ダム1（英: Dam） - 雲心月性...

Dams, sometimes called embankments, serve various purposes including hydroelectric power generation, flood control, irrigation, forestry management, erosion control, and waste disposal.

Typically constructed with materials like concrete, earth, and rocks, these structures span rivers, valleys, or enclose depressions. Large dams often create reservoirs upstream. Natural dams can also form when landslides or debris flows block rivers.

Additionally, there are underground dams that block subterranean water flow. The term 'dam' is also used metaphorically to describe storage or retention, as in 'green dam,' which refers to the water retention capability of forests.

When the purpose is water intake or level regulation, dams are called weirs, excluding erosion control embankments. Beavers are well-known for constructing dams.

For more information on dams in Japan, please see 'Dams in Japan.'

発電出力が世界第1位の三峡ダム

Etymology

The word 'dam' has been used in English since Middle English, likely derived from the Middle Dutch word 'dam.' In the Netherlands, with its many low-lying areas by the North Sea, dams and dikes were frequently built to regulate river water levels and prevent seawater intrusion.

The construction of dams often facilitated river crossings, leading to the formation of cities. For example, Amsterdam and Rotterdam were established where dams were built on the Amstel and Rotte rivers, respectively.

貯水量が世界第1位のカリバダム

Overview

The definition of dams varies by country, but according to the International Commission on Large Dams, established in 1928 and now comprising 88 member countries, a dam is defined as an embankment with a height of 5.0 meters or more and a storage capacity of 3 million cubic meters or more.

Dams over 15 meters in height are referred to as high dams, while those below this height are called low dams.

In Japanese river law, only high dams are recognized as 'dams,' while other embankments, even if called dams, are treated as weirs.

Historically, before clear definitions were established, embankments attached to mountains or actively controlling water flow were classified as dams, whereas those attached to dikes or passively controlling water flow were classified as weirs.

As structures for flood control and flow maintenance were built among weirs, the distinction between dams and weirs blurred, necessitating precise definitions. When viewing a dam from upstream, the right side is called the right bank, the left side is the left bank, and the downstream face is referred to as the back face.

堤高が世界第2位のヌレークダム

The purposes for dam construction are varied.

Major purposes include flood control (flood regulation and unspecified water use) and water utilization (supplying irrigation water, drinking water, industrial water, snow-melting water, hydroelectric power, recreation, etc.).

Dams for flood control are called flood control dams, and those for water utilization are called water utilization dams.

Dams serving multiple water utilization purposes or both flood control and water utilization are called multi-purpose dams.

Additionally, dams for forestry management, erosion control embankments, tailing dams for mining, and dams for waste disposal are treated separately from dams defined by river law.

This section describes high dams, defined by the International Commission on Large Dams and adopted in the standards of Japanese river law and the River Management Facilities Ordinance, as those with a height of 15.0 meters or more.

For information on weirs, forestry management dams, erosion control embankments, tailing dams, natural dams, and subterranean dams, please refer to their respective sections.

In Japanese, dams are counted using the unit 'ki,' so they are referred to as '1 ki.'

As of 2011, China holds the distinction of having the largest number of dams in the world, with a total of 87,000."

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