Skaftá
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| Skaftá | |
|---|---|
 Aerial view of main branch of the Skaftá where it flows into the Atlantic | |
 | |
| Location | |
| Country | Iceland |
| Physical characteristics | |
| Mouth | Atlantic Ocean |
• coordinates | 63°39′50″N 17°48′0″W / 63.66389°N 17.80000°W (primary) |
| Length | 115 km (71 mi) |
| Discharge | |
| • average | 122 m3/s (4,300 cu ft/s)[1] |
| Basin features | |
| Landmarks | Kirkjubæjarklaustur |
| Tributaries | |
| • left | Grjótá, Hellisá, Fjaðrá |
| • right | Útfall, 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.
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]
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]
| 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] |
