黄河中游地区流域产沙中的地貌临界现象  

Thresholds in Variation of Sediment Yield in the Middle Yellow River Basin

作　　者：卢金发[1] 黄秀华[2] 

机构地区：[1]中国科学院地理科学与资源研究所,北京100010 [2]中国科学院遥感应用研究所,北京100101

出　　处：《山地学报》2004年第2期147-153,共7页Mountain Research

基　　金：国家自然科学基金资助项目(编号40171013);国家自然科学基金委员会和水利部联合资助重大项目(编号59890200);中国科学院地理科学与资源研究所创新项目(编号CXIOG-A02-01)~~

摘　　要：地貌现象的演化常常存在着由量变到质变的临界条件。地貌临界是地貌学研究的重要理论问题之一。本文利用黄河中游地区近60个水文测站资料,探讨了流域产沙量随降雨、植被和流域面积变化过程中的地貌临界现象。结果表明,流域产沙量与年降雨量之间关系遵循Langbein-Schumm曲线,最大产沙量大致出现在年降雨量400mm吼左右的半干旱草原区,即无定河以北的皇甫川、孤山川、佳芦河流域。同时,由沙黄土、砒砂岩流域向基岩山地流域过渡,流域产沙量峰值趋于减小,而峰值出现所需要的降雨量渐趋增大,显示出不同自然地理地带和地域最大产沙区位置和产沙强度的不同。流域产沙量与植被之间呈现为相当好的非线性负相关关系。流域产沙量随植被变化存在着二个临界值,一是当流域植被覆盖度等于30％时,另一是当植被覆盖度等于70％时。这一现象以往只是在试验小区或试验流域见到,本研究表明,类似的现象在天然河流流域也存在。受流域上下游不同生物气候及下垫面特性的控制,流域产沙量随流域面积的增大呈现出复杂多样的变化,可以是增加,也可以是减少。然而,对于大多数复合流域来说,随着流域面积的增大,流域产沙量一开始趋于增加,当流域面积接近1 000 km2左右时,流域产沙量达到最大,而当流域超过1 000 km2以后,流域产沙量反而趋于?Thresholds are commonly observed when a dramatic change takes place in geomorphic development. Since 1970' s geomorphic thresholds have become one of important academic themes in geomorphology and attracted wide attention from various aspects. Nearly 60 river basins with areas ranging from 500 to 2 500 km2 were chosen for an investigation on geomorphic thresholds in variation of sediment yield with basin characteristics in the Middle Yellow River. It was shown that variation of sediment yield with annual average rainfall follows Langbein-Schumm law in the Middle Yellow River. The peak sediment yield occurs in semi-arid steppe zone where annual average rainfall reaches about 400 mm, but a decrease of peak sediment yield and an increase of rainfall threshold were observed due to joint effect of rainfall, surface material, vegetation coverage and basin morphology when it transits from the basins of sandy loess and heavily weathered siltstone and mudstone to those of hard rock. A non-linear negative relationship exists between sediment yield and vegetation coverage. Two thresholds can be observed as sediment yield changes with vegetation coverage. Sediment yield increases markedly once vegetation coverage decreases across 70% , and a dramatic increases of sediment yield can been seen when vegetation coverage of 30% is crossed. It is interesting that this phenomenon could be seen before only in experimental plots and watershed, but this paper suggests that similar relations exist in natural river basins. Both downstream decrease and increase of specific sediment yield were observed in main tributary basins of the Middle Yellow River. More detailed analysis indicates that bio-climatic and morphologic features are the primary factors that exert most important control on the relationship between specific sediment yield and basin area. Landforrn type in different stages of evolution is another important factor affecting the relationship. When assembling together sediment yield data from various environments more complicat

关 键 词：黄河中游 泥沙产生 地貌临界 

分 类 号：S157.1[农业科学—土壤学]