GIS环境下基于DEM的中国流域自动提取方法

应用地理信息系统平台，建立基于水文站网和水资源信息的空间化水循环数据库是研制开发全国水循环信息管理系统的关键和基础，为了与全国水文站网的观测资料相匹配，水循环数据库的结构将按流域组织，因此快速、有效地自动提取全国流域是所有工作进展的前提。为了从数字高程数据中自动提取全国流域，以提高基于GIS的全国水资源信息获取的效率，从DEM的特性出发，提出了一种从DEM中自动提取全国流域的实用方法。该方法利用1：25万DEM数据，首先将全国流域划分为14大流域片，并在每一流域片内分别提取流域。提取过程如下：首先对DEM数据进行填洼和削峰，然后确定每个栅格单元的水流方向，再根据各栅格单元的水流方向，计算出每个栅格单元的汇流能力，根据汇流能力采用阈值法确定河流网络，最后通过河流网络和流域出水口，快速识别出所有子流域。另外，还给出了利用GIS软件ARC/INFO GRID提取全国流域的AML程序代码，并以海河流域作为实验区将抽样测量结果和自动提取结果进行了实验对比分析，其结果表明利用该方法提取的流域数据与利用手工方法绘制的流域基本一致，证明该方法是有效的。

AUTOMATED EXTRACTION OF DRAINAGES IN CHINA BASED ON DEM IN GIS ENVIRONMENT

It is an important key and foundation to set up a database of spatial water cycle based on GIS technology for developing water cycle information system. In order to match the observation data, the structure of database will be organized according to drainages. So automated extraction of the flow network and drainages is a premise of all other works. This paper puts forward a method that automatically extracts drainages in China from DEM data. This method used DEM data of 1∶250,000 scale, and firstly divided the DEM of whole country into 14 parts based on the drainages extracted from 1 km DEM data; secondly filled sinks and removed peaks in each part; thirdly identified the flow direction of each cell using flowdirection () function; fourthly calculated the flow accumulation of each cell according to flow direction and identified the flow network by setting the threshold value; finally used the watershed() function to find out all the sub drainages based on the flow networks and the watershed outlet. On the other hand, this article listed the AML code for automated extraction drainages from DEM data. Finally the authors checked the result of automated extraction using some surveyed data in Haihe drainage area. Through analysis on the comparison between the flow networks and drainage area that extracted using this method and surveyed data, it is concluded that this method is effective and efficient.