The River Etherow rises on the eastern flank of Black Hill and flows west down the Longendale valley to eventually join with the Goyt near Marple. Near Stockport the Goyt then joins the Tame to become the River Mersey.
The source of the Etherow is Salter's Brook at Wike Head, to the east of Black Hill, and the stream flows initially south, forming the Derbyshire - Yorkshire border before turning westwards into Longendale.
Once heavily wooded, even into the last century, Longendale is now a fine open valley with a series of reservoirs constructed by the Manchester and Salford Waterworks Company between 1848 and 1877. Relics of the oak woodland remain around some of the northern slopes of Bleaklow and at the eastern end of the valley.
When they were built the Longendale dams were the largest project of their type and cost the huge sum of 3 million pounds. Their construction posed numerous technical problems because much of the land in the bottom of the valley proved to be rubble from landslips with solid rock some way beneath the surface. This caused the first Woodhead dam, finished in 1851, to leak so badly that it had to be rebuilt lower down in 1863 and the modern dam is really these two dams joined together. Torside was built at the same time and also suffered construction problems.
Rhodeswood reservoir was the next to be built and in 1865 two smaller reservoirs, Valehouse and Bottoms, were begun downstream close to Tintwhistle, where the river leaves the valley to begin its journey through the Manchester conurbation. Valehouse flooded a cotton mill and small village and the upper valley was deliberately depopulated at this time to ensure that the water supply was not contaminated.
Woodhead Chapel from Woodhead dam
The only reminder of the people who once lived here and the navvies who constructed the dams and the Woodhead railway tunnels is the small chapel above the main road between the Woodhead and Torside reservoirs. The chapel is thought to have been here since 1487 but the present building was begun in 1730 and there have been several rebuildings since. It is currently in a poor state of repair. In the graveyard are the graves of generations of local farmers and of several men who died in the construction of the first Woodhead tunnel around 1842, and others who died in 1849 during the construction of the second tunnel, when there was an outbreak of cholera.