area]] is around {{convert|11500|km2|sqmi|abbr=on}}, and reaching as far south as [[Lago di Lei]] in Italy.<ref>[http://www.hydra-institute.com/igkb/IGKB%201.2.pdf www.hydra-institute.com] {{webarchive|url=https://web.archive.org/web/20120514054950/http://www.hydra-institute.com/igkb/IGKB%201.2.pdf |date=2012-05-14 }} (pdf; 1.2&nbsp;MB)</ref>

The area of the [[Obersee (Lake Constance)|Obersee]], or Upper Lake, is {{convert|473|km2|sqmi|abbr=on}}. It extends from Bregenz to [[Bodman-Ludwigshafen]] for over {{convert|63.3|km|mi}} and is {{convert|14|km|mi}} wide between [[Friedrichshafen]] and [[Romanshorn]]. At its deepest point between [[Fischbach (Friedrichshafen)|Fischbach]] and [[Uttwil]], it is {{convert|251.14|m|ft}} deep.

[[File:Bodensee vom Pfänder (Aurtia).JPG|thumb|Lake Constance with the Island of Lindau seen from the [[Pfänder]] in 2007]]
The three small bays on the [[Vorarlberg]] shore have their own names: the Bay of Bregenz, off [[Hard, Austria|Hard]] and [[Fußach]] 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 in [[Swiss Standard German]]), or [[Lake 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 (the ''Hörnle'', which belongs to the town of Konstanz) and Meersburg. The [[Constance Hopper]] lies between the German and Swiss shores east of [[Konstanz]].

The Obersee and Untersee are connected by the [[Seerhein]].

The [[Untersee (Lake Constance)|Untersee]], or Lower Lake, which is separated from the Obersee and from its north-west arm, the Überlinger See, by the large peninsula of [[Bodanrück]], has an area of {{convert|63|km2|sqmi|abbr=on}}. It is strongly characterised and divided into different areas by [[end moraine]]s, various [[glacial snout]]s and [[medial moraine]]s. These various areas of the lake have their own names. North of [[Reichenau Island]] is the [[Gnadensee]]. West of the island of Reichenau, between the peninsula of [[Höri (Lake Constance)|Höri]] and the peninsula of [[Mettnau]] is the Zeller See (or Zellersee in Swiss Standard German), or [[Lake Zell]]. North of the peninsula and swamp land Mettnau lies the lake part Markelfinger Winkel. The [[drumlin]]s of the southern Bodanrück continue along the bed of these northern parts of the lake. South of the Reichenau, from [[Gottlieben]] to [[Eschenz]], stretches the ''Rheinsee'' (lit.: "Rhine Lake") with strong Rhine currents in places. Previously this lake part was named Lake Bernang after the village of [[Berlingen, Switzerland|Berlingen]]. On most of the maps the name of the ''Rheinsee'' is not shown, because this place is best suited for the name of the Untersee.<ref name="Seespiegel_20">[http://www.seespiegel.de/html/archiv/Artikel/Nummer20/1204_002.htm ''Der Bodensee: drei Teile, ein See.''] In: ''Seespiegel.'' Edition 20.</ref>

{{multiple image|perrow = 3|total_width=900
|align=center
|header = Lake Constance on the Swiss National Map (1:50'000)
|image1=206 Stein am Rhein.jpg
|image2=207 Konstanz.jpg
|image3=14000by9600white.svg<!--left blank-->
|image4=216 Frauenfeld.jpg
|image5=217 Arbon.jpg
|image6=218 Bregenz.jpg
|footer = 
}}

