长江上游及西南诸河区水土流失现状与综合治理对策

Current status and comprehensive control strategies of soil erosion for the upper Yangtze and other rivers in the Southwestern China

长江上游及西南诸河区横跨我国地貌第1级台阶和第2级台阶,地形起伏显著,构造运动强烈,降雨集中,人类活动强度大,水土流失发育,侵蚀类型多样。该区水土流失的特点有:坡耕地分布广泛,侵蚀强烈,是水土流失的主要来源;泥石流、滑坡量大面广,活动频繁,威胁工程与公共安全;库区水土流失普遍发育,面源污染严重,威胁水库水质;江河源区冻融、水力、风力侵蚀交互作用,草地退化严重,降低生态功能;石漠化过程加剧,危及土地安全,导致区域贫困;工程建设规模巨大,侵蚀产沙剧烈,成为新增水土流失的重要因素。针对该区水土流失的特点,提出如下治理对策:进行以坡改梯和坡面水系建设为主的坡耕地综合整治;重点治理泥石流和滑坡,控制沟谷蚀;建设清洁小流域,综合控制面源污染;改良牧业生产方式,保护草地,修复生态;开展石漠化综合防治,抢救性保护土壤资源;加强水土保持预防监督,落实工程建设水土保持,有效减轻工程建设产生的水土流失。

There are variety of soil erosion in the upper reaches of Yangtze and other rivers in the Southwest of China, located in the transition zone from the Tibet-Qinghai Plateau to the moderate mountains and hills. Remote sensing data of 2000 indicate that the eroded area of 1 324 100 km^2, 54.34% of the total area of the region, among which 700 000 km^2 are of moderate and intense erosion; 281 200 km^2 are of extreme erosion. The main agents of erosive action include freeze-thaw erosion, water erosion, and wind erosion, which covers area 769 200 km^2, 518 000 km^2, and 36 900 km^2 respectively. Soil erosion is widely distributed on the cultivated slopes; debris flows and landslides are the most frequent disasters, threatening structures and public properties; reservoirs are polluted by non-point contaminant transported with the process of soil and water losses ; and grasslands are severely degraded in the source areas of the stream systems and the functions of ecologic barrier are largely weakened ; rocky desertification is extensively expanded as to cause the soil loss and local poverty. In addition, large-scale constructions are enhancing the soil erosion. To prevent from the further erosion, the following strategies are proposed： terracing the slopes and constructing slope water systems; controlling gully erosion and debris flows and landslides ; preventing water pollution by the integrated countermeasures of soil and water conservation; improving cultivation and protecting pasture and ecology; preventing rocky desertification and sandification; emergently preserving soil resources ; reinforcing prevention and censorship in soil and water conservation.