Fresh Waters on the Faroe Islands

The Faroese climate is characterised by considerable precipitation and, on average, it rains or snows for more than 270 days per year. For example, Tórshavn gets more than 1,200 mm of rain per year, while average rainfall in Hvalvík a little further north is as much as 3,200 mm per year. Remote areas such as Mykines and Akraberg are drier and get less than 900 mm of rain per year. It is these vast volumes of water that form the basis for the Faroe Islands’ many fresh waters.

Until recently, it was generally believed that there was no groundwater in the Faroe Islands, and that all rainfall ran over the rocks as surface water and into the lakes, streams and sea. However, the islands do have groundwater which can be revealed by springs that do not dry out in periods without rainfall. In addition, it is assumed that hot springs such as Varmakelda at Kambsdalur are connected to deep groundwater. Groundwater deposits also show as inflowing water in several tunnels, just as they can appear in boreholes in connection with the installation of e.g. geothermal heating.

Despite the presence of groundwater, a very significant part of the rainfall runs into lakes and streams as surface water, and the effect is usually very evident. During periods of rain, the water level and speed in the streams increase rapidly, while the opposite happens at almost the same speed when the weather is dry. Several days without rain can cause small lakes to dry out, and if there is no rain for weeks, many of even the slightly larger lakes dry out, while the streams shrink into smaller brooks.

Ecological status of lakes and streams

The amount of phosphorus in the Faroese subsoil is small, and due to the low concentration of dissolved phosphorus, the lakes and streams are predominantly low in nutrients. However, an increased supply of nutrients from agriculture, fish farming and settlements has had an impact on certain lakes and streams. This can lead to increased algae growth, which reduces water transparency and inhibits the spread of aquatic plants, and can ultimately also have a negative effect on wildlife. However, the nutrient load can also come from more natural sources. For example, black-legged kittiwakes often congregate at certain lakes, where their nutrient-rich droppings can lead to nutrient loading of the water.

Fresh water plant and wildlife

Plant life in Faroese fresh waters is relatively modest. Fens are dominated by common cotton sedge (Eriophorum angustifolium), dioecious sedge (Carex dioica) and common black sedge (Carex nigra) and a number of different peat mosses (Sphagnum spp.). Another common Faroese moss is the bright green fountain-apple moss (Philonotis fontana). It mainly occurs in springs, where it often grows together with starry saxifrage (saxifraga stellaris).

The Faroese streams are often so steeply sloped and have such a strong current that the plants have difficulty taking root. However, it is possible to find greater water-moss (Fontinalis antipyretica) in most streams, while smaller brooks, where the current is not so strong, can also feature species such as bog pondweed (Potamogeton polygonifolius) and alternateflower watermilfoil (Myriophyllum alterniflorum).

As you move up to the bank, plant life becomes much more diverse. This is especially true along the streams in built-up areas, where the sheep do not have access. Along, for example, Sandá or Hoydalsá in Tórshavn, you can encounter up to 60 different plant species during summer, including forget-me-not (Myosotis scorpioides) and marsh-marigold (Caltha palustris) as well as invasive species such as European speedwell (Veronica beccabunga) and yellow monkey flower (Mimulus guttatus).

Both lakes and streams are habitats for a variety of insects. Along the streams, you can encounter several species of the brownish, nocturnal moth-looking caddisflies, whose larval stage is completed in the cool, flowing water. Among the Faroese caddisflies, there are both species with larvae that cement grains of sand and gravel together into transportable houses, and species where the larvae sit at the bottom of a silk net that captures the small animals that make up their food. There is also the widely prolific Rhyacophila dorsalis, whose larvae are free-living and hunt prey on the bed of the stream. Lake fly larvae (Chironomidae spp.) also occur in large numbers in the streams, where they constitute an important food source for many fish and birds.

Lake fly larvae can also be found in the lakes, where they can be found on the bottom of even deep lakes. The lakes are also habitat to snails and sand-hoppers, as well as several species of house-building caddisflies, whose larvae, unlike their streamdwelling relatives, most often build their houses from plant parts. In small, shallow lakes, you can encounter beetles such as the large diving beetle Agabus bipustulatus, while water boatmen are represented by two species that swim on their front: Callicorixa wollastoni and Arctocorisa carinata.

The three-spined stickleback (Gasterosteus aculeatus) is abundant in both streams and lakes. The eel (Anguilla anguilla) also occurs in lakes and streams, but has declined dramatically since the 1970s. Moreover, the European flounder (Platichthys flesus) sometimes migrates into streams and lakes, but it cannot reproduce in fresh water.

There is trout (Salmo trutta) in almost all streams. The sea trout, which is an ecological form of the trout that migrates into the sea after spawning, is also found in the Faroe Islands, especially in Saksunarvatn and Sandsvatn. It is popular among anglers and as a food item, and towards the end of the 19th century it was caught in such large numbers that the population declined markedly. Leynavatn on Streymoy has an original population of Arctic char (Salvelinus alpinus), and the species has been released in a dammed lake at Vestmanna, from where it has spread to a few other dammed lakes. For the sake of anglers, rainbow trout (Oncorhynchus mykiss) has also been released in Nesvatn on Eysturoy.

Although certain streams bear names such as Laksá and Laksará, salmon (Salmo salar) is unlikely to have occurred naturally in the Faroe Islands until Føroya Sílaveiðifelag (the Faroese fishing club) in 1947 began releasing Icelandic salmon fry into the streams. This has led to the islands today having a self-reproducing salmon population.

The utilisation of the fresh waters

The fresh waters are popular among anglers, but are also used as drinking water and for the production of electricity. For example, more than 100 streams from different rainfall areas were led through collection tunnels to the dam at Eiðisvatn in connection with the large hydropower project at Eysturoy. In addition, fresh water is used commercially by, for example, filleting factories and for the production of salmon fry. The total ecological consequences of the extensive exploitation of the fresh waters are still unknown.

Further reading

• Climate on the Faroe Islands
• Fens on the Faroe Islands
• Geology on the Faroe Islands
• Lakes on the Faroe Islands
• Landscapes and coasts on the Faroe Islands
• Nature and environmental management
• Plant life on land on the Faroe Islands
• Streams on the Faroe Islands
• The sea around the Faroe Islands
• Weather conditions on the Faroe Islands
• Wildlife on the Faroe Islands

Read more about Nature and landscape on the Faroe Islands