THE ROMAN ACQUEDUCTS |
Various vestiges of aqueduct bridges are still in evidence in and around modern Rome. The popular but inaccurate image is that Roman aqueducts were elevated throughout their entire length on lines of arches. Roman engineers were very practical; whenever possible the aqueducts followed a steady downhill course at or below ground level. Inverted siphons, viaducts, and tunnel were used sparingly, when difficult conditions could not be met by any other techniques. The system of aqueducts serving Rome had only 5 percent of its total distance supported by viaducts or bridges.
In the long run, the elevated sections were not an unqualified success. Both archeological and written evidence indicate they required extensive and frequent repairs, which entailed lengthy interruptions in the flow of water. The Aqua Claudia, which was under construction for 15 years, was repaired after 10 years of use and 9 years of disuse, repaired again 9 years later and worked on once more just four years later. Evidence of substandard construction and repair work is evident in the sections of the aqueduct that still exist. To further complicate matters, not all the water diverted into the aqueduct arrived in Rome.
The aqueduct channels were equipped with air vents or inspection holes. The channels were usually rectangular in the cross-section and varied from 0.5 to 2.0 meters inwidth and from 1.5 to 2.5 meters in depth. Sometimes two or three channels were superimposed, the upper ones being added to the original to accommodate increasing demand. Once in or near Rome, water from the aqueducts passed into large, covered catch-basins. Here waters were supposed to deposit their sediment.Waters from the catch-basins were distributed through free-flowing canals, lead pipes, and terra-cotta pipes to storage reservoirs and then through lead pipes (called fistulae) to users. The number of connections to private customers were limited; most Romans were obliged to get their supply of domestic water from public fountains.
Water was supposedly only piped into the abodes of those lucky enough to have official authorization, but having running water was so desirable that Romans were constantly bribing water officials to tap an aqueduct. In the late nineteenth century, archaeologists found a lead pipe which conveyed water from a reservoir to the Roman Forum. The pipe was 1750 meters long and required 232,750 kilograms of lead. When it is considered that there were thousands of these conduits in Rome, one can get a feeling for Rome’s massive dependence on lead. The Courses of the Nine Aqueducts in Existence at the Time of Frontinus.
As one might expect, Roman water quality standards were remedial, taking into consideration only such factors as taste, temperature, smell, and appearance. Since the quality of water from the nine aqueducts varied, the worst waters were used for articial lakes and irrigation, and the best for drinking. The aqueducts carrying water to Rome were covered to prevent the water from being contaminated by dust, dirt, and other impurities and
from being heated by the sun. The best quality waters came from the valley of the Anio River. One source (Anio Novus) from that watershed, however, did have a water quality problem every time it rained. Roman engineers first tried mixing it with water from a nearby clear spring. Next they tried running it through a small settling basin. Because of design problems with the basin, this too was unsuccessful. Finally the condition of the water was improved by carrying the head of the aqueduct higher up the valley to a reservoir formed behind an immense dam near Subiaco. The articial lake served efficiently as a settling basin and the quality of the water was improved.
The dam at Subiaco was built to form a pleasure lake for the Emperor Nero. It was a straight masonry dam and reached a maximum height of approximately 40 meters. The Subiaco Dam was the highest such structure built by the Romans and their only known use of dam technology in Italy. It failed in 1305 without leaving a trace It has been hypothesized that Rome’s dependence on lead water pipes lead to its decline. It has been suggested that the aristocracy died off from nothing more complicated than simple lead poisoning.