Thirlmere

Thirlmere is a reservoir in Cumbria’s Lake District, set between the Helvellyn ridge to the east and fells such as Armboth Fell and Raven Crag to the west. It runs roughly south to north and is bordered on one side by the A591 road and on the other by a minor road. The water body occupies the site of a former natural lake which was so narrow at its waist that it was sometimes regarded as two separate lakes. In the 19th century Manchester Corporation built a dam at the northern end, raising the water level and flooding the valley bottom to create the reservoir. The Thirlmere Aqueduct, 96 miles long, carries water from the reservoir to Manchester. The reservoir was proposed as early as 1863 to supply London, but the scheme was dismissed by a Royal Commission chaired by the Duke of Richmond. Manchester Corporation later sought its own supply, noting rising demand from 8 million gallons a day in 1855 to 21 million at peak in 1874. The reliable output from existing reservoirs was only 2.4 million gallons daily in drought, and demand threatened to outstrip supply within seven years. Engineers pointed out that Thirlmere’s catchment area covered over 11,000 acres with an annual rainfall of about 110 inches, yielding up to 50 million gallons a day. Visitors today find a long, narrow lake framed by fells and bordered by roads on either side. The surrounding hills, including Helvellyn, Armboth Fell and Raven Crag, offer views across the water. A path runs along the eastern shore close to the A591, while quieter tracks follow the western shore. The reservoir still supplies Manchester’s water, managed by United Utilities. The landscape combines open water with rugged fells, reflecting both natural beauty and the engineering legacy of the 19th century.