The 4.5 mile (7.2km) Rivelin Tunnel runs between the Upper Derwent Valley reservoirs and Rivelin Reservoir. It was built between 1903 – 1909 and the portal has a datestone of 1910.
The Derwent Valley Water Board was founded in 1899. One of it’s obligations was to deliver Sheffield share of ‘compensation’ water from the Howden and Derwent Reservoirs (Upper Derwent Valley Impoundment Scheme), to Rivelin Reservoir. This was before the Ladybower Reservoir was built. Construction of the tunnel required three in-line surveyors sighting towers. The one above Stanage Edge is the observatory tower at the mid-point, the tallest of the three, and has been demolished. It was once a 40 foot structure allowing sighting to the east pillar on Oaking Clough Conduit and the west pillar on Bamford Moor. The tunnel falls just 2 metres along the 7.2km length. The remaining building here was a store for surveying equipment and later may have been used as a blasting powder store for the Stanage End quarries.
The engineering skill required to dig this tunnel by hand in 1903 was considerable.
Included are photographs of the remaining three sighting pillars. The Observatory Tower was much taller at 40 foot than the west and east towers of 8 feet.
The outlet portal into the Lower Rivelin Reservoir is a few metres upstream from the Wyming Brook. It flows continuously, and more water comes out from the tunnel than enters it at the Ladybower end. This is because the tunnel is unlined and natural seepage from the moor adds to the volume.
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Writings and photographs courtesy of Mike Browell.