=== Emergence and future ===
The present-day shape of Lake Constance has resulted from the combination of several factors:
* The [[tectonic]] Lake Constance Basin between the Alps and the Jura was created in the [[Jurassic]] and [[Tertiary]] periods.
* The current [[Alpine Rhine]] was initially a tributary of the Danube.
* Over time, the basin was [[stream capture|captured]] by the [[High Rhine]] as a result of [[headward erosion]] ([[fluvial erosion]]).
** The capture was not always only along the present Rhine valley; [[Lake Überlingen]] marks part of an older valley course.
* The river valleys were deepened during several [[cold period]]s by the [[Rhine Glacier]] from the valley of the Alpine Rhine ([[glacial erosion]]).
* Behind the present impressive traces of the [[Würm Ice Age]], the effects of older cold periods can no longer be explored in any detail. Lake Constance now represents, above all, a [[zungenbecken]] or [[glacial lake]] of the Würm Glaciation.<ref>quaternary-science.publiss.net/articles/452/download Albert Schreiner: ''Zur Entstehung des Bodenseebeckens'' (Quaternary Science Journal, pdf)</ref>
* During a later phase of the ice age, only the Obersee was glaciated. As the glacier retreated further, the [[glacial meltwater]]s 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.<ref>[http://www.landeskunde-online.de/rhein/bodensee/geologie.htm Geology of Lake Constance] at landeskunde-online.de. Retrieved 31 August 2017.</ref> <!-- It is questionable whether there has ever been an undivided Lake Constance -->

Like any glacial lake, Lake Constance will also silt up by [[sedimentation]]. This process can best be observed at the mouths of the larger rivers, especially that of the Alpine Rhine. The [[silting up]] process is accelerated by ever-increasing erosion by the Rhine and the associated reduction in the level of the lake.

=== Tributaries ===
[[File:Aerial image of the mouth of the Rhine into Lake Constance.jpg|thumb|The mouth of the Alpine Rhine into Lake Constance]]
The main tributary of Lake Constance is the [[Alpine Rhine]]. The Alpine Rhine and the [[Seerhein]] do not mix greatly with the waters of the lake and flow through the lakes along courses that change relatively little. There are also numerous smaller tributaries (236 in all). The most important tributaries of the Obersee are (counterclockwise) the [[Dornbirner Ach]], [[Bregenzer Ach]], [[Leiblach]], [[Argen]], [[Schussen]], [[Rotach (Lake Constance)|Rotach]], [[Brunnisach]], [[Linzer Aach|Seefelder Aach]], [[Stockacher Aach]], [[Salmsacher Aach]], the [[Aach (Lake Constance, Arbon)|Aach near Arbon]], [[Steinach (Lake Constance)|Steinach]], [[Goldach (river)|Goldach]] and the [[Old Rhine (Fußach)|Old Rhine]]. The outflow of the Obersee is the [[Seerhein]], which in turn is the main tributary of the Untersee. The most important tributary of the Untersee is the [[Radolfzeller Aach]]. The source of the Radolfzeller Aach is the [[Aachtopf]], a [[karst spring]] whose waters mostly derive from the [[Danube Sinkhole]]. Therefore, the [[Danube]] is indirectly also a tributary of the Rhine.
{| class="wikitable sortable"
|+ The ten biggest tributaries of the Obersee by discharge volume<ref>Landesanstalt für Umwelt, Messungen und Naturschutz in Baden-Württemberg: [http://www.lubw.baden-wuerttemberg.de/servlet/is/8849/jhdt_hochwasser.pdf?command=downloadContent&filename=jhdt_hochwasser.pdf ''Informationen zum Jahrhunderthochwasser 1999.''] {{Webarchive|url=https://web.archive.org/web/20131023235412/http://www.lubw.baden-wuerttemberg.de/servlet/is/8849/jhdt_hochwasser.pdf?command=downloadContent&filename=jhdt_hochwasser.pdf |date=2013-10-23 }} (pdf; 24&nbsp;kB)</ref> with its catchment areas:<ref>Internationale Gewässerschutzkommission für den Bodensee (publ.): ''Der Bodensee. Zustand – Fakten – Perspektiven.'' IGKB, Bregenz, 2004, {{ISBN|3-902290-04-8}}, [http://www.hydra-institute.com/igkb/IGKB%201.2.pdf Kapitel 1.2] {{webarchive|url=https://web.archive.org/web/20120514054950/http://www.hydra-institute.com/igkb/IGKB%201.2.pdf |date=2012-05-14 }} (pdf; 1.2&nbsp;MB)</ref>
|-
! align="left"| River
! align="left"| Average discharge<br />[m<sup>3</sup>/s] (1978–1990)
! align="left"| Discharge<br />in %
! align="left"| [[Drainage divide|Catchment]]<br />[km<sup>2</sup>]
! align="left"| Catchment<br />in %
|-
|Alpine Rhine || align="right"| 233 || align="right"| 61.1 || align="right"| 6,119 || align="right" | 56.1
|-
|Bregenzer Ach || align="right"| 48 || align="right"| 12.6 || align="right" | 832 || align="right"| 7.6
|-
|Argen || align="right"| 19 || align="right"| 5.3 || align="right"| 656 || align="right"| 6.0
|-
|Old Rhine<br />(Rhine Valley Canal) || align="right"| 12 || align="right"| 3.1 || align="right"| 360 || align="right"| 3.3
|-
|Schussen || align="right"| 11 || align="right"| 2.9 || align="right" | 822 || align="right"| 7.5
|-
|Dornbirner Ach || align="right" | 7.0 || align="right"| 1.8 || align="right"| 196 || align="right"| 1.8
|-
|Leiblach || align="right"| 3.3 || align="right" | 0.9 || align="right"| 105 || align="right"| 1.0
|-
|Seefelder Aach || align="right"| 3.2 || align="right" | 0.8 || align="right"| 280 || align="right"| 2.6
|-
|Rotach || align="right"| 2.0 || align="right"| 0.5 || align="right"|130 || align="right"| 1.2
|-
|Stockacher Aach || align="right"| 1.6 || align="right"| 0.4 || align="right"| 221 || align="right"| 2.0
|- style="background:#EEEEEE;" class="sortbottom"
|''Sum of the<br />10 main tributaries'' || align="right" | ''340'' || align="right"| ''89.6'' || align="right"| ''9,721'' || align="right"| ''89.2''
|- style="background:#DDDDDD;" class="sortbottom"
|Total inflow || align="right"| 381 || align="right"| 100.0 || align="right" | 10,903 || align="right" | 100.0
|}<!-- <small>Empty cells mean there is no data in the publications.</small> -->

