An RAF Chinook helicopter flies in sandbags for a second day (Picture: PA).
A Chinook based at RAF Odiham is continuing to drop hundreds of tonnes of aggregate to try and shore up the Derbyshire dam at risk of collapse.
Two teams from the Joint Helicopter Support Squadron are loading the aggregate onto the Chinook and then flying and depositing the sandbags onto the dam.
More than 300 tonnes were dropped on Friday, with the same expected on Saturday having started at 04:30 BST.
Water levels at the Toddbrook Reservoir in Whaley Bridge have been reduced by half a metre since Thursday but the damage to the 180-year-old structure remains at a "critical level".
The Government has warned that there is still a threat to life in the town and urged residents to remain patient.
The Met Office has issued a yellow weather warning for much of northern England and the Midlands on Sunday, which includes the area around the reservoir.
It warns there could be damage and disruption from floodwater and lightning strikes.
Toddbrook Reservoir, which contains around 1.3 million tonnes of water, has seen "extensive" damage during the flooding and images appear to show a huge hole in the dam wall.
Prime Minister Boris Johnson promised that the damaged reservoir would have a "major rebuild" as he met locals at nearby Chapel-en-le-Frith High School, which is being used as an evacuation centre.
Describing the damage to the dam as "pretty scary", he said:
"The plan is to try and stop the dam breaking, clearly. And so a huge amount of effort is going into that."
Labour leader Jeremy Corbyn also visited the damaged dam, thanking the RAF "who have worked so hard to protect the community".
The RAF Chinook and around 150 firefighters using high-volume pumps appear to have partly stabilised the reservoir's spillway, with further pumps brought in by officials on Friday.
Watch: more than 300 tonnes of aggregate were dropped on Friday
Those evacuated from their homes were allowed to return briefly on Friday evening to pick up any vital items or pets.
The operation allowed just one person from each household to return for a maximum of 15 minutes.
Derbyshire Police said that any residents who re-entered Whaley Bridge would be doing so at their own risk and that the threat to life remained high.
Around 1,000 people were evacuated from the town but most found their own accommodation with family and friends, according to Derbyshire County Council.
Police have closed railway lines in the Whaley Bridge area over the risk of potential flooding which is due to continue into the weekend.
The reservoir is on the north-west edge of the Peak District National Park and was built in 1831, according to experts, although the Environment Agency records it as being built in 1840-41.
According to a 2011 Environment Agency report on national dam incidents, Toddbrook "has a history of leakage".