Its construction by damming the Gwash valley near Empingham was completed in 1975. During its construction, it was known as Empingham Reservoir. It flooded six or seven square kilometres of the Gwash valley as well as the side valley at the head of which lies Oakham. Nether Hambleton and most of Middle Hambleton were demolished and their wells were plugged as part of the ground preparation. Their neighbouring village of Upper Hambleton survived, and now sits on the Hambleton Peninsula. The Gwash makes a net input to the lake but its flow downstream is maintained. Most of the stored water is extracted from the River Welland at, between Tinwell and Stamford and from the River Nene upstream from Peterborough, a city which is a major user of the water. Because much of the valley is clay, material for the dam was extracted from pits dug within the area that would be subsequently flooded. The clay dam is high, and around long. At its base, it is up to wide, and the finished structure has been landscaped to blend in with the environment, even when viewed from Empingham, the nearest village. Rutland Water contains a limnological tower for study of the reservoir's ecological conditions.
Community
Upper Hambleton and the remnant of Middle Hambleton, including the Old Hall, are now known simply as Hambleton and are to be found on a long peninsula in the middle of the lake; land which was formerly a ridge between the two valleys in which the lake now lies. The few houses of Normanton avoided flooding although its church did not. The lower part of the building was supported against water damage so that its upper part could be used to present the story of the construction of the reservoir to the public. Some funerary monuments from it can be seen at Edenham church, Lincolnshire.
Recreation
The reservoir is used not just for water storage, but is a popular sports centre – as well as water sports such as sailing visitors enjoy fishing, walking and cycling along a perimeter track. A pleasure cruiser, the Rutland Belle, carries people around the lake. Birdwatching brings visitors from far afield. The former butterfly centre at Sykes Lane has been turned into Bugtopia – The Zoo.
The Anglian Water Birdwatching Centre, located in Egleton, features a gift shopoperated by the Leicestershire and Rutland Wildlife Trust and a shop selling binoculars and telescopes. The centre includes the Rutland Environmental Education Centre, exhibits, and windows overlooking the wetlands. The LyndonVisitor Centre is located on the reserve's south shore. There are exhibits, bird viewing windows, trails and hides.