Valehouse (or Vale House) Reservoir is a man-made lake in Longdendale in north Derbyshire. It was built between 1865 and 1869 as part of the Longdendale chain, which was built to supply water from the River Etherow to the urban areas of Greater Manchester while maintaining a constant flow into the river. The upper reservoirs supply the drinking water, while Vale House and Bottoms are compensation reservoirs which guarantee the flow of water to water-powered mills downstream. Valehouse, with a crest elevation of 503 m, is too low to supply water under gravity to the Mottram tunnel, so could not be used as an impounding reservoir. Today 45 megalitres of compensation water are released each day into the River Etherow.