Because the Alpine Rhine brings with it [[drift (geology)|drift]] from the mountains and deposits this material as [[sedimentation|sediment]], 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.

=== Outflows, evaporation, water extraction ===
The outflow of the Untersee is the [[High Rhine]] with the [[Rhine Falls]] at [[Schaffhausen]]. Both the average precipitation of 0.45&nbsp;km<sup>3</sup>/a and evaporation which averages 0.29&nbsp;km<sup>3</sup>/a cause a net change in the level of Lake Constance that is less when compared to the influence of the inflows and outflows.<ref name="Gewässerschutzkommission"/> Further quantities of lake water are extracted by municipal waterworks around the lake and the water company of [[Bodensee-Wasserversorgung]].

=== Islands ===
{{Anchor|Island anchor}}
[[File:Insel Mainau im Bodensee.jpg|thumb|The island of Mainau]]
{{Main|List of islands in Lake Constance}}
In Lake Constance there are ten [[island]]s that are larger than {{cvt|2,000|m2}}.

By far the largest is the [[island of Reichenau]] in the Untersee, which belongs to the municipality of [[Reichenau (Konstanz)|Reichenau]]. The former [[Reichenau Abbey|abbey of Reichenau]] is a [[UNESCO]] [[World Heritage Site]] due to its three early and highly medieval churches. The island is also known for its intensive cultivation of [[fruit]] and [[vegetables]].

The island of [[Lindau (island)|Lindau]] 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 is [[Mainau]] in the southeast of Lake Überlingen. The owners, the family of [[House of Bernadotte|Bernadotte]], 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 the [[Wollmatinger Ried]]: the [[Triboldingerbohl]] which has an area of {{cvt|13|ha}} and Mittler or Langbohl which is just {{convert|3|ha|spell=in}} in area.

Smaller islands in the Obersee are:
* Dominican Island (''Dominikanerinsel'') separated by a six-metre-wide ditch from the old town of [[Konstanz|Constance]] which is home to the Steigenberger Hotel ({{convert|2|ha|spell=in|disp=sqbr}})
* The tiny island of [[Hoy (Lake Constance)|Hoy]] near Lindau
* The ten artificial islands on the Rhine Causeway on the Fußach side
* The little island by the port of [[Romanshorn]]
* The Wollschweininsel (officially ''Wulesaueninsle'') by the Seepark in [[Kreuzlingen]]

In the Untersee are:
* the islands of [[Werd (Lake Constance)|Werd]], [[Mittleres Werdli]] and [[Unteres Werdli]] which together form the [[Werd Islands]] group are located at the outflow of the Rhine from the Untersee at Stein am Rhein into the [[High Rhine]].
* The so-called [[Liebesinsel (Lake Constance)|Liebesinsel]] ("Love Island", {{cvt|2,620|m2|disp=sqbr}}, southwest of the Mettnau peninsula.

