Aqueduct

The ancient Assyrians built artificial channels called aqueducts to bring water to their towns. One of them was built in 691, carrying water for 50 miles to Ninevah, capital of the ancient Assyrian Empire.

The Romans built thousands of miles of aqueducts to bring water to their towns. Many of these were elevated iron, stone or wood structures, and were marvels of engineering. Eight aqueducts with a combined length of over 200 miles supplied Rome itself.

The Aqua Marcian in Rome, about 90 kilometres (about 56 mi) long and built by the praetor Marcius in 144 BC, was the first Roman aqueduct to carry water above ground, the bridged section being about 16 kilometres (about 10 mi) long.

The Aqua Marcia used a series of arches and tunnels to transport water from a spring near Lake Bracciano to Rome. The aqueduct is 51 feet high at its highest point, and it travels 31 miles. This means that the water had to be able to flow downhill at a rate of 1 inch per 1,500 feet.

The Romans were able to achieve this feat by using a series of techniques that are still used today in aqueduct design. They used a combination of arches and tunnels to create a gradual slope for the water to flow down. They also used a type of concrete called hydraulic concrete, which is made with volcanic ash and lime. Hydraulic concrete is strong and water-resistant, making it ideal for use in aqueducts.

Nine aqueducts were built in all, providing Rome with some 143,845 cu m (38 million gal) of water each day. 

The largest Roman aqueduct, at Carthage in Tunisia, was 140 kilometres (87 mi) long and was built during the reign of Publius Aelius Hadrianus between 117 and 138.

Many Roman aqueducts are still standing, such as the one carried by the Pont du Gard at Nîmes in southern France, which was built about 8 BC. It is over 50 kilometres (31 mi) long and the whole aqueduct descends in height by only 12.6 m (41 ft) over its entire length. The aqueduct formerly carried an estimated 40,000 m3 of water a day to the fountains, baths and homes of Nîmes.

By Benh LIEU SONG (Flickr) - Pont du Gard, 

In modern times, several extensive aqueducts have been built in Europe. The Marseille aqueduct, completed in 1847, is 97 km (60 mi) long; the second Kaiser Franz Joseph aqueduct, in Vienna, is 232 km (144 mi) long.

The Barton Swing Aqueduct is a moveable navigable aqueduct in north west England, which carries the Bridgewater Canal across the Manchester Ship Canal. The swinging action allows large vessels using the ship canal to pass underneath and smaller craft, both narrow boats and broad-beam barges to cross over the top. The aqueduct, which opened in 1894, is the first and only swing aqueduct in the world.

Wales' Pontcysyllte Aqueduct opened on November 26, 1805. The 18-arched stone and cast iron structure is for use by narrow boats and took ten years to design and build. It is the highest navigable aqueduct in the world and has been made a UNESCO World Heritage Site.

In modern times, the largest aqueducts of all have been built in the United States to supply the country's biggest cities. The largest and most expensive is the Central Arizona Project, the largest and most expensive aqueduct constructed in the US. It stretches 336 miles from its source near Parker, Arizona to the metropolitan areas of Phoenix and Tucson.

After a 5 year, 238-mile (383 km) long construction project to build the Los Angeles Aqueduct, at the ceremony for the arrival of the first water at the end of the aqueduct on November 5, 1913, Chief Engineer William Mulholland's speech was nothing more than the words: "There it is. Take it." 

The Delaware Aqueduct is an aqueduct in the New York City water supply system. It normally carries 3,028,320 cu m (800 million gal) of water daily from the Catskill Mountains to New York. At 13.5 feet (4.1 m) wide and 85 miles (137 km) long, the Delaware Aqueduct is the world's longest tunnel.

The Delaware Aqueduct provides half of New York City's fresh water, but has been leaking up to 35 million gallons of water per day since at least the 1990s.

Sources Funk & Wagnells Encyclopedia,  Hutchinson Encyclopedia