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Surprise flood kills salmon in West Iceland

21.08.2020 - 13:56
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 Mynd: RÚV - Elsa María Guðlaugs Drífudót
A jökulhlaup flood struck West Iceland’s Hvítá river in the early hours of Tuesday morning when water from a lagoon by the Langjökull glacier suddenly broke a new path and flowed in a different direction. Thick glacial mud now coats the river banks, and much of Borgarfjörður fjord.

According to Met Office monitoring equipment, flow in Hvítá river went from 90 cubic metres per second to 260 in just 12 hours. Monitors show the flow peaked at around 02.00 Tuesday morning. The flood transported three to four million cubic metres of muddy glacial meltwater from the lagoon to the sea.

This jökulhlaup was not caused by geothermal heat melting ice under a glacier, as is often the case in Iceland, and occurred in an area not accustomed to such floods. 

Hvítá remains muddy and many dead salmon have been discovered—as far away as 15 metres from the usual riverbank.  

The river surface rose by over two metres during the flood and there was a real danger to roads and bridges, though no serious damage has been recorded. The layer of new mud, however, is tens-of-centimetres thick in places. 

The flood originated in a glacial lagoon by Langjökull which first formed in 2008 and has been growing ever since. The lagoon usually drains to the north, into Flosavatn, just south of Eiríksjökull. This week, the lagoon drained suddenly to the south, into Svartá river, which is a tributary of Hvítá, and on into Borgarfjörður. 

The flood is blamed on the melting of the glacier. “People have been expecting these sorts of floods from lagoons that are forming around the country’s glaciers. We know of examples from many places in Iceland where water flow has been changing course because of the glaciers retreating, or that lagoons have been forming or disappearing,” says the Met Office’s Tómas Jóhannesson. “This is one of a great many examples of that.” 

Tómas says time will tell whether the flood was a one-off. He says it is not unlikely that the flow of water out of the lagoon will “heal” and return to normal. If that happens, the water level could rise again and lead to a repeat flood in the future. “Some of these peripheral lagoons have that habit,” Tómas says. 

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