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如果说金字塔是埃及古文明的象征,那么位于尼罗河三 角洲的那占地数万平方英里的水利灌溉系统则是现代文明的体现。这个系统无论是规模还是效益,都是世界一流的。 然而,居住在那里的约六千万居民却已发现过于有效的水利系统给他们带来了严重的生态学问题,三角洲中河水滞流,泥沙淤积。过去,三角洲的冲积平原一直在增加,现在,某些地区的海岸线反而开始回缩,严重之处有百米之多。更糟糕的是,受碱化侵蚀,土地的应用率正在日益下降。 研究者们把土地的受侵蚀归因于开罗南部阿斯旺水坝的建立,认为它阻止了水流及淤泥进入地中海。但是,美国史密森学会的海洋学专家丹尼尔·斯坦利经多年的实地调查,新近在《海运地理》上提出了另一个极其简单却又令人信服的解释,即整个系统中长达上万公里的人工运河是导致三角洲土壤侵蚀的主要原因。正是因为这些纵横交错的运河,使
If the pyramid is a symbol of Egypt’s ancient civilizations, the water-irrigation system in the Nile Delta, which occupies tens of thousands of square miles, is a manifestation of modern civilization. This system is world-class in terms of both size and effectiveness. However, about 60 million residents living there have found that overly effective water systems have posed serious ecological problems for them. River water in the delta is stagnant and silting sediments. In the past, the alluvial plain in the delta has been increasing. Now, in some areas, the coastline has started to reverse instead of being as serious as a hundred meters. Worse, the use of land is declining due to alkalization. Researchers attributed the erosion of the land to the establishment of the Aswan dam in southern Cairo, in the belief that it prevented water and silt from entering the Mediterranean Sea. However, Daniel Stanley, an oceanographer from the Smithsonian Institution in the United States, has come up with another extremely simple yet convincing explanation of “maritime geography” after many years of field investigation. That is, tens of thousands of the entire system The kilometers of man-made canals are the main cause of soil erosion in the delta. It is because of these criss-crossing canals