Skaftá

Skaftá
Aerial view of main branch of the Skaftá where it flows into the Atlantic
Location
CountryIceland
Physical characteristics
MouthAtlantic Ocean
 • coordinates
63°39′50″N 17°48′0″W / 63.66389°N 17.80000°W / 63.66389; -17.80000 (primary)
Length115 km (71 mi)
Discharge 
 • average122 m3/s (4,300 cu ft/s)[1]
Basin features
LandmarksKirkjubæjarklaustur
Tributaries 
 • leftGrjótá, Hellisá, Fjaðrá
 • rightÚtfall, Nyðri-Ófærá, Syðri-Ófærá

The Skaftá (Icelandic pronunciation: [ˈskaftˌauː] ⓘ) is a river in South Iceland. It is primarily glacial in origin and has had its course modified by volcanic activity; as a result of both, it often floods because of glacial melting.

Course

The river's primary source is two subglacial "cauldrons" beneath Skaftájökull, part of the Vatnajökull glacier in the interior of Iceland.[2][3] It also receives spring-fed water from Langisjór, a lake a short distance to the west from which a tributary called the Útfall runs into the Skaftá. Other tributaries include the North and South Ófaerá, the Grjótá, and the Hellisá.[4][5]

West of Skaftárdalur, a farm named for the river valley, the Skaftá runs over a lava field in many channels, which recombine into three for the remainder of its course to the Atlantic: the Eldvatn or Ása-Eldvatn combines with the River Kúðafljót; the Ásakvísl or Árkvísla flows under a sand-covered lava field and has been affected by road construction; the third, easternmost branch, which flows near Kirkjubæjarklaustur, retains the name Skaftá[5] but has extremely low water levels when temperatures are lowest.[4] Its total length is approximately 115 kilometres (71 mi).[5]

The river was bridged at Kirkjubæjarklaustur in 1903 and the Ása-Eldvatn was bridged soon after. Efforts to bank and bridge the Ásakvísl have led to undermining of the bridge works and to erosion of land formerly watered by it.[5]

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Subglacial drainage of Skaftá jökulhlaups

Jökulhlaups

Beginning on June 8, 1783, the multi-year eruption of the volcanic system including Grímsvötn and Þórðarhyrna (sometimes referred to in Icelandic as the Skaftáreldur, Skaftá Fires)[6] filled the river valley with lava, including a gorge thought to have been 200 metres (660 ft) deep,[7] diverting its flow into the multiple shallow channels that now characterize its course. As a result it is more susceptible to jökulhlaups (glacial outburst floods), which occur every one to two years.[2][3][4][5][8][9] The 2015 flood was unusually damaging,[8] the largest since records began.[10]

Jökulhlaups may originate from either or both the western ice cauldron (Icelandic: Skaftárketill Vestari) or eastern ice cauldron (Icelandic: Skaftárketill Eystri) and it may initially be difficult to assign a source with confidence.[11] The cauldrons are associated with the two subglacial lakes (Icelandic: Skaftárkatlar), separated by a ridge at least 50 m (160 ft) high with no direct contact between them at the glacier bed bottom.[12] Sampling of microfloria has suggested not only that the two Skaftá ice lakes are connected through an aquifer in the underlying permeable basalt, but that this connection extends to the 6 km (3.7 mi) more distant Grímsvötn cauldron which drains via a different watershed.[12]

The long term trend appears to be for the western cauldron to produce floods more frequently and for the eastern cauldron to produce the largest floods.[13]

Skaftá Jökulhlaups since 2000 (minor not shown, see Atladóttir 2013 for those between 1955 and 2000[14])
Year Source Maximum Flow Comment[a]
2025 Unknown 250 m3/s (8,800 cu ft/s) [11]
2023 Eastern 620 m3/s (22,000 cu ft/s) [13]
2021 Eastern 1,500 m3/s (53,000 cu ft/s) [13]
2021 Western 610 m3/s (22,000 cu ft/s) modest flood that preceded the significant Eastern Cauldron flood by a few days[13][16]
2018 Both 2,000 m3/s (71,000 cu ft/s) Large flood,[16] but little impact due to accurate warning technology apart from destroyed bridges.[17]
2015 Eastern 3,000 m3/s (110,000 cu ft/s) The October event was the largest flood on record with significant infrastructure impact.[13]
2012 Western 380 m3/s (13,000 cu ft/s) [14]
2011 Western 404 m3/s (14,300 cu ft/s) [14]
2010 Eastern 1,283 m3/s (45,300 cu ft/s) Large downstream area flooded Eldhraun to the sea.[14]
2010 Western 558 m3/s (19,700 cu ft/s) [14]
2008 Eastern 1,350 m3/s (48,000 cu ft/s) [14]
2008 Western 390 m3/s (14,000 cu ft/s) [14]
2006 Western 194 m3/s (6,900 cu ft/s) [14]
2006 Eastern 1,370 m3/s (48,000 cu ft/s) [14]
2005 Western 723 m3/s (25,500 cu ft/s) [14]
2003 Eastern 241 m3/s (8,500 cu ft/s) [14]
2003 Western 436 m3/s (15,400 cu ft/s) [14]
2002 Eastern 689 m3/s (24,300 cu ft/s) [14]
2002 Western 720 m3/s (25,000 cu ft/s) [14]
2000 Eastern 1,240 m3/s (44,000 cu ft/s) [14]
2000 Western 699 m3/s (24,700 cu ft/s) [14]

