What did roman aqueducts look like?

Answer 1

Most Roman aqueducts were underground, 0.5 metres to 1 metre below ground. They were flat-bottomed, arch-section conduits with regular accesses to them.

Conduits above ground were usually slab-topped. Initially they were made of stone brick. Later concrete, which was waterproof, was used. Water was moved by gravity and therefore the aqueducts had to have a gradient. A low gradient was used to prevent damage.

The conduits could be supported by bridgework when valley has to be crossed or when they were needed to maintain the gradient. They had arches built in stone, brick or cement. When deep valleys had to be crossed the bridges had two or three piers of arches. Then a valley or a depression was too deep or long siphons were used instead. The conduit ended in a tank which fed the water into pipes which run to the lower level of the valley, were supported by a low bridge and ended in a tank lower down which passed the water on to another conduit. This system maintained the desired gradient. The pipes were made of led or, less often, stone or ceramic and sealed with led. They were sometimes reinforced by concrete cases or stone sleeves. The siphons could be vulnerable blockages of blow-out at the lower level where the water pressure was greater and needed careful maintenance. Maintenance was also needed to repair cracks, clear gravel and debris and remove lime scale in areas with hard water which narrowed the passage of water.

Aqueducts were carried by bridges when they crossed valleys or when they were needed to maintain a gradient to move the water over plains. For deep valleys milti-pier bridges with two or three rows of arches were built.

The greatest example of a multi-pier bridge is the Pont du Gard, which was part of an aqueduct which supplied Nimes, in southern France. It has three tiers of recessed arches with the main piers in line one above the other. The first two tiers have very high and wide arches and a third tier has low and narrow arches. It was built to carry an aqueduct to Nimes in southern France. It reaches a height of 48.8 metres (160 feet). The lower tier is 142 metres (466 feet) long and has six aches with a height of 22metres (72 ft.). The second tier is 242 metres (794 ft.) long and has eleven arches 20 metres (66 ft.) high. The upper tier is 275 metre (902 ft.) long. It originally had 47 arches (only 35 have survived) 7 metres (23 ft.) high. The width of the first pier is 6 metres (20th.), that of the second pier is 4 metres (13 ft.) and that of the third pier is 3 metres (23 ft).