The Roman Aquaduct

The picture below shows the site of a Roman water reservoir, or castellum aquae. It was built on to the inside of the northern defensive wall. Its base is marked out in the grass. Standing on a rubble foundation about 5 metres deep, the reservoir was 16 metres long and lined with opus signinum, waterproof cement. It could hold about 12,000 litres of water. It was possibly one of several supplying the colonia's needs.

The Roman colonia's water supply and distribution system were highly complex, and are of national significance. The aqueduct, reservoir, puplic baths and drainage system were probably conceived as a single intergrated scheme.

Public baths played an important role in Roman urban life. A focus for socialising and thought to improve well-being, the baths were large complexes, requiring vast quantities of water and fuel. Lincoln's baths were in the north-eastern quarter of the colonia. Hypocausts (under-floor heating), tessellated pavements, samian pottery from Gaul and glassware, as well as evidence of nearby shops, have all been found in the vicinity. The baths were not used after AD350, a sign that the elite no longer considered public amenities a priority.

The 20th-century solution to Lincoln's water problems was to pump water from Elkesley, Nottinghamshire, 20 miles away. Two thousand years earlier, Roman engineers faced a similar problem of having to pipe water uphill from some distance to supply the colonia, but without the benefit of steam or electric engines.

People dug wells and collected rainwater for everyday needs, but these sources could not supply all the public works of the colonia. A pipeline was therefore constructed, which stretched north eastwards for over a mile, at least as far as a spring known as Roaring Meg. The pipe was made of clay and encased in opus signinum. Near this possible source, a bridge to carry an aquaduct was built. Some of the bridge pillars have been excavated.

But how did it work? Normal gravity flow was not possible here, as the spring was about 30 metres lower than the colonia reservoir. Perhaps a raising device, such as a bucket system or force pump, was used to lift water into the aquaduct.

Another suggestion is that the source of the water was much further away and higher up, so that the flow could operate by gravity. The bridge pillars would then have been part of a much larger construction: in some Roman cities, water was piped from as far as 30 miles away. However, no evidence of pipes from greater distance than Roaring Meg has been found yet.

To add to the mystery is the state of the pipes: the absence of lime deposits could suggest that water never passed through them. One conclusion could be that the sytem was built, but then never worked. There are instances of such failed grand schemes in other parts of the Empire.

Wherever the colonia's water came from, there is no escaping the problem that special techniques would have been required to feed it into the colonia. The question therefore remains: how exactly was Lincoln supplied with water in Roman times?