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一、概况日本面积37.7万 km~2,由本州、四国、九州、北海道四个大岛和3000多个小岛组成。日本是个多山的国家,山地约占全国面积的76%,因地形陡峻,河流较短,流速较快,河水易直接入海,且水资源的补给相当一部分集中在梅雨期和台风期,水资源可利用量的时空变化较大,故有效开发利用水资源的难度也较大。日本的年平均降水量为1750mm,约为世界平均降水量的2倍。日本总水资源量平水年约4300亿 m~3,枯水年约3000亿 m~3,人
First, an overview of Japan area 377,000 km ~ 2, by Honshu, Shikoku, Kyushu, Hokkaido four large islands and more than 3000 islands. Japan is a mountainous country, with mountainous areas accounting for 76% of the country’s total area. Due to steep terrain, short rivers and fast flow rates, rivers are easily accessible to the sea. A considerable portion of water supply is concentrated in the rainy season and the typhoon period. Availability of large changes in space-time, so effective development and utilization of water resources is also more difficult. Japan’s annual average rainfall of 1750mm, about twice the world average precipitation. The total amount of water in Japan is about 430 billion m ~ 3 in normal water years and about 300 billion m ~ 3 in dry years