流域侵蚀产沙人类活动影响指数研究——以长江上游为例

The impacts of human activities on riverine sediment load: A case study of the Upper Yangtze River Basin

流域产沙是土壤侵蚀的重要反映,受降雨等自然要素和人类活动的共同作用。采用退耦理论的思想和差分方法推导出流域侵蚀产沙人类活动影响指数的简易估算方法,并对长江上游的金沙江、乌江、嘉陵江、岷江分别计算人类活动总体贡献率。结果表明,各流域人类活动对侵蚀产沙变化的贡献率达72%～97%,总体上属于抑制侵蚀的正向活动。长江上游输沙量呈阶段梯级变化,根据流域侵蚀产沙人类活动影响指数的距平累积变化的突变特征将1955～2009年划分为5个阶段并分析了每个阶段人类活动的主要特点及其对侵蚀产沙的影响。其中,20世纪80年代中期以前河流输沙量较大,主要与"一五"、"大炼钢铁"、"三线建设"、农村改革前期不稳定因素等密切相关,而70年代河流输沙量较小是受当时大搞农田基本建设和采取"挑沙面土"、"边沟背沟"等传统水土保持措施的影响,80年代中期后河流输沙量明显减少,主要受社会经济稳定有序发展、水保工程的实施及大兴水库建设等影响。

Riverine sediment load is a reflection of basin erosion influenced by both natural and anthropologic factors. Based on the conception of decoupling theory and method of difference equation, the present paper develops a simple proxy indicator representing an- thropologic impacts on the soil erosion and sediment yield. Calculations of the index for the Jinsha, Wujiang, Jialing and Minjiang rivers demonstrate positive erosion controlling effects, ranging from 72% to 97%. In the light of the stepwise sediment load changes, the paper divides 1955-2009 into five stages according to the turning points on the accumulative curve of anomaly of the index and analyses anthropologic features and their potential impacts on erosion and sediment yield. Sediment increments before the mid-1980s are due to the First Five-year Plan, the Great Leap Forward, the Great-three-line Construction and instable situation during the first several years of rural reforms. But the sediment decreases are linked to the traditional soil conservation measures, sound socio-economic development as well as construction of soil conservation projects and mushrooming of reservoirs.