Water from the River Severn and Lake Vyrnwy in the UK could be transported to London to tackle potential shortages.
The Thames Water plan would see water from Lake Vyrnwy piped into the River Severn and then to the south-east of England and London.
The plan, which is part of a consultation being run by Thames Water on future supply for the region, said it would work either by building a new pipeline – or using restored canals.
A report outlining the long-term timescale of the plan states: "Planning consent for construction is planned by 2040 with water available from 2050 in a phased manner. The scheme would supply water for Affinity Water, Southern Water and Thames Water customers."
Severn Trent has confirmed it is looking at options for future water supply alongside Hafren Dyfrdwy – but said no options are certain.
A spokesman said: “As required by legislation and to address the challenges of population growth right across the UK, Severn Trent and Wrexham-based Hafren Dyfrdwy are exploring many options to meet water demand from 2050 and beyond.
"All options being explored are currently proposals, none are certain."
The Thames Water consultation says the water would "be moved from the River Severn to the River Thames either by a new pipeline or by a combination of new pipeline and restoring the Cotswold canals".
Thames Water says the proposals could be required as it forecasts needing an extra one billion litres of water every day for customers by 2075 – to accommodate both climate change and population growth.
New pipeline could transfer water to UK capital in event of drought
