VARIANT 2. Historical Background: Developments in Water Supply Systems

(continuation)

Extending from a distant spring-fed area, a lake, or a river, a typical Roman aqueduct included a series of underground and aboveground channels. The longest was the Aqua Marcia, built in 144 BC. Its source was about 23 miles (37 kilometres) from Rome. The aqueduct itself was 57 miles long, however, because it had to meander along land contours in order to maintain a steady flow of water. For about 50 miles the aqueduct was underground in a covered trench, and only for the last 7 miles was it carried above ground on an arcade. In fact, most of the combined length of the aqueducts supplying Rome (about 260 miles) were built as covered trenches or tunnels. When crossing a valley they were supported by arcades comprising one or more levels of massive granite piers and impressive arches.

The aqueducts ended in Rome at distribution reservoirs, from which the water was conveyed to public baths or fountains. The water was distributed from large storage cisterns to public fountains and baths by an elaborate system of lead pipes. A few very wealthy or privileged citizens had water piped directly into their homes, but most of the people carried water in containers from a public fountain. Water was running constantly, the excess being used to clean the streets and flush the sewers.

Ancient aqueducts and pipelines were not capable of withstanding much pressure. Channels were constructed of cut stone, brick, rubble, or rough concrete. Pipes were made of drilled stone or of hollowed wooden logs; clay and lead pipes were also used.

During the Middle Ages there was no notable progress in the methods or materials used to convey and distribute water. Water supplies were largely neglected, and epidemics caused by waterborne organisms were common.

In the 17th and 18th centuries, distribution systems utilizing cast-iron pipes, aqueducts, and pumps were installed in London and Paris. However, cast-iron pipes with joints capable of withstanding high pressures were not used very much until the early 19th century. The steam engine was first applied to water pumping operations at about that time, making it possible for all but the smallest communities to have drinking water supplied directly to individual homes.

During the 19th century the pollution of most water supplies became so serious that slow-sand filtration was initiated; and by the end of the century the realization that diseases could be transmitted by water led to the use of sterilizing chemicals, usually chlorine compounds.

Asbestos cement, ductile iron, reinforced concrete, and steel came into use as materials for water-supply pipelines in the 20th century.

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cut stone тёсаный камень

rough concrete неотделанный бетон, бетон после распалубки

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