近年来，分布式水文模型与 GIS 密切结合已经成为水文预报的研究重点和热点，其中基于 DEM 提取某一流域的水流方向矩阵是其核心之一。然而在中国南方 Karst 地区具有地表和地下二元空间结构，地表有大量的洼地与漏斗和溶洞发育，如果用填洼的常规方法则改变了 Karst 地区真实栅格单元的水流方向，造成大量的平坦地区，而且提取出的水系有大量平行水系与河道的缺失。因此，利用数字化河网修正 DEM 后无需填洼就能提取出接近 Karst 地貌背景下的真实水系，提取出的水系中几乎没有平行水系和河道的缺失 , 而且正确地引导了局部栅格单元的水流流向。用该方法提取的水系对建立 Karst 地区更高精度的分布式水文模型具有很好的应用价值。

In recent years, with the rapid development and application of GIS in China, the distributed hydrological model closely integrated with GIS has become a focus and hotspot of hydrological forecasting research. To build a more accurately distributed hydrological forecasting system, one of its core problems is to extract water flow direction matrix in a river basin based on DEM. However, karst regions in south China possess a binary spatial structure of both surface and underground, where there are a lot of funnels, depressions and caverns developing on the surface. The conventional method of filling depression will change the flow direction of true grid cells in the karst regions and result in a large number of flat areas. Furthermore, there are a large number of parallel water systems and channels to be lost in the extracted water system. This thesis can provide extracting a real water system under the background of karst topography by using digital river network technology to amend DEM without filling depression. There are almost no parallel water systems and channels to be lost in the extracted river. The water system extracted with this method has a better actual value to establishing a more precisely distributed hydrological model in karst area.