| prevent organize level provide construction dams collect |
A dam is a barrier that impounds (= takes water away) water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees (also known as dikes) are used to manage or (1) __________ water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are often used in conjunction with dams to (2) __________ clean electricity for millions of consumers. It can also be used to (3) __________ water or for storage of water which can be evenly distributed between locations.
Early dam building took place in Mesopotamia and the Middle East. Dams were used to control the water (4) __________ . Mesopotamia's weather affected the Tigris and Euphrates rivers and could be quite unpredictable.
One of the earliest (5) __________ is situated in Jawa, Jordan, 100km north-east of the capital Amman. This gravity dam featured a 9m high and 1m wide stone wall, supported by a 50m wide earth rampart (= a high wide wall of stone with a path on top, built around a castle, town, etc.). The structure is dated to 3000 BC. The Ancient Egyptian Sadd Al-Kafara at Wadi Al-Garawi, located about 25 kilometers south of Cairo, was 102m long at its base and 87m wide. The structure was built around 2800 or 2600 BC as a dam for flood control, but was destroyed by heavy rain during construction or shortly afterwards.
Roman dam construction was characterized by the Romans' ability to plan and (6) __________ engineering construction on a grand scale. Roman planners introduced a new concept of large reservoir dams which could secure a permanent water supply for urban settlements (= towns) also over the dry season. They were pioneers in the process of (7) __________ of much larger dam structures than previously built, such as the Lake Homs Dam, possibly the largest water barrier to date, and the Harbaqa Dam, both in Roman Syria. The highest Roman dam was the Subiaco Dam near Rome; its record height of 50m remained unsurpassed until its accidental destruction in 1305.
| river regulate bridges through cities prevent engineers |
Roman (8) __________ made routine use of ancient standard designs like embankment dams and masonry gravity dams. Apart from that, they displayed a high degree of inventiveness, introducing most of the other basic dam designs which had been unknown until then. These include arch-gravity dams, arch dams, buttress dams and multiple arch buttress dams, all of which were known and employed by the 2nd century AD. Roman workforces also were the first to built dam (9) __________ , such as the Bridge of Valerian in Iran.
The word ‘dam’ can be traced back to Middle English, and before that, from Middle Dutch, as seen in the names of many old (10) __________ . For example, in the Netherlands, a low-lying country, dams were often applied to block rivers in order to (11) __________ the water level and to (12) __________ the sea from entering the marsh lands. Such dams often marked the beginning of a town or city because it was easy to cross the river at such a place. This often gave rise to the name of a city or a town. For instance the Dutch capital Amsterdam (old name Amstelredam) started with a dam (13) __________ the river Amstel in the late 12th century, and Rotterdam started with a dam through the (14) __________ Rotte, a minor tributary of the Nieuwe Maas. The central square of Amsterdam, covering the original place of the 800 year old dam, still carries the name Dam Square or simply the Dam.