Blelham Tarn is a large valley tarn in the

Lake District The Lake District, also known as the Lakes or Lakeland, is a mountainous region in North West England. A popular holiday destination, it is famous for its lakes, forests, and mountains (or ''fells''), and its associations with William Wordswor ...

of England, to the north of the hill Latterbarrow. The settlements of Outgate,

Low Wray Claife is a civil parish in the South Lakeland district of Cumbria, England. It is situated west of Windermere, and east of Esthwaite Water and the village of Hawkshead. In the 2001 census the parish had a population of 392, reducing to 298 ...

and High Wray are close by. The tarn is drained to the northeast by the short Blelham Beck into Windermere. This beck was previously straightened and lowered. Fish species in the tarn include

brown trout The brown trout (''Salmo trutta'') is a European species of salmonid fish that has been widely introduced into suitable environments globally. It includes purely freshwater populations, referred to as the riverine ecotype, ''Salmo trutta'' morph ...

, eel, perch, pike and

roach Roach may refer to: Animals * Cockroach, various insect species of the order Blattodea * Common roach (''Rutilus rutilus''), a fresh and brackish water fish of the family Cyprinidae ** ''Rutilus'' or roaches, a genus of fishes * California roach ...

,Blelham Tarn
/ref> much of the tarn shore is reedbed and waterfowl present can include great crested grebe, whooper swan and golden-eye. The tarn is regularly monitored by the United Kingdom Lake Ecological Observatory Network and is characterised as eutrophic and monomictic and has suffered from agricultural water pollution with large quantities of blue-green algae in the summer. The lake temperature at various depths varied over the period July 2012 to November 2014 between 2 and 25 Celsius as the air temperature (3 m above the surface) varied between -3 and 22 Celsius. Over the same period the pH varied from 6.4 to 9.8 and the dissolved oxygen ranged from 7 to 14 mg/L.Data from the UK Lake Ecological Observatory Network
/ref> Blelham Tarn and Bog, with a total area of 49 hectares, is designated a

site of special scientific interest A Site of Special Scientific Interest (SSSI) in Great Britain or an Area of Special Scientific Interest (ASSI) in the Isle of Man and Northern Ireland is a conservation designation denoting a protected area in the United Kingdom and Isle of ...

SSSI units for Blelham Tarn & Bog
/ref> and Blelham Bog is designated a National Nature ReserveCumbria's National Nature Reserves
/ref> The bog contains various species of sphagnum moss, bog myrtle,

cotton-grass ''Eriophorum'' (cottongrass, cotton-grass or cottonsedge) is a genus of flowering plants in the family Cyperaceae, the sedge family. They are found throughout the arctic, subarctic, and temperate portions of the Northern Hemisphere in acid bog ha ...

and the white-beaked sedge; and rare caddis-flies and

vertigo lilljeborgi ''Vertigo lilljeborgi'' is a species of minute land snail, a terrestrial pulmonate gastropod mollusk or micromollusk in the family Vertiginidae, the whorl snails. MolluscaBase eds. (2023). MolluscaBase. Vertigo lilljeborgi (Westerlund, 1871). A ...

References

{{authority control Lakes of the Lake District National nature reserves in England Sites of Special Scientific Interest in Cumbria South Lakeland District Hawkshead