United Utilities is to create a £125m water link between Liverpool and Bury in order to ensure supplies remain accessible across the North West during droughts and periods of maintenance work.
The Warrington-based company is planning a 33-mile route between the Prescot reservoir in Merseyside and the Woodgate Hill Reservoir in Bury.
Talks with more than 200 landowners and eight councils have already begun.
The scheme, which will involve the construction of 15 separate tunnels to cross obstacle including the M6, M61, M66, River Irwell, River Roch, and the West Coast Main Line is expected to take two years to complete, with work beginning early next year.
Ian McAulay, UU's managing director of capital programmes, said: "Pipelines like this are the motorways of the water supply network and this will be one of the biggest engineering projects we have ever undertaken.
"It is all part of our long-term plan to make sure we keep reliable water supplies on tap for our seven million customers in the North West."