Construction of the huge concrete reservoir is set to take about four years and will be carried out in two phases.
The main construction works are due to start imminently and will involve the excavation, construction and commissioning of a new 100m by 130m twin compartment concrete reservoir next to the old one.
Once finished the old reservoir will be decommissioned and a new smaller reservoir built within its foot print.
The staged programme allows water to be supplied to Severn Trent customers while construction is underway and reduces the use of environmentally intrusive pipelines.
Currently Ambergate reservoir holds 128m litres of water and is the tap supply for the East Midlands.
The present structure has been in use for more than 100 years and has deteriorated badly.
Duncan Wratten, Severn Trent’s project manager, said: “Options to refurbish the existing reservoir were taken into account, however following careful consideration it was agreed that a new reservoir would need to be constructed in order to continue the supply of quality water to Severn Trent’s customers.”