An aqueduct is a water system in which water is channeled through tunnels, canals, ditches, and structures guided to any place where it is needed. Ancient Rome had eleven aqueducts that were built between 312 B.C. and A.D. 226. The eleven aqueducts totaled over 260 miles in length, the longest being 59 miles. When the cities population was over a million, the distribution system used by Rome was able to provide over one cubic meter of water per day for each inhabitant: more than we use today. Although Ancient Persia, India, Egypt, and other Middle Eastern countries used aqueducts hundreds of years before Rome, the Romans are known to be the greatest aqueduct builders. Usually, when people think of an aqueduct system, arched bridges come to mind. In fact, out of the 260 miles, only 30 of them included these arches.
             For most of their length, the early aqueducts were simply channels bored through the rock, from water intake in the hills almost to the distribution cistern in Rome. The depth of the channel below ground in order to maintain a constant, very shallow flow throughout the length of the aqueduct; vertical shafts were bored at intervals to provide ventilation and access. Only in the final stretches was the conduit raised in arches to give a sufficient head for distribution of the water within the city.
             In order to keep the flow constant, the aqueducts took a roundabout route following the contours of the land and heading along spurs that lead towards Rome. As time went on Roman architects became more daring in the construction of high arches to support the flow across valleys and plains. Some of the later aqueducts were as high as 27 meters above ground level some places. Closed pipes were occasionally used to cross-valleys using the inverted siphon method: the pressure forced the water down and then up again on the other side to a level slightly lower than before. This was an expensive method because it required lead...