1500 bags of heather have been airlifted onto Turley Holes Moor
Helicopters are being used as part of a major effort to help conserve eroded peat moorland in Calderdale.
They are being used to airlift large bags of cut heather to Turley Holes Moor near Hebden Bridge with the aim of stopping further peat erosion.
It is also hoped new heather growth will help stop peat washing away into streams which feed nearby reservoirs.
Water containing peat has to undergo costly extra filtration before it is fit for human consumption.
Around 1500 bags of cut heather have so far been airlifted into Calderdale as part of the Moorlife project.
The aim of reintroducing vegetation on to the bare peat at Turley Holes Moor is to stabilise it which, in turn, will cut down on erosion.
It will also mean water coming off the moors will need less treatment before it enters the domestic supply.
Mike Pearson, from Yorkshire Water, said the work was essential if water quality was to be maintained.
"When they turn the taps on, our customers expect to have clear water," he said.
"The water which comes off these moorlands comes off with peat and sediment in it.
"That generates colour which, with the sediment, then has to be stripped out of the water if it is going to be clear for our customers."
The work on Turley Holes Moor is part of one of the biggest ever conservation schemes carried out in the UK.
It will see peat moorland at a number of sites in the South Pennines restored at a cost of £5.5m.
After being delivered by helicopter much of the the cut heather will be spread by hand by contractors and volunteers.
As part of the Moorlife project, much of the heather is being spread by hand
It is hoped that the heather will not only protect peat moorland from further erosion but will also encourage the growth of peat moss.
Mike Pilkington, from the Moorlife project, said: "This moss is very important for taking carbon from the atmosphere and storing it in the peat.
"It will also make it a better environment for wildlife and for people."
It is expected that around 24,000 bags of cut heather will be spread on four sites stretching from Calderdale to the Peak District.
Over 1.6m sq km of bare and eroded peat moorland in the South Pennines is being conserved in this way during the five year Moorlife project.