One of the neatest feats of Roman engineering in the region is one of the least known. It is the 9.5km line of the Roman aqueduct leading into the old fort of Great Chesters from the NE, a little to the north of Haltwhistle.
Only very faint traces of it remain today, but the logistics of the little water supply project are impressive. Basically, when Great Chesters fort was built on the Wall it didn’t have a nearby water supply, so it had to be piped in from the Caw Burn, about 4km to the NE (more specifically, Saughy Rigg Washpool near Fond Tom’s Pool). However, as the engineers had to rely purely on gravity, the path of the aqueduct took a long and curling route through a 9km+ course to pick up every tiny inch of downhill along the way.
The result was a remarkable bendy, twisting affair taking the channel on a constantly downward trajectory at the almost unbelievably gentle gradient of about 1m drop for every 1,000m travelled. And, once more, the flow of water was eased along a simple, unlined water-course about ½ m wide by ¼ m deep, with the occasional small wooden bridge inserted to take it over minor valleys and streams.
The course of the aqueduct is clearly shown on modern-day OS maps (there’s a decent representation here – and scroll down a bit), though it is not so easy to pick out on the ground. Partial earthworks survive, and in other places cropmarks provide the circumstantial evidence.