=== Peninsulas ===
In Lake Constance there are several peninsulas which vary greatly in size:
* The [[Bodanrück]], the largest peninsula, separates the Überlinger See (Obersee) from the Untersee. It covers an area of {{cvt|112|km2}}.
* The [[Mettnau]] 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 {{cvt|1.7|km2}}.
* The [[Höri (Lake Constance)|Höri]], (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, the [[Rhine Delta (Lake Constance)|Rohrspitz]] juts out about {{cvt|1.2|km}} into the lake and forms the western perimeter of the Bay of Fußach. It has an area of about 50 hectares.
* The [[Wasserburg (Lake of Constance)|Wasserburg]] 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 {{cvt|2.3|ha}} and was an island until 1720, when the [[Fugger]]s built a causeway. In March 2009, 27 people lived on the peninsula.
* The [[Galgeninsel]] ("Gallows Island") in the Bay of Reutin is also a peninsula that was formerly an island. It is only 0.16 hectares in area.

=== Shore ===
[[File:BodenseeSandstrand03.jpg|thumb|Sandy shore at the [[Marienschlucht]]]]
The shores of Lake Constance consist mainly of gravel. In some places there are also sandy beaches, such as the [[Rohrspitz]] in the Austrian section of the lake, the [[Langenargen]] and [[Marienschlucht]].

According to the data of the International Water Protection Commission for the Lake Constance, the approximate shore length is {{cvt|273|km}} (see [[Coastline paradox]]). The inflow of water is constantly changing, mainly due to rain and the snow melt in the Alps. Its average surface area is about {{Höhe|395|DE-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).

=== Transportation ===
==== Road ====
Roads westbound [[Bundesstraße 33]] (B 33, highway), [[Bundesautobahn 81]] (A&nbsp;81), at Stockach, Konstanz: [[Bundesautobahn 98]] (A&nbsp;98), Switzerland: [[Autobahn 7 (Switzerland)|Autobahn 7]] (A7), [[Autobahn 1 (Switzerland)|Autobahn 1]] (A 1), [[Autobahn 23 (Switzerland)|Autobahn 23]] (A 23) and eastbound at Bregenz [[Rheintal/Walgau Autobahn]] (A&nbsp;14), at Lindau [[Bundesautobahn 96]] (A&nbsp;96), [[Bundesstraße 31]] (B&nbsp;31)

==== Ship / Ferry ====
{{main|:de:Bodenseehäfen}}
[[File:MS Karlsruhe in der Konstanzer Hafeneinfahrt.jpg|thumb|MS Karlsruhe arriving Constance]]
[[File:Schifffahrt Bodensee.png|thumb|right|Ship routes on Lake Constance and the High Rhine]]
There are eight main harbors offering boat services across the [[Obersee (Lake Constance)|Upper Lake]]:

;Austria:
* [[Bregenz]]

;Switzerland:
* [[Rorschach, Switzerland|Rorschach]]
* [[Romanshorn]]

;Germany:
* [[Lindau (Bodensee)|Lindau]]
* [[Friedrichshafen]]
* [[Meersburg]]
* [[Unteruhldingen]] (touristic harbor)
* [[Konstanz]]

<!--details:
* '''[[Konstanz]]''': 1839/41 Bau des nördlichen Hafens (13.000 m<sup>2</sup>) am „Konzilgebäude“; 1846/55 Bau der [[Werft]]; 1863 Anschluss an die Eisenbahn mit [[Bahnhof Konstanz|Bahnhof]] und zweiter, südlicher Hafen (55.000 m<sup>2</sup>) für Eisenbahntrajekte nach Lindau und Bregenz (bis 1917); 1890 Vereinigung der beiden Hafenteile. Seit 1993 ist die [[Imperia (Statue)|„Imperia“]] Wahrzeichen des Hafens. Ab 2005 Bau von [[Schwimmanleger]]n für den [[Katamaran Friedrichshafen–Konstanz|Katamaran]] und zwei Kursschiffe. Von Konstanz aus sind alle Verbindungen direkt möglich: Nach Schaffhausen, Überlingen, Bregenz und Rorschach. Die Werft wird nur noch als Werkstatt benutzt. Die Stadt ist Heimathafen der „badischen“ Schiffe, Sitz der BSB und der Stadtwerke Konstanz.

