View source for Mälaren

{{Short description|Third largest lake in Sweden}}
{{Infobox body of water
| name               = Mälaren
| image              = Mälarsee.jpg
| caption            = Lake Mälaren at dusk
| alt                = View of Mälaren
| image_bathymetry   = 
| caption_bathymetry = 
| location           = [[Sweden]]
| coords             = {{coord|59|30|N|17|12|E|region:SE_type:waterbody_scale:1000000|display=inline,title}}
| pushpin_map        = Sweden
| pushpin_map_alt    = Location in Sweden
| type               = 
| inflow             = 
| outflow            = [[Norrström]]
| catchment          = 
| basin_countries    = [[Sweden]]
| length             = 
| width              = 
| area               = {{convert|1,140|km2|abbr=on}}
| depth              = {{convert|13|m|abbr=on}}
| max-depth          = {{convert|64|m|abbr=on}}
| volume             = {{convert|14|km3|acre.ft|abbr=on}}
| residence_time     = 
| shore              = 
| elevation          = {{convert|3|m|ft}}
| islands            = [[Selaön]], [[Svartsjölandet]] (''see [[#Larger islands|list]]'')
| cities             = 
}}

'''Mälaren''' ({{IPAc-en|UK|ˈ|m|ɛ|l|ər|ɛ|n}} {{respell|MEL|ər|en}}, {{IPAc-en|US|ˈ|m|eɪ|l|ɑːr|ə|n}} {{respell|MAY|lar|ən}},<ref>{{Cite American Heritage Dictionary|Mälaren|access-date=April 14, 2019}}</ref><ref>[https://web.archive.org/web/20190414110106/https://en.oxforddictionaries.com/definition/us/M%25C3%25A4laren "Mälaren"] (US) and {{Cite dictionary |url=http://www.lexico.com/definition/M%C3%A4laren |title=Mälaren |dictionary=[[Lexico|Oxford Dictionaries]] UK English Dictionary |publisher=[[Oxford University Press]] }}{{Dead link|date=September 2022 |bot=InternetArchiveBot |fix-attempted=yes }}{{dead link|date=September 2022|bot=medic}}{{cbignore|bot=medic}}</ref><ref>{{Cite Merriam-Webster|Mälaren|access-date=April 14, 2019}}</ref> {{IPA|sv|ˈmɛ̂ːlarɛn|lang|sv-Mälaren.ogg}} <small>or</small> {{IPA|sv|ˈmɛ̂ːlaɳ|}}),<ref>{{cite book|url=https://runeberg.org/ortnamn/0021.html|author1=Jöran Sahlgren|author2=Gösta Bergman|title=Svenska ortnamn med uttalsuppgifter|language=sv|year=1979|page=17|access-date=2023-12-26|archive-date=2021-01-28|archive-url=https://web.archive.org/web/20210128031255/https://runeberg.org/ortnamn/0021.html|url-status=live}}</ref> historically referred to as '''Lake Malar''' in English, is the third-largest freshwater lake in [[Sweden]] (after [[Vänern]] and [[Vättern]]). Its area is {{cvt|1,140|km2}} and its greatest depth is 64 m (210 ft). Mälaren spans {{cvt|120|km|1}} from east to west. The lake drains, from south-west to north-east, into the [[Baltic Sea]] through its natural outlets [[Norrström]] and [[Söderström (Stockholm)|Söderström]] (as it flows around [[Stadsholmen]] island) and through the artificial [[Södertälje Canal]] and [[Hammarbyleden]] waterway. The easternmost bay of Mälaren, in central [[Stockholm]], is called [[Riddarfjärden]]. The lake is located in [[Svealand]] and bounded by the provinces of [[Uppland]], [[Södermanland]] and [[Västmanland]]. The two largest islands in Mälaren are [[Selaön]] ({{cvt|91|km2|1}}) and [[Svartsjölandet]] ({{cvt|79|km2|1}}). Mälaren is low-lying and mostly relatively shallow.

Being a quite narrow and shallow lake, Mälaren has bridge crossings between [[Eskilstuna]] and [[Västerås]] with two crossings on the western end at [[Kvicksund]] and three separate bridges between [[Strängnäs]] and [[Enköping]] in the central part of the lake. On the eastern end, the entirety of [[Ekerö Municipality]] is set on islands within Mälaren. That urban area also has a bridge connection to the mainland in Stockholm along with bridges between various islands in the municipality.

