More images of Stithians Reservoir, Cornwall. The dam is 41.5 m high and 244m wide. It was built at a total cost of £1,125,000 (about £17 million today) (2009 estimate). Usage: There is an Outdoor Activity Centre offering watersports facilities at Stithians Lake. Sailing, windsurfing, kayaking, SUP and canoeing activities available. Non sport activities include bird watching, fly fishing for trout & a campsite.