黄河流域河网密度的空间特征及其影响因素

河网密度是表现流域流水地貌的重要指标，研究河网密度有助于对流域整体水文地貌过程发展演化的理解。基于30 m分辨率全球数字高程模型数据，利用Archydro模块，在ArcGIS平台上提取了黄河流域花园口水文站以上的水系，并计算出河网密度，分析了黄河流域花园口水文站以上区域河网密度的空间分布，并就地貌、降雨量和植被覆盖等因素分析了自然要素对流域河网密度的影响。研究发现:（1）空间分布上，从西北向东南先增加后略微减少。西北沙漠区的河网密度非常低，高值区位于黄河中游的沙漠-黄土过渡区，再向东南又有所减小，西南区域的青藏高原由于海拔高，落差大，河网密度值也较高；（2）统计结果显示黄河流域河网密度符合正态分布，表明空间分布是多种因素综合作用的结果；（3）河网密度主要受到地貌的控制，在高差小于1 000 m和坡度<9°时，河网密度随落差和坡度增大而增大，当它们进一步增加时，河网密度有所减小。同时，河网密度的空间分布与降雨量和植被的空间分布具有一定对应性，随着降雨量和植被覆盖的增加，河网密度逐渐增加，但在超过一定的临界值后，河网密度与降雨量和植被覆盖又表现出负相关，负相关区域主要出现在东南部边缘。

Spatial Distribution and Its Influencing Factors of Drainage Density in the Yellow River Basin

The drainage density (Dd) is an important index to show the fluvial geomorphology. The study on drainage density is helpful to understand evolution of the whole hydrological and geomorphic process. Based on ASTER 30 m Global Digital Elevation Model, drainage network of the Yellow River Basin is extracted using Archydro 1.1 and Dd is calculated. The spatial characteristics of Dd of the Yellow River are described, and the relations of Dd to its influencing factors, e. g. the topography, precipitation and vegetation coverage are built. The results shows that:(1) along the direction of northeast to southwest, the Yellow River could be divided into three zones, northwest of the Loess Plateau, the main-body of the Loess Plateau, the southeast of the Loess Plateau; the northwest zone and the southeast zone are mixed with high Dd and Low Dd, and the main-body of the Loess Plateau zone is the medium Dd area; (2) there is an non-linear relation between Dd and elevation differences (ED), Dd increases with ED to a maximum, then decreases; for the maximum Dd, the corresponding ED is 500 m; (3) the non-linear relation between Dd and S is similar to that of Dd to ED, and the S which is corresponding to the maximum Dd is 9°; (4) the non-linear relations also exited between Dd to precipitation and Dd to NDVI, the corresponding values of precipitation and NDVI to the maximum of Dd are 500 mm and 0.3, respectively.