Thirlmere is a reservoir in the English Lake District
with a dam at the northern end and is bordered on the eastern side by
the A591 road and on the western side by a minor road.
Prior to the construction of the reservoir the site
was occupied by two smaller lakes - Leathes Water and Wythburn Water.
The growth of the industrial city of Manchester
during the 19th century had led to an increased demand for water so the
water level was raised by construction of a dam by the Manchester
Corporation at the northern end of Thirlmere, in 1890–1894.
The reservoir was then able to supply water to
Manchester via the Thirlmere Aqueduct, approximately 100 miles long.
The name is sometimes also applied to the whole
valley, which connects Grasmere in the south with the Vale of Keswick in
The Helvellyn ridge lies to the east and to the west
are a number of fells including Armboth Fell and Raven Crag both of
which give views of the lake.