Iceland encyclopedia Hot Spring

Deildartunguhver

Deildartunguhver is a high-discharge geothermal spring in Borgarfjörður, West Iceland. It combines a conspicuous natural hot-water source with a major role in district heating and a remarkably specialised plant habitat.

Illustration
An illustrated impression of Iceland

Overview

About Deildartunguhver

A powerful natural water source

A 2023 government report describes a flow of about 180 litres per second at temperatures of 97–99 degrees Celsius. Deildartunguhver forms part of the wider Reykholtsdalur geothermal system. Its importance lies in the volume of water emerging naturally at the surface as well as the water's high temperature.

Heat carried to communities

The Akranes and Borgarfjörður heating utility was established in 1979. Hot water from Deildartunguhver travels through a long pipeline serving communities far from the spring. The 2023 report states that water takes two to three days to reach Akranes and cools by a little over ten degrees on the journey, illustrating the practical scale of geothermal heat distribution.

An exceptional fern habitat

The fern tunguskollakambur, Struthiopteris fallax, grows beside the spring. In its 2022 annual report, the Icelandic Institute of Natural History identified Deildartunguhver as its only known locality. Research examined the fern's genetics, soil and habitat requirements, making this small patch of geothermal vegetation important for conservation.

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