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1998年和1999年我国长江流域连续发生特大洪灾,究其原因,除气候条件异常外,长江中上游地区森林面积大幅度减少,使森林天然绿色水库滞洪蓄洪、涵养水源能力大为降低,致使长江上游水土流失严重,大量泥沙淤积江河,是诱发长江中下游发生洪灾的最重要原因。大量存在25°以上陡坡耕地是水土流失的主要策源地,目前重庆市25°以上坡耕地有33万多hm~2,水土流失面积为4.9万km~2,年土壤流失量1.98亿t,有60％以上来自陡坡耕地,因此解决25°以上坡耕地水土流失问
In 1998 and 1999, serious floods continued to occur in the Yangtze River valley in China. The reasons were that the forest area in the middle and upper reaches of the Yangtze River decreased significantly due to the abnormal weather conditions, which caused the detention of floodwater and floodwater in forest natural green reservoirs and greatly reduced the capacity of water conservation in the Yangtze River The serious soil erosion and water loss in the upper reaches and large amounts of sedimentation rivers are the most important causes of floods in the middle and lower reaches of the Yangtze River. A large number of cultivated lands with steep slopes above 25 ° are the main source of soil and water loss. Currently, there are more than 330,000 hm 2 of slope land above 25 ° in Chongqing, with an area of 49,000 km 2 and an annual soil loss of 198 million t and 60 More than% come from steep arable land, therefore, solve the problem of soil and water loss in arable land above 25 °