* '''[[Meersburg]]''': 1851/1852 Bau der steinernen [[Mole]]. Heute sind im Hafen zwei Schwimmanleger; ein weiterer Liegeplatz ist an der Außenmole. Kleiner aber wichtiger Umsteigehafen zum [[Überlinger See]] mit der Insel [[Mainau]]. Bis 1974 war der Meersburger Hafen offiziell ein DB-Bahnhof, der einzige in Deutschland ohne Gleisanschluss.
[[Datei:Lindau Hafen Luftbild.jpg|mini|Auf diesem Luftbild ist die Anbindung des Hafens an die Eisenbahn in Lindau gut erkennbar.]]

* '''[[Friedrichshafen]]''': 1811 Bau des „Stadthafens“, später für Dampfschiffe; 1846 Ausbau, 1851 Erweiterung (zum Teil mit Pfahlreihen) und Werft; 1854 Eisenbahnanschluss und erster [[Hafenbahnhof]]; 1869 Eisenbahntrajekt nach Romanshorn (bis 1976), ab 1929 auch für Kraftfahrzeuge; 1933 heutiges [[Bahnhof Friedrichshafen Hafen|Hafenbahnhofsgebäude]]; 1944 schwere Zerstörungen durch [[Bodenseeschifffahrt im Zweiten Weltkrieg|Luftangriffe]]; 2005 Bau eines Katamarananlegers; Liegeplatz für Boote der [[Wasserschutzpolizei]], des [[Kontrolleinheit See|Zolls]] und der [[Löschboot|Feuerwehr]]. Bis 1976 wurden Eisenbahnwaggons und Lokomotiven verschifft. Die [[Bodensee-Schiffsbetriebe#Werft|Werft]] dient nur noch der Reparatur und Revision der Schiffe. Friedrichshafen ist der Heimathafen der „württembergischen“ Schiffe der BSB und ein bedeutender [[Verkehrsknotenpunkt]], nicht nur für die Schifffahrt vom westlichen und östlichen Obersee, der [[Fährlinie Friedrichshafen–Romanshorn|Autofähre]] nach Romanshorn und dem Katamaran nach Konstanz, sondern auch mit den Bahn- und Flugverbindungen sowie den Rundflügen mit dem [[Zeppelin NT]]. {{Hauptartikel|Bodensee-Trajekte}}

* '''[[Lindau (Bodensee)|Lindau]]''': Seit 1200 befestigte Hafenstadt; 1812 steinerne Hafenmole für fast 100 Segelschiffe; 1848 Schiffswerft (bis 1961); 1854 Eisenbahnanschluss des Hafens über den [[Lindauer Bodenseedamm]] zum Hauptbahnhof auf der Insel; 1856 Ausbau des Hafens mit [[Bayerischer Löwe|Löwen-Statue]] und [[Neuer Lindauer Leuchtturm|„Neuem Leuchtturm“]] an der Einfahrt; 1869 Trajektverbindung nach Romanshorn und Konstanz; Heimathafen der „bayerischen“ Schiffe der BSB.<ref>[http://buergerwiki.net/Lindauer_Hafen Informationen zum Hafen Lindau]</ref>
[[Datei:MS Austria 2.JPG|mini|Das 75-jährige österreichische Flaggschiff ''[[Austria (Schiff, 1939)|Austria]]'' im Hafen von Bregenz vor dem Pfänder.]]
* '''[[Bregenz]]''': 1842/46 Bau einer hölzernen Hafenanlage für sechs Dampfschiffe; 1850 Ersatz durch eine Steinmole; 1872 Eisenbahnanschluss; 1884 Gründung der österreichischen Bodenseeflotte mit Heimathafen Bregenz; ab 1881 Hafenerweiterung mit [[Trockendock]] (bis 1940) und Trajektverbindungen nach Romanshorn, Konstanz und Friedrichshafen (bis 1913/17).<ref>[http://www.hafen-bregenz.at/index.asp Informationen zum Hafen Bregenz]</ref> Der Hafen besteht seitdem aus einem „großen Molo“ als Wellenbrecher, einem mittleren „Personenmolo“ mit Hafengebäude und Liegeplätze für drei Schiffe im Einsatz sowie einem „Reservemolo“ für Schiffe außer Betrieb. Zwischen diesen beiden wurde 1977 ein eiserner Steg mit Tankstelle errichtet. Bei der Sanierung 1996 wurden Liegeplätze für Privatboote geschaffen.<ref>''Über 100 Jahre Österreichische Bodenseeschifffahrt 1884–1984. Heimatkundliche Unterrichtsbildreihe.'' Herausgeber: Amt der Vorarlberger Landesregierung Schulmediencenter, Bregenz 1984/2003.[http://www.vobs.at/fileadmin/user_upload/smc/Bildreihen/Begleittexte/3500085_Bodenseeschifffahrt_Text.pdf] (PDF)</ref>