The [[Viking Age]] settlements [[Birka]] on the island of [[Björkö (Ekerö)|Björkö]] and [[Hovgården]] on the neighbouring island [[Adelsö]] have been a [[UNESCO World Heritage Site]] since 1993, as has [[Drottningholm Palace]] on the island of [[Lovön]].
The barrow of [[Björn Ironside]] is on the island of Munsö, within the lake.
[[File:Beorn Ironside barrow 2009 (7).jpg|right|thumb|300px|The barrow of Björn Ironside (''Björn Järnsidas hög'') on the island of Munsö, in lake Mälaren, [[Sweden]]. The barrow is crowned by a stone containing the fragmented [[Uppland Runic Inscription 13]].]]

==Etymology==
The [[etymology|etymological]] origin of the name {{lang|sv|Mälaren}} stems from the [[Old Norse]] word {{lang|non|mælir}} appearing in historical records in the 1320s and meaning [[gravel]].<ref>"[http://www.ne.se/uppslagsverk/encyklopedi/l%C3%A5ng/m%C3%A4laren Mälaren] {{Webarchive|url=https://web.archive.org/web/20180619214255/https://www.ne.se/uppslagsverk/encyklopedi/l%C3%A5ng/m%C3%A4laren |date=2018-06-19 }}". Nationalencyklopedin. Accessed 4 November 2016.</ref> The lake was previously known as {{lang|non|Lǫgrinn}}, which is [[Old Norse]] for 'The Lake'.<ref>Grimes, Heilan Yvette. The Norse Myths. P.285, 286</ref>

==Geology==
{{See also|Central Swedish lowland}}
[[File:La3-demis-malaren.png|300px|thumb|Mälaren details, with [[Stockholm urban area]] to the right in pink.]]
By the end of the last ice age about 11,000 years ago, much of northern Europe and North America was covered by [[ice sheet]]s up to {{cvt|3|km|1}} thick. At the end of the ice age when the glaciers retreated, the removal of the weight from the depressed land led to a [[post-glacial rebound]]. Initially the rebound was rapid, proceeding at about {{cvt|7.5|cm|2}} per year. This phase lasted for about 2,000 years, and took place as the ice was being unloaded. Once deglaciation was complete, uplift slowed to about {{cvt|2.5|cm|1}} per year, and decreased exponentially after that. Today, typical uplift rates are of the order of {{cvt|1|cm|2}} per year or less, and studies suggest that rebound will continue for about another 10,000 years. The total uplift from the end of deglaciation can be up to {{cvt|400|m|0}}.{{Citation needed|date=March 2007}}

In the [[Viking Age]], Mälaren was still a bay of the [[Baltic Sea]],<ref>{{Cite web |url=http://samla.raa.se/xmlui/bitstream/handle/raa/2222/1974_121.pdf?sequence=1 |title=Landhöjning och bebyggelse i nordligaste Uppland |access-date=2017-10-09 |archive-date=2017-10-20 |archive-url=https://web.archive.org/web/20171020135733/http://samla.raa.se/xmlui/bitstream/handle/raa/2222/1974_121.pdf?sequence=1 |url-status=dead }}</ref><ref>''Friman, Helena'', ''Söderström, Göran''. (2008). Stockholm: en historia i kartor och bilder.</ref> and seagoing vessels could sail up it far into the interior of Sweden. [[Birka]] was conveniently near the trade routes through the [[Södertälje Canal]]. Due to the post-glacial rebound, Södertälje canal and the mouth of [[Riddarfjärden]] bay had become so shallow by about the year 1200 that ships had to unload their cargoes near the entrances, and progressively the bay became a lake.<ref>{{Cite web |url=http://arne.ljungdahl.info/malaren/MALAREN.PHP |title=Om Mälaren |access-date=2017-10-09 |archive-date=2022-03-28 |archive-url=https://web.archive.org/web/20220328124627/http://arne.ljungdahl.info/malaren/MALAREN.PHP |url-status=live }}</ref> The decline of Birka and the subsequent foundation of [[Stockholm]] at the choke point of Riddarfjärden were in part due to the post-glacial rebound changing the topography of the Mälaren basin. The lake's surface currently averages {{cvt|.7|m|ft|1}} above [[sea level]].

