Seathwaite Tarn

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Seathwaite Tarn

Seathwaite Tarn is a tarn in the Furness Fells of Lancashire North of the Sands, within the Lake District. The tarn is on the saddle between the Old Man of Coniston, which is Lancashire's county top, and Grey Friar (to the north). Above its head, to the east, rises Brim Fell on the ridge between The Old Man and Swirl How.

The tarns sits above the village of Seathwaite, which lies to the southwest in Dunnerdale.

The tarn was considerably enlarged in 1904 in order to provide a drinking water reservoir, for which a dam was biult. During the dam construction some of the navvies rioted damaging buildings in the village, several rioters were shot, one dying the next day.[1]

The dam before repairs and reconstruction in 2010

The dam is almost 400 yards long and is concrete cored with slate buttresses, the resulting depth of the tarn being around 80 feet. Water is not abstracted directly from the tarn, but flows some distance downriver to an off-take weir.

On the slopes of Brim Fell, above the head of the reservoir, are the remains of Seathwaite Tarn Mine. This was worked for copper in the mid 19th century, and also appears as a location in the novel The Plague Dogs by Richard Adams. Rocks in the area were the first confirmed occurrence of wittichenite in the British Isles.

Bronze Age ring cairns were found close to Seathwaite Tarn in 2003, these were excavated in 2003 and 2007.[2]

Seathwaite Tarn has suffered from acidification. An experiment in 1992–1993 to reduce the acidification by using a phosphorus-based fertiliser increased the pH from 5.1 to 5.6 and changed the levels of the different species of the rotifer assemblage significantly.[3]


  1. "Navvyman chapter 4". Navvyman. Coracle Press/Victorianweb. 1983. Retrieved 3 August 2009. 
  2. "Seathwaite Tarn excavation". Lake District National ark website. National Parks. 2007. Retrieved 3 August 2009. 
  3. May, Linda (November 1995). "The effect of lake fertilisation on the rotifers of Seathwaite Tarn, an acidified lake in the English Lake District". Hydrobiologia 313-314 (1): 333–340. doi:10.1007/BF00025966. ISSN 0018-8158 (Print) 1573-5117 (Online). 

54°22′44.66″N 3°9′17.83″W / 54.3790722°N 3.1549528°W / 54.3790722; -3.1549528Coordinates: 54°22′44.66″N 3°9′17.83″W / 54.3790722°N 3.1549528°W / 54.3790722; -3.1549528

Major waters of the Lake District
Cumberland: Bassenthwaite LakeBurnmoor TarnButtermereCogra MossCrummock WaterDerwent WaterDevoke WaterEnnerdale WaterLoweswaterThirlmereWast Water
Cumb. / Westm.: Ullswater
Westmorland: GrasmereHaweswaterRydal Water
Lancs. / Westm.: WindermereElter Water
Lancashire: Coniston WaterEsthwaite WaterSeathwaite TarnTarn Hows