长江经济带1:25万三级流域分区内水系分布数据集（2012年）

本数据集在国家基础地理信息中心全国1:25万地形数据库基础上，提取水系数据，根据《中国河流名称代码》（SL 249-2012）进行梳理，可对全国4级流域（水系）以上主干河流及其支流进行编码，参考《中国河湖大典》补全7级以上河流，并对照遥感卫星影像确定河流走向。
数据集包含1个shp矢量文件，为线层矢量数据，cj25水系.shp。该数据的特点为：每条河流在空间上都是完整的要素，每条河流源头进行了核定，河流流向明确；结合子流域特征，按照河流长度大小，对其主干支流进行了划分，河网层次明确。

This dataset is derived from the National 1:250,000 Topographic Database of the National Geomatics Center of China, by extracting hydrological data and standardizing it in accordance with *Code for Chinese River Names* (SL 249-2012). It supports encoding of main streams and their tributaries at or above the 4th-order watershed (hydrological system) across the entire country. Rivers with a rank of 7th-order or higher are supplemented with reference to *Chinese Rivers and Lakes Encyclopedia*, and the flow direction of each river is confirmed via comparison with remote sensing satellite imagery.

The dataset contains one shapefile vector file, which is line-layer vector data, named cj25水系.shp. The characteristics of this dataset are as follows: Each river is a complete spatial feature; the source of every river has been verified, and its flow direction is clearly defined. Combined with sub-watershed characteristics, main streams and their tributaries are classified based on river length, resulting in a clearly defined hierarchy of the river network.