==Mythology==
According to [[Norse mythology]] as contained in the thirteenth-century Icelandic work ''[[Prose Edda]]'', the lake was created by the goddess [[Gefjon]] when she tricked [[Gylfi]], the Swedish king of [[Gylfaginning]]. Gylfi promised Gefjon as much land as four oxen could plough in a day and a night, but she used oxen from the land of the giants, and moreover uprooted the land and dragged it into the sea, where it became the island of [[Zealand]]. ''Snorra Edda'' says that "the inlets in the lake correspond to the headlands in Zealand";<ref>Anthony Faulkes (ed. and trans), ''Snorri Sturluson: Edda'' (London: Everyman, 1987), p. 7.</ref> since modern maps show this to be more true of Lake [[Vänern]], the myth has been suggested to have been originally about Vänern, not Mälaren.<ref>Heimir Pálsson, 'Tertium vero datur: A study of the text of DG 11 4to', p. 44 http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-126249 {{Webarchive|url=https://web.archive.org/web/20190911224451/http://uu.diva-portal.org/smash/record.jsf?pid=diva2:322558&dswid=-1629 |date=2019-09-11 }}.</ref>

==Geography==
A selection, in alphabetical order:
{|
! Major islands
! Major sections from west to east
! Major cities and municipalities bordering the lake
|-
| valign="top" |
* [[Adelsö]]
* [[Aspön]]
* [[Björkö, Ekerö|Björkö]]
* [[Ekerön]]
* [[Helgö]]
* [[Kungsholmen]] (Stockholm)
* [[Kurön]]
* [[Lilla Essingen]] (Stockholm)
* [[Lovön]]
* [[Munsön]]
* [[Ridön (Västmanland)]]
* [[Ridön (Södermanland)]]
* [[Selaön]]
* [[Stora Essingen]] (Stockholm)
* [[Svartsjölandet]]
* [[Tosterön]]
| valign="top" |
* [[Galten (basin)|Galten]]
* [[Blacken (basin)|Blacken]]
* [[Långtarmen]]
* [[Freden]]
* [[Västeråsfjärden]]
* [[Granfjärden]]
* [[Oknöfjärden]]
* [[Gripsholmsfjärden]]
* [[Prästfjärden]]
* [[Björkfjärden]]
* [[Ekoln]]
* [[Gorran (basin)|Gorran]] & [[Skarven]]
* [[Östra Mälaren]]
| valign="top" |
* [[Bålsta]]
* [[Köping, Sweden|Köping]]
* [[Kungsängen]]
* [[Kungsör]]
* [[Mariefred]]
* [[Stockholm]]
* [[Strängnäs]]
* [[Södertälje]]
* [[Torshälla]]
* [[Uppsala]]
* [[Västerås]]
|}

==Ecology==
The most common [[nest]]ing birds on the skerries of Mälaren are also the most common in the Baltic Sea. After a survey in 2005, the ten most common species were found to be [[common tern]], [[European herring gull|herring gull]], [[black-headed gull]], [[common gull]], [[mallard]], [[tufted duck]], [[Canada goose]], [[common goldeneye]], [[lesser black-backed gull]] and [[common sandpiper]]. [[White-tailed eagle]], [[greylag goose]], [[barnacle goose]], [[black-throated diver]], [[red-breasted merganser]] and [[gadwall]] are less common, and some of these latter are endangered in the Mälaren area. Since 1994 a subspecies of [[great cormorant]] ''Phalacrocorax carbo sinensis'', has nested there as well. A 2005 survey tallied 23 breeding colonies with 2178 nests, of which the largest colony had 235 nests. Most experts believe the great cormorant population has peaked and will stabilize at around 2000 nests.<ref name="fåglar">[http://www.skargardsbryggan.com/dokument/malarens_faglar_2005_.pdf Länsstyrelsen i Stockholms län] {{webarchive|url=https://web.archive.org/web/20070928042245/http://www.skargardsbryggan.com/dokument/malarens_faglar_2005_.pdf |date=2007-09-28 }} - Rapport 2006:02: Mälarens Fåglar (pdf, in Swedish)</ref>

One of the characteristic species is the [[osprey]] which has one of its strongest presences in Lake Mälaren. The osprey nests in almost all bays of the lake.<ref name="fåglar"/>

The [[Zebra mussel]] is considered an [[invasive species]] and is causing some problems in Lake Mälaren.

