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长江流域面积180万平方万里,大部分处于亚热带区域,雨量多,气温高,日照充足,历来是我国工农业经济的重要地区。目前有耕地3.7亿亩,人口3.5亿人,粮食棉花等主要农作物产量占全国的36～40％。但是,由于历代人口发展,造成过量的垦殖和砍伐,致使水土流失不断加重。据记载:长江口入海泥沙自宋代以来即不断增加;近几十年来,河口泥沙平均年达4.5亿吨,而更大的部分则堆积在各山丘的小区域内。因此,长江流域对水土保持工作无疑应予以高度重视。 长江流域大的地貌单元,自西而东为青藏高原,横断山脉,云贵高原,四川盆地,鄂西山地,中下游丘陵区,中下游平原区。
The Yangtze River basin covers an area of 1.8 million square miles, most of which are in the subtropical region. Rainfall, high temperatures and abundant sunshine have always been an important area for China’s industrial and agricultural economy. At present, there are 370 million mu of arable land and a population of 350 million people. The output of major crops such as grain and cotton accounts for 36-40% of the country’s total. However, due to the development of population in previous years, excessive reclamation and deforestation have led to increasing soil and water loss. It is recorded that the sediment entering the Yangtze River Estuary has been increasing since Song Dynasty. In recent decades, the sediment of the estuary averaged 450 million tons per year, while the larger part accumulated in the small area of each hill. Therefore, the work of soil and water conservation in the Yangtze River valley undoubtedly should attach great importance. The major geomorphic units in the Yangtze River basin are the Tibetan Plateau, the Hengduan Mountains, the Yunnan-Guizhou Plateau, the Sichuan Basin, the western Hubei Mountains, the hilly areas in the middle and lower reaches, and the plain areas in the middle and lower reaches from the west to the east.