目前,以水文模型提取流域水系已成为水文科学研究中的热点问题。但用DEM提取流域水系的方法不能解决流域水系唯一性的问题。故本文在没有流域纸质水系图或遥感数据的前提下,提出以DEM提取流域水系的河源最小误差法,即通过建立实际河源与提取水系河源两点之间的距离误差与网格数大小的相互关系,以两点之间误差最小为原则解决流域水系提取唯一性问题。以晋江流域为例,30m分辨率的数字高程模型(DEM)为基础数据,采用河源最小误差法提取了晋江流域水系。结果表明,最小河流长度为42m时,实际河源与提取水系河源的距离误差达到最小,相应的晋江流域的水系分维值为1.389,表明该法是提取流域水系较合理可行的算法。

With the development of hydrological model, extraction of river drainage network has been a hot topic in hydrology research. River drainage network was extracted based on topographic maps or drainage maps by digitization in the early years, but the result was influenced by data source resolution. There are presently two kinds of methods to extract river drainage network based on DEM. One is to overlay the extracted river drainage network based on DEM on the river digitalized maps which came from drainage maps or vector layer of river, to make the extract drainage network more similar to the actual river networks. But the accuracy of river drainage network depends on the resolution of drainage maps or vector layer of river. The other one is based on "inflection point" to extract river drainage network, however, the assumption of "inflection point" exists the problem of choice of scale-free interval. To solve the above problems, the river source minimum error (RSME) method was presented based on DEM in this paper. First, the relationship between the distance error of the actual river source and the extracted river network source and the size of grid was established; second, the minimum distance error was adopted as the principle to solve the problem of the uniqueness in watershed drainage network extraction, and then the river network was determined. Taking Jinjiang River as an example and using DEM with 30m resolution as data source, the RSME method was adopted to extract Jinjiang River drainage network on the platform of ArcGIS9.2. The result showed that the distance error between the river source and the extracted river network source is the smallest one when the grid numbers are up to 5814 and the minimum river length is 42m, the corresponding fractal dimension is 1.389. Moreover, the result indicated that the proposed RSME method is reasonable to extract watershed drainage network.