Lake Mälaren has 33 species of naturally occurring fish species, which makes it Sweden’s most diverse lake in regard to fish. Other species have been introduced to the environment, including the common carp and the rainbow trout. The rainbow trout in particular is known to compete with indigenous fish for habitat and food, as they have a faster growth rate and predate on local species. However, they are not considered to have made a significant impact.<ref name=":0">{{Cite journal |last1=Josefsson |first1=M. |last2=Andersson |first2=B. |date=December 2001 |title=The environmental consequences of alien species in the Swedish lakes Mälaren, Hjälmaren, Vänern and Vättern |url=https://pubmed.ncbi.nlm.nih.gov/11878025/ |journal=Ambio |volume=30 |issue=8 |pages=514–521 |doi=10.1579/0044-7447-30.8.514 |issn=0044-7447 |pmid=11878025 |s2cid=2171081 |access-date=2022-10-13 |archive-date=2022-10-13 |archive-url=https://web.archive.org/web/20221013114431/https://pubmed.ncbi.nlm.nih.gov/11878025/ |url-status=live }}</ref>

=== Crayfish ===
Crayfish are of large cultural and economic importance in Sweden, with [[Crayfish party|crayfish parties]] being a longtime annual tradition for many Swedes.

Lake Mälaren was the first lake in Sweden to be affected by the [[crayfish plague]] (''A. astaci'' Schicora'')'' when infected crayfish imported from Finland were introduced to the lake with the intention of human consumption. The plague spread quickly through the lake, exacerbated by boat traffic, which decimated the indigenous [[Astacus astacus|noble crayfish]] (''A. astacus'') population and caused severe economic losses to the local fishing industry. From Mälaren, the plague spread rapidly to all freshwater bodies in Sweden.

After multiple recurrent outbreaks and failed attempts to restore populations of the noble crayfish, Swedish authorities introduced the North American [[signal crayfish]] (''P. leniusculus)'' to L. Mälaren, a species that is resistant to the plague. Since 1969, Mälaren has been continuously stocked with signal crayfish.<ref name=":0" /> However, it was later discovered that signal crayfish were often carriers of crayfish plague. In addition, while populations of noble crayfish and signal crayfish have been known coexist, their larger size, faster growth rate, and aggressiveness often allows them to dominate populations of noble crayfish. This, in addition to habitat degradation,<ref>{{Cite journal |last1=Capinha |first1=César |last2=Larson |first2=Eric R. |last3=Tricarico |first3=Elena |last4=Olden |first4=Julian D. |last5=Gherardi |first5=Francesca |date=August 2013 |title=Effects of climate change, invasive species, and disease on the distribution of native European crayfishes |url=https://pubmed.ncbi.nlm.nih.gov/23531056 |journal=Conservation Biology |volume=27 |issue=4 |pages=731–740 |doi=10.1111/cobi.12043 |issn=1523-1739 |pmid=23531056 |s2cid=25775481 |access-date=2022-10-13 |archive-date=2022-10-13 |archive-url=https://web.archive.org/web/20221013231552/https://pubmed.ncbi.nlm.nih.gov/23531056/ |url-status=live }}</ref> has led to a significant decrease in noble crayfish populations in L. Mälaren.

Signal crayfish have been largely successful in Sweden and rapidly expanded as a replacement population to noble crayfish. Stocking this species is now prohibited within multiple lakes in Sweden in order to protect noble crayfish population. In the Stockholm municipality, which includes L. Mälaren, signal crayfish are now illegal to import, move, or farm.<ref>{{Cite web |title=Kräftfiske - Stockholms stad |url=https://parker.stockholm/fiske/kraftfiske/ |access-date=2022-10-13 |website=parker.stockholm |language=sv |archive-date=2022-10-13 |archive-url=https://web.archive.org/web/20221013114441/https://parker.stockholm/fiske/kraftfiske/ |url-status=dead }}</ref> There have been efforts to encourage farming of noble crayfish populations instead.<ref>{{Cite web |title=Noble Crayfish farming in Sweden |url=https://www.slu.se/en/Collaborative-Centres-and-Projects/slu-aquaculture/education/noble-crayfish-farming-in-sweden/ |access-date=2022-10-13 |website=SLU.SE |language=en |archive-date=2022-10-13 |archive-url=https://web.archive.org/web/20221013114433/https://www.slu.se/en/Collaborative-Centres-and-Projects/slu-aquaculture/education/noble-crayfish-farming-in-sweden/ |url-status=live }}</ref> However, illegal farming of signal crayfish continues to be a problem due to greater public demand for the larger signal crayfish.<ref>{{Cite journal |last1=Bohman |first1=P. |last2=Degerman |first2=E. |last3=Edsman |first3=L. |last4=Sers |first4=B. |date=2011 |title=Exponential increase of signal crayfish in running waters in Sweden – due to illegal introductions? |url=https://www.kmae-journal.org/articles/kmae/abs/2011/02/kmae110017/kmae110017.html |journal=Knowledge and Management of Aquatic Ecosystems |language=en |issue=401 |pages=23 |doi=10.1051/kmae/2011040 |issn=1961-9502 |doi-access=free |access-date=2022-10-13 |archive-date=2022-10-13 |archive-url=https://web.archive.org/web/20221013114431/https://www.kmae-journal.org/articles/kmae/abs/2011/02/kmae110017/kmae110017.html |url-status=live }}</ref>

