Roman aqueduct

The ancient Romans constructed numerous aqueducts (Latin "aquaeductūs", sing. "aquaeductus") to supply water to cities and industrial sites. These aqueducts were amongst the greatest engineering feats of the ancient world, and set a standard not equalled for over a thousand years after the fall of Rome. Many cities still maintain and use the ancient aqueducts even today, although open channels have usually been replaced by pipes.The Romans typically built numerous aqueducts to serve any large city in their empire, as well as many small towns and industrial sites. The city of Rome itself, being the largest city, had the largest concentration of aqueducts, with water being supplied by eleven aqueducts constructed over a period of 500 years. Scholars can even predict the size of the city by its water supply. They served potable water and supplied the numerous baths and fountains in the city, as well as finally being emptied into the sewers, where they performed their last function in removing waste matter. The methods of construction are well described by Vitruvius in his work De Architectura written in the first century BC. His book would have been of great assistance to Frontinus, a general who was appointed in the late first century AD to administer the many aqueducts of Rome. He discovered a discrepancy between the intake and supply of water caused by illegal pipes inserted into the channels to divert the water, and reported on his efforts to improve and regulate the system to the emperor Nerva at the end of the first century AD. The report of his investigation is known as De aquaeductu. In addition to masonry aqueducts, the Romans built many more leats; channels excavated in the ground, usually with a clay lining. They could serve industrial sites such as gold mines, lead and tin mines, forges, water-mills and baths or thermae. Leats were very much cheaper than the masonry design, but all aqueducts required good surveying to ensure a regular and smooth flow of water.The aqueducts required very careful planning before building, especially to determine the water source to be used, the length of aqueduct needed and its size. Great skill was needed to ensure a regular gradient, so that the water would flow smoothly from its source without the flow damaging the walls of the channel. As the need for water grew, extra sources would be utilised, very often making use of existing structures as with the Aqua Claudia and Anio Novus in Rome. The problems of aqueduct building and use are described by Vitruvius and Frontinus, the latter producing a long report on the state of the Aqueducts of Rome in the last years of the first century AD.Several surveying tools were used in the construction of Roman aqueducts, one example being the "chorobaes". The chorobaes was used to level terrain before construction. It was a wooden frame supported by four legs with a flat board fitted with a water level. Another tool used in the construction of the aqueduct was the "groma". Gromas were used to measure right angles. A groma consisted of stones hanging off four sticks perpendicular to one another. The instrument which is the forerunner of the theodolite was known as the dioptra, and was used to measure vertical angles.Many aqueducts were built to supply water to industrial sites, such as gold mines, where the water was used to prospect for ore by hydraulic mining, and then crush and wash the ore to extract the gold. They usually consisted of an open channel dug into the ground, with a clay lining to prevent excessive loss of water and sometimes with wooden shuttering. They are often known as leats. However, they were built just as carefully as the masonry structures, but often at a higher gradient so as to deliver the greater volumes needed for mining operations. . The remains of such leats are visible today at sites like Dolaucothi in south-west Wales, and at Las Medulas in northwest Spain. These sites show multiple aqueducts, presumably because they were relatively short-lived and deteriorated rapidly. There are, for example, at least seven major leats at Las Medulas, and at least five at Dolaucothi feeding water from local rivers direct to the minehead. The palimpsest of such channels allows the mining sequence to be inferred.