* '''[[Rorschach, Switzerland|Rorschach]]''': 1840 neue Hafenmole für den immer noch zu kleinen Hafen, deshalb 1862 Erweiterung zur heutigen Größe; 1856 unmittelbarer Eisenbahnanschluss; Heimathafen der drei kleinen [[Schweizerische Bodenseeschiffahrtsgesellschaft|SBS-Schiffe]] des ehemaligen [[Schifffahrtsbetrieb Rorschach|Schifffahrtsbetriebs Rorschach]].<ref>[http://www.bodensee-schiffe.ch/unterwegs/haefen/rorschach1.html Hafenplan Rorschach]</ref>

* '''[[Romanshorn]]''': Aus dem kleinen Hafen (1844) des Fischerdorfes entstand bis 1870 der flächenmäßig größte Bodenseehafen mit Gleisanschluss (1855) und Bahnhof direkt am Hafen und Trajektverbindungen nach Deutschland. Als Verkehrsknotenpunkt wurde der Heimathafen der vier großen SBS-Schiffe so bedeutsam, dass sich der Ort um den Hafen entwickelte. Die Trajekte wurden durch die Autofährlinie Friedrichshafen-Romanshorn abgelöst. Die leistungsfähige Werft ist heute die einzige dieser Art am Bodensee.<ref>[http://bodensee-schiffe.ch/unterwegs/haefen/hafenromanshorn.html Hafenplan Romanshorn]</ref> {{Hauptartikel|Fährlinie Friedrichshafen–Romanshorn}}

* '''[[Unteruhldingen]]''': Der Ausflugs- und ehemalige Fährhafen befindet sich zwischen der Marina und dem ehemaligen Bahnhof. Die [[Bodensee-Schiffsbetriebe]] bieten Verbindungen nach Konstanz, Mainau, Überlingen, Meersburg, Daisendorf und Rorschach an.<ref>{{Internetquelle |url=https://www.bsb.de/de/bodensee-erlebnisse/rundfahrten/uhldingen |titel=Rundfahrten ab Unteruhldingen |hrsg=Bodensee-Schiffsbetriebe |abruf=2021-06-06}}</ref>-->

Additionally, [[ferry|car ferries]] link Romanshorn to Friedrichshafen, and Konstanz to Meersburg.<ref name=map500/><ref name=mapGPBW1/> Between 1869 and 1976, there used to be [[Lake Constance train ferries|train ferries]] across the lake.

Several smaller harbors on the Upper Lake offer boat trips along the German or Swiss coast (with one continuing over the [[Alter Rhein|Old Rhine]] to [[Rheineck]]).

The harbour in Konstanz is also served by the ''[[Schweizerische Schifffahrtsgesellschaft Untersee und Rhein]]'' (URh), which operates via the ''[[Seerhein]]'', [[Untersee (Lake Constance)|Lower Lake]] and [[High Rhine]] to [[Schaffhausen]].<ref>{{Cite web |url=https://www.urh.ch/en/ |title=''URh'' website |access-date=2024-06-24}}</ref> It docks at the harbours of [[Kreuzlingen]], Konstanz, [[Gottlieben]], [[Ermatingen]], [[Reichenau Island|Reichenau]], [[Mannenbach]], [[Berlingen, Switzerland|Berlingen]], [[Gaienhofen]], [[Steckborn]], [[Hemmenhofen]], Wangen, [[Mammern]], [[Öhningen]], [[Stein am Rhein]], [[Diessenhofen]], [[Büsingen am Hochrhein|Büsingen]] and Schaffhausen. [[Radolfzell]] and [[Iznang]] are also linked by a boat line over the Lower Lake (to Konstanz).