== Mapping ==
From the mid 17th century onwards, multiple expeditions to measure and map L. Mälaren were undertaken. The lake was strategically and economically important, and there was a lack of a reliable map to navigate it. However, L. Mälaren’s many islands and bays made it an extensive and laborious task to measure.

In 1687, [[Charles XI of Sweden|King Charles XI of Sweden]] commissioned cartographer [[Carl Gripenhielm]] to map Lake Mälaren and its surrounding provinces.<ref>{{Cite book |last=Landell |first=Nils-Erik |url=https://www.worldcat.org/oclc/165391840 |title=Stockholmskartor |date=1992 |publisher=Rabén & Sjögren |isbn=91-29-61681-6 |location=[Stockholm] |oclc=165391840}}</ref> From 2 August 1688 to 17 September 1688 Gripenhielm conducted the bulk of his expedition, and he would complete the map in 1689, known in Swedish as [[Gripenhielm's Mälarkarta|Gripenhielm's ''Mälarkarta'']]. The Mälarkarta is unique in that it is surrounded by a frame of 96 small, realistic gouache paintings of cities, castles, mansions, and fairways around Lake Mälaren. The map is hand drawn on regal paper, and measures {{cvt|3.46 x 2.14|m}}. It has been kept in the [[National Library of Sweden]] since 1884. Due to its larger size, it was initially hung in the large viewing room, however in 1931 it was moved to a more secluded wall in a corridor to the map department. Heavy handed preservation techniques have led to some degradation on the illustrations. Since 1961, the map hangs in an area that the public does not have access to.

Gripenheim’s Mälarkarta was valid until 1739 when a new, more accurate map of L. Mälaren was completed by the then surveyor and cartographer [[Jacob Nordencreutz]].

==Trivia==
* ''Mälardrottningen'' (Lake Mälar Queen) is a poetic name for [[Stockholm]] well known in Swedish literature.
* [[Utter Inn]], an underwater [[hotel]] designed by the artist [[Mikael Genberg]], is in the lake.
* The area around the lake hosted the [[Cycling at the 1912 Summer Olympics|cycling]] events at the [[1912 Summer Olympics]].<ref>[http://www.la84foundation.org/6oic/OfficialReports/1912/1912.pdf 1912 Summer Olympics official report.] {{Webarchive|url=https://web.archive.org/web/20080410231505/http://www.la84foundation.org/6oic/OfficialReports/1912/1912.pdf |date=2008-04-10 }} p. 224.</ref>

==See also==
* [[Mälaren Valley]] ''(Mälardalen)''
* [[List of lakes of Sweden]]
* [[Geography of Stockholm]]
* [[Almarestäket]]
* [[Kanaanbadet]]

==References==
{{Reflist}}

==External links==
{{Commons category}}
{{AmCyc Poster|Mælar}}
*[https://web.archive.org/web/20010519193058/http://www.malaren.com/ Mälarguiden] - Guide to Mälaren (mostly in Swedish but a lot of maps and some English text)
*[http://www.malarslott.se/ Castles around Mälaren] {{Webarchive|url=https://web.archive.org/web/20070530040432/http://www.malarslott.se/ |date=2007-05-30 }}

{{Large lakes of Sweden}}
{{1912 Summer Olympic venues}}
{{Olympic venues cycling}}
{{Authority control}}

{{DEFAULTSORT:Malaren}}
[[Category:Mälaren| ]]
[[Category:Norrström basin]]
[[Category:Venues of the 1912 Summer Olympics]]
[[Category:Olympic cycling venues]]
[[Category:Lakes of Södermanland County]]
[[Category:Lakes of Stockholm County]]
[[Category:Landforms of Uppsala County]]
[[Category:Landforms of Västmanland County]]