Carsington Water is a reservoir, operated by Severn Trent Water, between Wirksworth and Kniveton in Derbyshire, England. The reservoir takes water from the River Derwent at Ambergate during winter months, pumping up to the reservoir by 10.5-kilometre (6.5 mi) long tunnels and aqueduct. Water is released back into the river during summer months for water abstraction and treatment further downstream. It is England's ninth-largest reservoir with a capacity of 36,331 megalitres.