Seven miles of new pipes are being installed to deliver clean drinking water to more than 165,000 people in Edinburgh and the Lothians.

The pipes, which begin at the foot of the Pentland Hills, are being laid at a rate of around 75m per day.

They will surge through practice trenches which date back to the First World War, with experts on hand to make sure any archaeological remains are located and recorded.

Other challenges facing Scottish Water include digging a tunnel crossing under the busy A702 Biggar Road near Hillend.

When completed, the £20m project will link Marchbank and Glencorse water treatment works.

In future it could also be linked with water supplies across the south of Scotland.

Scott Fraser, Scottish Water regional corporate affairs manager, said: "It is exciting to see the start of this essential project to make the water supply for many of our customers more resilient.

"As always, we thank everyone impacted by our works for their patience and understanding."