Heavy rain is expected to hamper efforts to fix a damaged dam at risk of bursting – after more residents nearby were evacuated.
Attempts to lower Toddbrook Reservoir’s water level have once again continued overnight in Whaley Bridge, Derbyshire.
It has dropped by 1.3m (4ft 3ins) since Thursday, but forecasters have said 30-40mm (1.2-1.6in) of rain could fall in just two hours on Sunday.
A further 55 homes were evacuated on Saturday.
Some 1,500 people in the town had already sought shelter elsewhere after part of the reservoir’s spillway broke away.
Police said the “risk of adverse weather” was to blame for the most recent evacuations, as well as the “ongoing risk” of the reservoir breaching.
Derbyshire’s deputy chief fire officer, Gavin Tomlinson, said crews were working to get “ahead of the curve” and “minimise the impact of any bad weather that does materialise”.
‘Not out of the woods’
The Canal and River Trust estimated the reservoir was at 83% of its capacity by Saturday afternoon after 105,000 cubic metres (23 million gallons) of water was pumped out in 12 hours.
An RAF Chinook helicopter put 400 tonnes of sandbags on the affected part of the dam on Friday – adding a further 70 on Saturday.
Daniel Greenhalgh, from the trust, which owns the reservoir and dam, warned: “We are not out of the woods yet.
“The last estimate was that residents could be out of their homes for seven days yet.”
On Saturday, they were allowed briefly into their homes to collect pets and essentials, but were warned they would be doing so at their own risk.
The controlled operation allowed one resident per household back into their homes for 15 minutes.
Police, the Environment Agency, and the Canal and River Trust have all said there is a “real risk” the 188-year-old dam could collapse and flood the town.
The Met Office has issued a yellow weather warning for much of northern England and the Midlands, including the area around the reservoir.
The Canal and River Trust have defended the maintenance and safety of the structure, which was built in 1831.
Mr Greenhalgh said: “This dam was inspected regularly, by us and an independent engineer.
“It needs to be remembered there was a huge amount of rain in a short time and this flooded the area.”
Fire officer Mr Tomlinson said the situation was “absolutely unique” and everyone had been “working till they can’t work any more”.
“Our aim is still the same; to prevent more water getting into the reservoir and working as hard as we can to make sure the dam wall retains its integrity.
“We will have the Chinooks working today [Saturday] dropping bags of ballast, we have specialist contractors putting concrete grouting between the bags of ballast to bind it together to give it more security.”
Prime Minister Boris Johnson visited on Friday and promised a “major rebuild” of the dam.
A helpline for evacuated residents will be operated by Derbyshire County Council from 09:00 BST to 22:00 on Saturday. The number is 01629 533 190.