Dorchester aqueduct longer than first thought after study

Experts have discovered that the Dorchester aqueduct, which is one of the longest Roman watercourses in the country, is two kilometres longer than first thought.

The aqueduct was a vital part of Roman life in Dorchester, supplying water for the town’s public baths, fountains and wealthy households.

An excavation found traces of the aqueduct upstream of where the source was previously thought to be (Image: Bournemouth University) Archaeologists at Bournemouth University are hoping this discovery adds to an existing understanding of Dorset’s history and how Dorchester, then known as Durnovaria, grew into a strategically important settlement during the Roman occupation of Britain.

Harry Manley, of the university’s department of Life & Environmental Sciences, led the research.

He said: “This aqueduct has been investigated by archaeologists for over a century.

“Despite extensive examinations in the 1990s, the source of its water and the upper sections of its course have never been conclusively mapped, until now.”

It was first suggested that the source of the aqueduct, which followed a winding 20-kilometre route up the Frome valley north west of Dorchester, was a lake in Steppes Bottom.

From left: Sarah Elliott, Harry Manley and Mark Johnson at the site (Image: Bournemouth University)

New surveys and archaeological investigations as part of this new study however found evidence that its route headed further upstream, to the village of Notton on the River Frome.

Mr Manley started his research by studying publicly available Light Detection and Ranging (LiDAR) data, which allowed him to trace the elevation and physical features of the land upstream of Steppes Bottom. The data suggested that the aqueduct followed a path further north.

Map showing route of aqueduct to Notton (Image: Britannia Journal, Cambridge University Press) He was also able to compare this to a geophysical survey carried out by Bournemouth University during a previous study at Frampton Villa, which lies further along this newly identified route, at Nunnery Mead.

Mr Manley said: “That geophysical survey revealed signs of a narrow channel running northwest to southeast. This matched up with my findings from the lidar data, so it seemed like the smoking gun that proved the aqueduct ran through the area.”

The BU team then carried out a ground penetrating radar survey to confirm the existence of the extended waterway, and followed this up with a small excavation, during which they found evidence of the wood line aqueduct channel.

Mr Manley added: “Getting water supplied into prominent structures and buildings in the town would have been a sign of modern living at the time, and an indicator of the town’s status.

“For the citizens of Dorchester to have this aqueduct constantly providing them with fresh water would have been a matter of civic pride. Understanding more about how it was constructed and maintained, and where it began, adds further detail to this vital aspect of Roman life.”

The study is available to read in the scientific journal, Britannia.