A £1.2 million scheme to transform a former china clay quarry into a new reservoir supplying Cornwall for generations to come starts today.

South West Water purchased Stannon Lake, on Bodmin Moor, from minerals extraction company Imerys in 2008. It was a working quarry until 2002.

Stannon Lake, near Crowdy reservoir on the northern edge of the moor, holds over 8 billion litres of water, equivalent to 3,200 Olympic swimming pools, and is around 60 metres deep.

Once constructed, two shore-based pumps will transfer up to six Megalitres of water a day into the raw water network via a 1.1km pipe. The water will then be treated at either De Lank Water Treatment Works near St Breward or Lowermoor Water Treatment Works near Camelford.

Project manager Nol Vincent said: “Our aim is to safeguard water supplies for our customers, whatever climate change throws at us. The development of Stannon Lake gives us significant extra reserves, without the cost and disruption involved in building a new reservoir – a process which can take 20 years.

“Stannon will be used to boost our water resources in Cornwall and will make a significant impact.”

Stannon will be the second largest reservoir in Cornwall, behind Colliford. Once fully operational at the end of the summer, Stannon will take its place after Roadford, Colliford and Wimbleball as the fourth largest reservoir in the South West.

Stannon is the second former china clay pit to become a reservoir. Park Lake, which is near Siblyback and Colliford reservoirs on the southern edge of Bodmin Moor, was bought from Imerys in September 2006. The 55-metre deep lake holds around 7.7 billion litres of water – or the equivalent of 3,080 Olympic swimming pools. It became operational in spring 2009.