Clean and reliable heating could one day be provided by the flow of the Lea River.

The waterway through east London which runs into the Thames at Bow Creek could supply heat and hot water to tens of thousands of homes and businesses.

It is one of a list of rivers and estuaries, including the lower Thames, which could provide energy using water pumps instead of traditional gas or electricity.

The pumps simply take heat from the water and feed into local networks or buildings.

“It sounds like magic,” Energy Secretary Ed Davey said. “But technology can now extract some heat from rivers to warm homes and offices.

“I want communities to use our waterways for renewable heat. This would cut our import bill and boost home-grown supplies of clean, secure energy.”

So the Environment Department has drawn up an energy map of 40 suitable rivers, including the Lea flowing through Hackney Wick, Old Ford, Canning Town and Poplar, down to the Thames at Blackwall.

The map could help local authorities and developers find prime sites for pumps in areas with high demands for heat, each generating a megawatt of power enough for 500 properties.