将推荐的水系划分与河流分级Horton法相结合,通过合理选取最小河流(流域)单元、科学制作河流树状图表,初步研究了长江流域(不含太湖水系)的河流分级。研究结果显示:①推荐将长江水系划分为干流水系与雅砻江、岷江、嘉陵江、乌江、洞庭湖、汉江、鄱阳湖、太湖8个支流水系;② 581条河流基本特性资料的收集、整理与分析表明长江流域河流的河长与流域面积约为0.5次方关系,选取流域面积不小于2 000 km²或河长不小于100 km的河流为最小河流(流域)单元,确定长江流域(不含太湖水系)河流总数为374条;③以岷江水系为例,精心制作了长江流域各水系的河流树状图表,树状图显示了河流隶属关系、分级数、河长、流域面积等特性;④长江流域(不含太湖水系)最高河流分级数为6级。按河流统计:6级1条(0.3%),5级3条(0.8%),4级6条(1.6%),3级14条(3.7%),2级71条(19.0%),1级279条(74.6%);按水系统计:岷江、嘉陵江、鄱阳湖为5级,干流、雅砻江、洞庭湖、汉江为4级,乌江为3级。

According to the recommended watershed division and by means of the Horton method, we preliminarily researched the stream order classification of the Yangtze River (exclusive of the Taihu Lake watershed sub-basin) by properly choosing the minimum stream. Tree diagrams and tables were obtained. Results show that (1) The Yangtze River is recommended to be divided into main channel watershed basin and 8 tributary watershed sub-basins inclusive of Yalong River, Minjiang River, Jialing River, Wujiang River, Dongting Lake, Hanjiang River, Poyang Lake and Taihu Lake. (2) Statistic and regressive analysis of 581 streams of the Yangtze River shows that stream length is about 0.5 power related to watershed area. Streams with watershed area no less than 2 000km² or stream length no shorter than 100km are selected as the minimum stream. Thereupon based on the minimum stream, the total number of streams of the Yangtze River is determined to be 374. (3) With Minjiang River watershed sub-basin as an example, tree diagrams and tables of streams for all watershed sub-basins of the Yangtze River are elaborately fabricated. The diagrams and tables illustrate the basic information such as river kinship and affiliation, stream order, basin area, and river length. (4) The highest stream order of the Yangtze River is the 6^th order. In regard to streams, there are 1 or 0.3% 6^th-order stream, 3 or 0.8% 5^th-order streams, 6 or 1.6% 4^th-order streams, 14 or 3.7% 3^rd-order streams and 71 or 19.0% 2^nd-order streams and 279 or 74.6% 1^st-order streams; while in terms of watershed division, sub-basins of Minjiang River, Jialing River and Poyang Lake belong to 5^th-order stream, sub-basins of main channel, Yalong River, Dongting Lake and Hanjiang River belong to 4^th-order stream, and Wujiang River sub-basin belongs to 3^rd-order stream.