长江流域水系划分与河流分级初步研究
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长江流域水系划分与河流分级初步研究
董耀华汪秀丽
摘要: 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。
关键词: 长江; 水系划分; 河流分级; Horton 法; 最小河流(流域) 单元; 河流树状图表
中图分类号: TV212 文献标志码: A 文章编号: 1001-5485(2013) 10-0001-05
Preliminary Research on Watershed Division and Stream Order Classification of the Yangtze River
DONG Yao-hua1,WANG Xiu-li2
Abstract: 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 6th order.In regard to streams,there are 1 or 0.3% 6th-order stream,3 or 0.8% 5th-order streams,6 or 1.6% 4th-order
streams,14 or 3.7% 3rd-order streams and 71 or 19.0% 2nd-order streams and 279 or 74.6% 1st-order streams; while in terms of watershed division,sub-basins of Minjiang River,Jialing River and Poyang Lake belong to 5th-order stream,sub-basins of main channel,Yalong River,Dongting Lake and Hanjiang River belong to 4th-order stream,and Wujiang River sub-basin belongs to 3rd-order stream.
Key words: Yangtze River; watershed division; stream order classification,Horton method; minimum stream; tree diagram and table of stream
1 研究背景
长江流域水系与江湖关系复杂[1],目前通常按水系进行划分; 各种水系划分方法虽略有差异,但基本上都是围绕长江干流及主要支流或湖泊进行区划(图1) 。这种“自大河而小河”的水系划分方法比较符合长江流域水系(支流或湖泊) 相对独立的特性,有利于流域管理和河流治理规划、科研与设计;但同时也存在着河流划分方法与研究上的缺陷:①水系划分存在一定任意性; ②无法确定各划分水系及长江流域总体的河流分级数; ③难以进行长江与其它大江大河之间河流分级与特性差异的对比研究。
河床演变学[2]通常采用的是“自小河而大河”的河流分级法,通过最小河流单元的合理选取,可以使河流分级“标准化”,减少任意性,进而也便于区别和比较不同流域或不同水系的河流分级数与大小。
本文研究思路是: 首先在总结已有水系划分方法基础上,提出长江流域水系的推荐划分; 然后基于河流分级Horton 法,借助最小河流(流域) 单元的合理选取和各划分水系河流树状图表的科学制作,初步研究长江流域(不含太湖水系) 的河流分级。鉴于太湖水系河网复杂及人工运河影响,研究暂不含太湖水系并不会影响长江流域的总体分级和其它水系河流分级结果。
2 长江流域水系划分
2.1 水系划分现状