Blagdon Lake ST515597 lies in the Chew Valley at the northern edge of the Mendip Hills, approximately 10 mi (16 km) south of Bristol, England. The lake was created by Bristol Water (Bristol Waterworks Company as it was known then), when it dammed the River Yeo, starting construction in 1891 and completing this in 1899. The Wrington Vale Light Railway was constructed primarily to bring building materials for the lake.
The lake still provides drinking water, but also acts as a fishing lake and nature reserve. The original suction tanks are now used for trout rearing.