Blelham Tarn
A derelict boathouse extending out onto a lake
The boathouse on the tarn in 2007
Blelham Tarn is located in the Lake District
Blelham Tarn
Blelham Tarn
Blelham Tarn is located in the former South Lakeland district
Blelham Tarn
Blelham Tarn
Location in South Lakeland, Cumbria
LocationCumbria
Coordinates54°23′44″N 2°58′41″W / 54.39556°N 2.97806°W / 54.39556; -2.97806
Typenatural
Etymologydark blue pool[1]
Primary outflowsBlelham Beck
Max. length0.66 km (0.41 mi)[2]
Max. width0.257 km (0.160 mi)[1]
Surface area11 ha (27 acres)[2]
Average depth6.8 m (22 ft)[2]
Max. depth14.5 m (48 ft)[2]
Water volume717,829 cubic metres (582 acre⋅ft)[2]
Residence time50 days[3]
Surface elevation47 m (154 ft)[2]

Blelham Tarn is a large valley tarn in the Lake District of England, to the north of the hill Latterbarrow. The settlements of Outgate, Low Wray 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.[4] Fish species in the tarn include brown trout, eel, perch, pike and roach,[5] much of the tarn shore is reedbed and waterfowl present can include great crested grebe, whooper swan and golden-eye.[6]

The tarn is regularly monitored by the United Kingdom Lake Ecological Observatory Network and is characterised as eutrophic and monomictic[3] and has suffered from agricultural water pollution[7] with large quantities of blue-green algae in the summer.[5] 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.[8]

Blelham Tarn and Bog, with a total area of 49 hectares, is designated a site of special scientific interest[9] and Blelham Bog is designated a National Nature Reserve[6] The bog contains various species of sphagnum moss, bog myrtle, cotton-grass and the white-beaked sedge; and rare caddis-flies and vertigo lilljeborgi.[6]

References

  1. 1 2 Blelham Tarn
  2. 1 2 3 4 5 6 "Blelham Tarn Water Body ID 29270". UK Lakes Detail. NERC Centre for Ecology and Hydrology. Archived from the original on 11 June 2016. Retrieved 23 May 2016.
  3. 1 2 "UKLEON: United Kingdom Lake Ecological Observatory Network". Archived from the original on 24 March 2015. Retrieved 25 November 2014.
  4. ↑ Blelham Tarn & Bog - Unit 2
  5. 1 2 Blelham Tarn
  6. 1 2 3 Cumbria's National Nature Reserves
  7. ↑ Blelham Tarn & Bog - Unit 6
  8. ↑ "Data from the UK Lake Ecological Observatory Network". Archived from the original on 4 March 2016. Retrieved 25 November 2014.
  9. ↑ SSSI units for Blelham Tarn & Bog
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