海河流域产沙模数尺度效应的空间分异

Spatial patterns of scale effect of specific sediment yield in Haihe River Basin

基于流域完整性、地形的相似性,将整个海河流域分为9个分区,分析了各分区产沙模数的尺度效应。结果表明,在双对数坐标系上,产沙模数与流域面积的关系呈现出3种类型:①线性负相关,即产沙模数随流域面积的增大而减小;②无显著相关,即产沙模数随流域面积的增大基本保持不变;③线性正相关,即产沙模数随流域面积的增大而增大。从地形、分区的位置以及土地利用状况方面对所有分区产沙模数的尺度效应进行分析,并对1000 km2标准面积下产沙模数进行校正。基于校正后的数据,利用ArcGIS的Kriging空间插值法,绘制了校正后的产沙模数图。校正结果显示,流域侵蚀模数的空间分布总体表现为自西向东逐渐减小的趋势,这与流域地形的总体变化趋势是一致的。流域西部以山地为主,因而侵蚀强度大,产沙模数高;东部以平原为主,是泥沙的淤积区域,因而产沙模数低。最后,对图中产沙模数的高值区域,从气候、植被和侵蚀作用力3个方面进行了成因分析。

Building specific sediment yield map is important for planning of soil and water conservation. While the traditional method to build a specific sediment yield map usually ignored the scale effect on specific sedi- ment yield, namely, the influence of drainage area on specific sediment yield, many researches have proved there is a functional relation between specific sediment yield and drainage area. Therefore, the scale effect should be considered when building specific sediment yield. In this paper, the scale effect of specific sediment yield is studied in the Haihe River Basin. Following the principles of integrity of river basin and the similarity of topography, the Haihe River Basin is divided into 9 sub-regions. The scale effects of all sub-regionson specific sediment yield could be classified into three regional trends： （1） a flat trend; （2） a decreasing trend; （3） an in- creasing trend. Scale effect for each sub-region is explained based on location, topology, geomorphology, and land use forms. Sub-regions with fiat trends are mainly located in the areas of mountainous upper reaches and limited flood plains of lower reaches. Soil erosion is severe in mountainous area, and sediment has little chance to silt down on flood plains. Sub-regions with decreasing trends are mainly located in the areas of limited moun- tainous upper reaches and large flood plains of lower reaches, where sediment transported from mountains have more chance to silt down. There is only one sub-region with increasing trend, located in the upper reaches of the Baihe River Basin and extended from grassland with slightly soil erosion to the loess covered area with severe soil erosion. Equations are used to offset the influence of drainage area on specific sediment yield, and specific sediment yields of all hydro-stations are all calculated under a standard area. Kriging interpolation is used to cre- ate specific sediment yield maps on standard area of 1000 km2 using equation of each sub-region. The pattern of specific sediment yield map shows strong soil erosion in the west and low erosion in the east, consistent with topographic distributions of the Haihe River Basin, with mountains in the west dominated by erosion and plains in the east dominated by deposition. There are two high specific sediment yield areas. One is located in the up- per reaches of the Yongdinghe River Basin, Daqinghe River Basin, and Fuyanghe River Basin, with underlying surfacecovered by loess. The other one is located in the middle reaches of the Luanhe River Basin, expanding from loess to earth-rocky mountainous area. Those high value areas are the key areas for planning soil and water conservation.