Work has started on a £750,000 project to install three huge pipes in the dam at Pitsford reservoir.
From this week, Anglian Water will need to work across the dam, meaning the roadway will be shut for about four weeks.
Steve Parker, project manager for Anglian Water, said: “We know that many people visit Pitsford Water Park to enjoy the beautiful countryside by walking, biking or even jogging around the reservoir.
“This is why we’ve arranged for a temporary footpath to be available whilst the dam can’t be crossed to allow visitors to continue enjoy what’s there, as they would normally.”
The project will allow the company to rapidly reduce the amount of water in the reservoir if it was ever required in future.
Mr Parker said: “We’re installing three pipes, each one is 100 metres long and 24 inches wide and together they will be able to suck 5,000 litres per second out of the reservoir, doubling the current rate water can be pumped out.
“Once complete, it would be possible to drain 50 per cent of the reservoir – some eight billion litres of water – in less than three weeks.
“While it is incredibly unlikely that we’ll ever have to rapidly pump water out of the reservoir at Pitsford, it’s important we would be able to do it safely if it were ever needed.
“It’s an essential part of the management responsibilities we have to fulfil when we are in charge of a large body of water.”
Work got under way at the start of March underneath and alongside the dam to install the supporting power and vacuum pipework.