Chew Valley Lake () is a reservoir in Chew Stoke, Chew Valley, Somerset, England. It is the fifth-largest artificial lake in the United Kingdom, with an area of . The lake, created in the early 1950s, was opened by Queen Elizabeth II in 1956. It provides much of the drinking water for the city of Bristol and surrounding area, taking its supply from the Mendip Hills. Some of the lake water is used to maintain the flow in the River Chew. Before the lake was created, archaeological investigations were carried out that showed evidence of occupation since Neolithic times and included Roman artefacts. The lake is an important site for wildlife and has been designated a Site of Special Scientific Interest (SSSI) and a Special Protection Area (SPA). It is a national centre for birdwatching, with over 260 species recorded. The lake has indigenous and migrant water birds throughout the year, and two nature trails have been created. The flora and fauna provide habitats for some less common plants and insects. Some restricted use for recreational activities is permitted by the owner, Bristol Water, including dinghy sailing and fishing, primarily for trout. Location Chew Valley Lake is in the Chew Valley at the northern edge of the Mendip Hills, surrounded by meadows and woods and close to the villages of Chew Stoke, Chew Magna and Bishop Sutton. When it was built in the 1950s, its 1,200 acres (4.9 km²) were flooded with 4,500 million imperial gallons (20,000,000 m³) of water from the Mendip hills, with a catchment area of 14,000 acres (57 km²). It is shallow, with an average depth of 14 ft (4 m) at top level and a maximum depth of just 37 ft (11 m). It is fed by small rivers, and it flows into the River Chew for 17 miles (27 km) before it joins the Avon to head out to sea. The deepest part is near the dam and the outlet tower, where the steeply sloping shores of Walley Bank and the north shore result in depths of up to 20 ft (6 m). "Denny Island", above the surface throughout the year, is wooded and provides a habitat for wildlife. The lake is owned and operated by Bristol Water, which created it in 1956 when the demand became too large for nearby Blagdon Lake. Working with the Avon Wildlife Trust, Somerset Wildlife Trust and other