长江上游侵蚀产沙与社会经济因子的关系

Relationship between Sediment Yield and Socio-economic Factors in the Upper Yangtze River

近年来,随着一系列水利水保工程的建设和使用,长江上游地区人类活动改变泥沙过程的作用越发明显,有必要对其地位和作用进行宏观层面的分析。以四川省和重庆市为例,利用2007年和1989年县域截面数据研究了长江上游侵蚀产沙与社会经济因子的关系,结果表明:人口密度、耕地面积与侵蚀产沙具有显著的相关性,其中人口密度与侵蚀产沙的联系更为紧密,并且存在一个临界区间,当人口密度超过这个临界,侵蚀产沙随着人口密度与耕地面积的增加而减少;反之,则侵蚀产沙随着人口密度的增加而增加。这种临界现象实质上体现了地形、降水、土壤等自然环境对产沙的影响,也有部分人为作用。从时空变化来看,人口在不断的向产沙较少、自然条件良好的地区集中,从产沙较多、不适宜生产生活的地区迁离。自然因子对东部高人口密度地区产沙影响较小,对西部低人口密度地区的影响较大。总体上,自然因子对长江上游产沙格局的影响占主导。

Taking Sichuan Province and Chongqing Municipality as an example,this paper studies the relationship between socio-economic factors and sediment yield in the Upper Yangtze River based on section data in 1989 and 2007.The results show that sediment yield is significantly correlated with population density and farmland area,in which the former appears to be more closely related to sediment yield.Moreover,in the relation of sediment yield vs.population density,a critical value of population density exists,below which the sediment yield increases with the increase of population density and over which the sediment yield increases with the decrease of population density.The phenomenon essentially reflects the influence of natural factors,such as topography,rainfall and soil property,and that of some human activities on sediment yield.Regions with higher population density than critical value are located in the east of the study area and are characterized by plains,hills and low mountains,whereas regions with lower level are located in the west and are characterized by middle and high mountains.In the eastern region,more people live on the lands with a low slope where soil erosion is slight;therefore,sediment yield is negatively related with population density.In contrast,in the western region,the population tends to be concentrated in the areas with abundant soil and water resources which usually lead to a higher intensity of natural erosion,and in turn,high-intensity agricultural practices in these areas may further strengthen local soil erosion.