See also

References

  1. ^ "Skaftá". Visit Klaustur (in Icelandic). Kirkjubæjarklaustur. Retrieved 2018-12-04.
  2. ^ a b Bergur Einarsson; Tómas Jóhannesson; Thorsteinn Thorsteinsson; Eric Gaidos (July 2017). "Subglacial flood path development during a rapidly rising jökulhlaup from the western Skaftá cauldron, Vatnajökull, Iceland". Journal of Glaciology. 63 (240): 670–682. doi:10.1017/jog.2017.33 – via ResearchGate.
  3. ^ a b Morgan T. Jones; Iwona M. Gałeczka; Athanasios Gkritzalis-Papadopoulos; Martin R. Palmer; Matthew C. Mowlem; Kristín Vogfjörð; Þorsteinn Jónsson; Sigurður R. Gislason (2015). "Monitoring of jökulhlaups and element fluxes in proglacial Icelandic rivers using osmotic samplers" (PDF). Journal of Volcanology and Geothermal Research. 291: 112–24. doi:10.1016/j.jvolgeores.2014.12.018.
  4. ^ a b c "Skafta River". Nat.is. Nordic Adventure Travel. Retrieved 2018-12-04.
  5. ^ a b c d e "Skaftá". Katla Geopark (in Icelandic). Retrieved 2018-12-04.
  6. ^ Th. Thordarson; S. Self (May 1993). "The Laki (Skaftár Fires) and Grímsvötn eruptions in 1783–1785". Bulletin of Volcanology (abstract). 55 (4): 233–63. doi:10.1007/BF00624353.
  7. ^ "Vatnajökull National Park—Lakagigar". Klaustur.is. Kirkjubæjarklaustur. Retrieved 2018-12-04.
  8. ^ a b "Jökulhlaups". Lava Centre. Retrieved 2018-12-04.
  9. ^ Bergur Einarsson (September 2009). "Jökulhlaups in Skaftá: A study of a jökulhlaup from the Western Skaftá cauldron in the Vatnajökull ice cap, Iceland" (PDF). Icelandic Meteorological Office. ISSN 1670-8261.
  10. ^ Bjarni Pétur Jónsson (2015-10-02). "Mesta Skaftárhlaup síðan mælingar hófust" (in Icelandic). RÚV.
  11. ^ a b "Skaftá flood has begun". mbl.is. 8 December 2025.
  12. ^ a b Marteinsson, V.T.; Rúnarsson, A.; Stefánsson, A.; Thorsteinsson, T.; Jóhannesson, T.; Magnússon, S.H.; Reynisson, E.; Einarsson, B.; Wade, N.; Morrison, H.G.; Gaidos, E. (February 2013). "Microbial communities in the subglacial waters of the Vatnajökull ice cap, Iceland". The ISME Journal. 7 (2): 427–437. doi:10.1038/ismej.2012.97. PMC 3554413.
  13. ^ a b c d e "Flood in Skaftá". Icelandic Meteorological Office. 29 August 2023.
  14. ^ a b c d e f g h i j k l m n o p Atladóttir, Auður (April 2013). Handbók um Skaftá Viðbragðsáætlun (PDF). Reykjavík: Icelandic Meteorological Office. ISSN 1670-8261.
  15. ^ "Search:Múlakvísl & Mýrdalssandur". Icelandic Meteorological Office. Retrieved 15 June 2024.
  16. ^ a b "Flood in Skaftá". Icelandic Meteorological Office. 10 September 2021.
  17. ^ "The August glacial outburst - one of the larger jökulhlaups to have affected Skaftá in recent decades". Icelandic Meteorological Office. 13 September 2018.

Notes

  1. ^ Jökulhlaup criteria for significance is road closure but this is arguable as valuable property damage can be minimal, especially with current warning mechanisms.[15]
  • Media related to Skaftá at Wikimedia Commons
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