王菲菲

The word aqueduct comes from the Latin word for water （aqua） and the Latin word for lead （ducere）. An aqueduct leads or brings water from one location to another. Aqueducts have brought water to irrigate crops or provide fresh drinking water.

The first successful aqueducts were made in Assyria in the 800s B. C. They were several miles long. An important invention for water storage was the qanats （坎兒井） in Persia. They were underground holding places for runoff of rainwater. Tunnels led off from these large reservoirs （蓄水池） to bring water as needed to people. The flow rested on gravity where the destination was at a lower point than the source.

The Romans were the best engineers in ancient history. They mastered the art of building aqueducts. At first， a big ditch was dug. A pipe of wood， lead or clay was inserted into the ground and covered with soil. The Romans built aqueducts of many sizes throughout the Empire for drinking water as well as for the large public baths in every city or town. A typical Roman aqueduct had a gradient （坡度） of 1：4800. It would descend one foot for every 4，800 feet in length.

The Romans invented the arch （拱） which allowed them to raise the level of the aqueducts above the ground and run them at a slant from the source in the mountains to the towns. They used new products， like concrete and waterproof cement. They could manage and regulate water flow， store water in large tanks and use filters to remove sediments （沉積物） and impurities （雜質(zhì)） from the water. Aqueducts were protected by the laws so that farmers could not plow near them and possibly damage them.

The first aqueduct to serve the city of Rome was the Aqua Appia in 312 B.C. During the 100s A.D.， many new aqueducts were built across the Roman Empire. Some of the aqueducts had two or three levels of arches. Many survive today around the Mediterranean area.

In India， early aqueducts brought water to crops and for the royal bathtubs. In Petra， Jordan， engineers could bring water across mountains and through gorges to bring it to the homes and crops of the people. They also used dams to prevent flooding. In Peru， around 550 A. D.， a system of aqueducts was made of stones placed by hand in a certain way. The Guyabo National Monument in Costa Rica contains a system of aqueducts still being used. It is made of rounded river stones.

In Sri Lanka， a large canal connected two reservoirs on a slope. Because the civilization disappeared in the 1200s， there is no evidence of the method used to make these exact measurements. Evidence of an irrigation system has been found in Mexico dating from 700 B. C. People built a dam to control water and guide it to crops. Around 400 A. D.， an aqueduct was built in the same area.

The Potomac Aqueduct was built in Washington， D. C. in 1830. It extends over the Potomac River connecting northern Virginia with Georgetown in the capital. The largest aqueducts in the world have been built in the United States in modern times. The Colorado River Aqueduct brings enough water to provide the city of Los Angeles with water. The largest and most costly in the United States is the Central Arizona Project. It runs 336 miles from Parker， Arizona， to the cities of Phoenix and Tucson.

In Spain， a system of aqueducts was built in 1979. It carries water 178 miles from north to south. The Yangtze Basin is connected to Beijing by three separate systems. It is called the? ?South-North? ?Water? ?Transfer? Project.

Modern aqueducts may use a system of pipelines which can carry water long distances.

Answer the following questions.

1. Where were the first successful aqueducts built in the 800s B. C.？

2. What was invented by the Romans according to the passage？

3. What was the name of the first aqueduct to bring water to Rome in 312 B. C.？

4. Where the Guyabo National Monument located？

5. When was the Potomac Aqueduct built in Washington， D. C.？

6. Where is the North-South Water Transfer Project located？