A regional water supplier is scrambling to work out how to provide enough water if Sizewell C is approved, after the Environment Agency proposed a large cut to the amount it can take from the River Waveney.

EDF, the company behind plans for the new £20billion nuclear plant, insisted today it had a “clear and deliverable” strategy for its water supply.

The proposed nuclear plant will need up to 2.8 million litres of water a day when operating, mainly for cooling, a figure which has increased since plans were first drawn up.

Essex and Suffolk Water (ESW) has long said there is not enough water in the area with the nearest river, the Blyth, being too small.

Instead it planned to pump water from the River Waveney at Barsham to Sizewell to make up for the shortfall.

But those plans have been put into doubt.

The Environment Agency (EA) told ESW in August that it is likely to have to reduce the amount of water it lets it take from the Waveney, because of pressure on the river.

Modelling shows the cut could be up to 60pc, which would mean Sizewell C cannot be supplied from the Waveney.

Simon Barlow, the EA's project manager for Sizewell, said the exact reduction would not become clear until more modelling has been done.

But ESW’s solicitor warned: “The water supply position in the East of England is not favourable with the EA categorising it as being a seriously water stressed area and if the ability to abstract water from the River Waveney were to be capped, there are very few other sources of water available.”

To meet future demand, regardless of Sizewell C, ESW is already exploring a desalination plant at Great Yarmouth, which turns seawater into fresh water.

Other ideas include a sewage effluent reuse plant in Lowestoft, which treats wastewater and puts it back into the system or a new reservoir along the Waveney.

ESW objected to Sizewell C last month and warned there was a “significant risk” it could not meet the plant’s water demands.

But it later dropped its objection after agreeing with EDF that it would not supply it during construction, which would last almost a decade if approved.

To cope with the shortfall during construction, EDF plans to build a temporary desalination plant. That would need to be in place throughout the construction period, but campaigners say it would harm marine life and the beach.

ESW now has until 2030 to work out how to supply Sizewell. EDF said that was ample time, but it is not clear where that water will come from.

An EDF spokesman said the water supply was secure because even if the amount ESW can take from the Waveney is reduced, it would identify “new resources”.

They added: "There will be no impact on the supply of water to local communities from any stage of the Sizewell C project."

But Pete Wilkinson, chairman of campaign group Together Against Sizewell C (TASC) said EDF was in a “desperate” situation. “They have known about this requirement to provide huge amounts of water to the site for a decade but they still have not got a strategy.

“They have left it to the last minute to come up with a cobbled together plan.”

At the end of September ESW and EDF signed a “statement of common ground” in which ESW said it would drop its objection to the new plant as long as it could not be sued for failing to supply water to Sizewell C during construction. In return it agreed to supply water by 2030.

What happens now?

It falls to a national body called the Planning Inspectorate to decide whether or not to give Sizewell C permission. That decision is expected next year, but even if approved funding issues could cause further delays. EDF owns 80% of the project and Chinese state-controlled nuclear power company CGN owns the remaining 20%.

If built, the two new reactors at Sizewell C can generate enough electricity for six million homes. Supporters say it is much cleaner than burning fossil fuels and will create hundreds of local jobs. But campaigners have raised fears about the impact on wildlife, tourism, and years of disruption to communities during the building phase.