====Rail====
{{Main|Lake Constance Belt Railway||Bodensee S-Bahn}}
[[File:Bregenz asv2022-10 img32 Zug der S1 am Bodensee.jpg|thumb|right|[[Vorarlberg S-Bahn]] (S1) trainset on the [[Vorarlberg Railway]] line]]
A network of several [[railway line]]s surrounds the lake. The lines are operated by regional train services ([[S-Bahn]], [[RegioExpress]], [[Regional-Express]]) spreading over four countries ([[Austria]], [[Germany]], [[Liechtenstein]], [[Switzerland]]).<ref>{{cite web |title=FahrplanNetzkarte 2024 |lang=de |url=https://www.thurbo.ch/fileadmin/user_upload/PDF/2024_Liniennetzplan_Zuerich_Ostschweiz_Bodensee.pdf |date=2023-12-10 |access-date=2023-12-18 |publisher=THURBO}}</ref> In Switzerland, they belong to [[S-Bahn St. Gallen]] and trains are operated by [[THURBO]] ([[Swiss Federal Railways]], SBB), [[Südostbahn]] (SOB) and [[Appenzell Railways]] (AB).<ref>{{cite web |title=''Fahrplan-Netzkarte 2024'' [Railway network and services near Lake Constance 2024] |lang=de |url=https://www.thurbo.ch/fileadmin/user_upload/PDF/2024_Liniennetzplan_Zuerich_Ostschweiz_Bodensee.pdf |date=2023-12-10 |access-date=2023-12-18 |publisher=THURBO}}</ref> The so-called [[Lake Constance Belt Railway|belt railway]] ({{lang|de|Bodensee-Gürtelbahn}}) along the northern shore is operated by [[DB Regio]] and [[SBB GmbH]]. In Austria and Liechtenstein, train services are operated by [[Austrian Federal Railways]] (ÖBB) for the [[Vorarlberg S-Bahn]]. Regional train services around Lake Constance are marketed as [[Bodensee S-Bahn]].

[[Railway station]]s close to harbours are, among others: {{rws|Bregenz Hafen}}, {{rws|Friedrichshafen Hafen}}, {{stn|Konstanz}}, {{rws|Kreuzlingen Hafen}}, {{stn|Lindau-Insel}}, {{stn|Radolfzell}}, {{rws|Romanshorn}} and {{rws|Rorschach Hafen}}.

Long-distance trains ([[Railjet|RJ/RJX]], [[EuroCity|EC/ECE]], [[Intercity (Deutsche Bahn)|IC (DB)]]/[[InterCity (Switzerland)|IC (SBB)]], [[InterRegio|IR]], [[Interregio-Express|IRE]]) link larger lakeside railway stations (e.g., {{rws|Bregenz}}, {{rws|Friedrichshafen Stadt}}, {{stn|Konstanz}}, {{stn|Lindau-Reutin}}, {{rws|Romanshorn}}) with major cities.

====Air====
Two [[airport]]s are located near the lake's shores: [[Friedrichshafen Airport]] (Germany) and [[St. Gallen–Altenrhein Airport]] (Switzerland). [[Zeppelin NT]] offers touristic [[zeppelin]] flights around Lake Constance departing from Friedrichshafen Airport.<ref>{{cite web |url=https://zeppelinflug.de/en/zeppelin-flights/overview?_gl=1*1l0443c*_up*MQ..&gclid=CjwKCAjw59q2BhBOEiwAKc0ijbqc72wwLctPsSo5TtMD1eivL9Njvt9B0cjOVffuEvhcLQYvvIseyhoCpZsQAvD_BwE |title=Overview of zeppelin flights in Germany |publisher=zeppelinflug.de |access-date=2024-09-04}}</ref>

=== Climate ===
[[File:Bodenseesturm.jpg|thumb|Summer storm – view of the [[Luitpoldkaserne (Lindau)|Luitpold Barracks]] in Lindau]]
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 a [[subtropical]] 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.

The [[Föhn]], a warm wind from the [[Mediterranean 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 of [[tropical 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 the [[heat 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. 
 
[[File:Foehnwind am bodensee.jpg|thumb|left|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 the [[Alpine 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. For [[storm 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 when [[squall]]s are expected of between 25 and 33&nbsp;[[knot (unit)|knots]] or registering [[wind speed|force]] 6 to 8 on the [[Beaufort scale]]. A [[gale 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 a ''Sturmballon'' ("storm ball") up the mast.

==== Freeze over ====
[[File:BodenseeGefroren.jpg|thumb|right|Frozen lake surface: skating in the [[Markelfinger Winkel]]]]
[[File:Seegfrörni 1963.jpg|thumb|right|Freezing 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-called ''Seegfrörne'' ([[Alemannic German|Alemannic]]) event was in 1963. The following is a list of [[Anno Domini|years]] in which Lake Constance froze over partially or completely:<ref>{{cite book |last=Meichle |first=Friedrich |chapter=Seegfrörne und Eisprozession in Vergangenheit und Gegenwart |title=Schriften des Vereins zur Geschichte des Bodensees und seiner Umgebung |volume=81 |year=1963 |pages=145–170 |issn=0342-2070 |language=de}}</ref><ref>{{cite book |last=Dobras |first=Werner |title=Seegfrörne: die spannende Geschichte der Seegfrörnen von 875 bis heute. 2. veränderte Auflage |publisher=Stadler |location=Konstanz |year=1992 |isbn=3-7977-0266-3 |language=de}}</ref>

*875, 895
*1074, 1076
*1108
*1217, 1227, 1277
*1323, 1325, 1378, 1379, 1383
*1409, 1431, 1435 (complete), 1460, 1465, 1470, 1479
*1512, 1517, 1553, 1560 (complete), 1564, 1565, 1571, 1573 (complete)
*1684, 1695 (complete)
*1788, 1796 (complete)
*1830 (complete), 1880 (complete)
*1929, 1963 (complete)

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-called [[Markelfinger Winkel]] between the municipality of [[Markelfingen]] and the [[Mettnau]] peninsula.

==== Floods ====
* A [[100-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 {{cvt|70|cm}} 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 {{cvt|68|cm}} above normal level.

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[[File:Panorama Hochwasser im Rheinholz.jpg|center|600px|thumb|Flooding on the shore of Lake Constance, May 2013]]

=== International borders ===
[[File:Lac de constance.jpg|thumb|Lake Constance, seen from a vineyard]]
The lake lies where the countries of Austria, Germany, and Switzerland meet.<ref name="Kramsch">{{cite book |last=Kramsch |first=Olivier Thomas |editor1-last=Brunet-Jailly |editor1-first=E. |title=Border Disputes: A Global Encyclopedia, Volume 2 |date=2015 |publisher=ABC-CLIO |isbn=978-1-61-069024-9 |page=453 |chapter-url=https://books.google.com/books?id=k9g5CgAAQBAJ&q=%22lake+constance%22 |chapter=Austria-Germany-Switzerland: Lake Constance (Konstanz)}}</ref> Beyond areas less than {{cvt|25|m}} 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.{{r|Kramsch}}<ref name="Kahn 2004">{{cite book |url=https://books.google.com/books?id=V01T5VI4nZ4C&pg=PA233 |title=Die deutschen Staatsgrenzen: rechtshistorische Grundlagen und offene Rechtsfragen ("The German national borders: legal-historical foundations and open legal questions") |author=Kahn, Daniel-Erasmus |publisher=Oxford University Press |year=2004 |isbn=978-3-16-148403-2}}</ref> 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 (international law)|condominium]]", and Germany holds an ambiguous opinion.{{r|Kramsch}}<ref>Jennings, Ken (16 June 2014) [http://www.cntraveler.com/stories/2014-06-16/lake-constance-maphead "The Borderless Black Hole in the Middle of Europe"] ''[[Conde Nast Traveler]]''</ref> Legal questions pertaining to ship transport and fishing are regulated in separate treaties.

Disputes occasionally arise. One concerns a [[houseboat]] which was moored in two states ([[European Court of Justice|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.<ref>Mark, David and Smith, Barry, et al., [http://ontology.buffalo.edu/smith//baarle/bizarre_shapes.htm "Bizarre Shapes: 100 Geographic Monsters"]</ref>