Knowledge Resource Center for Ecological Environment in Arid Area
| 塔里木河干流古河道变迁研究 | |
| 其他题名 | Study on palaeochannels migration along the main stream of Tarim River |
| 李开封 | |
| 出版年 | 2011 |
| 学位类型 | 硕士 |
| 导师 | 穆桂金 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 塔里木河流域地表物质松散，颗粒较细，且流域降水集中在夏季，多暴雨，河流汛期冲淤变化剧烈，极易迁徙改道。河流改道会直接导致决堤等水害灾难的发生以及水资源的大量耗损，且影响着沿河聚落分布、居民正常生产生活以及荒漠河岸林生态系统的空间分布与演替，并造成河道两岸弃置土地的盐渍化和荒漠化等生态环境问题的出现。在地质历史时期塔里木河南北迁移改道频繁，在塔里木河干流南北两岸80~120km范围地表遗留一系列古河道。前人仅涉及对这些古河道的遥感调查以及自清以来河道迁移变化的研究上，对其具体形成时代及河道迁移原因并没有进行深入研究探讨。因此对塔里木河古河道进行系统研究十分必要。本文通过对塔里木河干流南北岸古河道表层沉积采样，对其进行沉积特征及时空变化关系研究，探讨河道存在晚期沉积环境特征，梳理其随时间发生的迁移变化，并总结归纳古河道迁移影响因素。研究结果显示：\n(1)塔里木河古河道表层沉积物粒度较洪泛平原细小，反映古河道存在晚期水动力较弱。而且部分古河道表层沉积中，河相沉积物中含风成沙夹层，反映这些古河道存在晚期河流有长时段断流，沉积环境受风水两相相互作用。\n(2)塔里木河干流在1438~ 1696 AD之间曾发生过大规模南北迁移，该时期处在气候小冰期(1400~1920 AD)的早中期，即在小冰期的早中期塔里木河干流河道南北摆动范围为A、B、C三片古河道区。\n(3)塔里木河干流南北两岸古河道最后干涸时期在时空变化上具有不同特点：北岸古河道(B、C区)具有自北向南的迁移趋势，且两区域古河道所处时代相同。而南岸诸多古河道(A区)可能存在多支并流或串流现象，且南岸古河道最后存在时代要晚于北岸古河道。\n(4)小冰期气候改善，周边山区降水增多，汇入塔里木河流量增大，致使塔里木河干流水动力条件增强，再加上塔里木河流域特殊的地面物质组成，造成塔里木河极易迁徙改道。此外，河流顶托以及地貌因素在该时期河流流向及河道迁徙方面也起到重要作用。\n 地质历史上塔里木河迁徙改道频繁，在小冰期时塔里木河干流摆动幅度达80~120km，涉及A、B、C三片古河道区。近现代以来人为活动对塔里木河水文特征、流域植被等自然要素的作用强度持续增大，特别是现代以来，影响作用愈发显著。塔里木河在今后发展过程中仍将继续演变，但当代大量的河水散失在中游，且渗漏、蒸发损耗严重，因水量的减少，下游断流长度的不断增加，当前和今后河道的变迁动力主要源自于河道淤积，除局部河势变化较大外，将来在自然条件没有巨大突变情况下塔里木河河道整体在长期趋势上仍将相对稳定。 |
| 英文摘要 | Surface sediments in the watershed of Tarim River are loose soils, particle size of them are very small. In Tarim Basin, precipitation is uneven on seasonal ditribution, mostly con-\ncentrating in the summer months, and there are also many torrential rains in this season. All of these cause dramatic changes of rever erosion and deposition in flood season, and finally resulting in the esay channel diversion of Tarim River. River diversion directly brings about lots of water waste and many water disasters, such as levee failure, and affects coastal settlements distribution, residents normal life, the succession of riparian forest ecosystem. To some extent, It also creates many ecological environment problems, such as making littoralland desertification and salinization. In the geological period, Tarim River had migrated along current main stream about 80~120 kilometers from south to north and generated many palaeochannels. Predecessors had identified the space distribution of palaeochannels along current main stream of Tarim River using remote sensing satellite image, and researched river channel migration of partial palaeochannes since Qing dynasty, but they did not pay close attention to the rest part of palaeochannels formed before Qing dyansty. So it is very necessary to date precisely all of the palaeochannels along the main stream of Tarim River. By means of determining the age of palaeochannes, particle size analysis in surface sediments of palaeochannels, we get some discoveries for the first time. The results indicate that:\n (1) Prticle size of surface sediments in palaeochannels is small, it suggests that the hydro-\ndynamic force was very weak at the late exitence stage of palaeochannels. And in some palaeochannels, there are sandstorm within the surface sediments, it shows that there is a period of river draught-up, and the sedimentary environments are influcenced concurrently by wind effect and hydraulic role.\n (2) Among 1438~1696 AD, which is the early and middle period in the Little Ice Age (1400~1920 AD), river channel of Tarim River had migrated seriously. So in this period Tarim River had migrated in the districts of A, B and C.\n (3) The last dry-up ages of all palaeochannels along the main stream of Tarim River has different time-space distribution characteristics: in the distrcts of B and C, they have the same era of existence, and the palaeochannesl had migrated from north to south; but in A district, all the ages of palaeochannels are posterior to the ones in districts of B and C. In addition, some palaeochannels had the same age in district A, so these palaeochannels had existed synchronously at some time in 17th Century.\n (4) During the Little Ice Age, precipitation had increased in mountainous area around the Tarim Basin, climatic conditons was better in the watershed of Tarim Basin. Then the amount of flow increased in Tarim River, water power boosted, and the quantity of silt in Tarim River increased, so it was very esay for Tarim River to divert. Except the factors above, the distribution charactiscic of river system and landform in Tarim Basin had also played very important roles for the migration of Tarim River at this period.\n In the geological history, Tarim River had swung north-south drastically along the current main stream of the river. In the Little Ice Age (about 1400~1920 AD), the river had migrated 80~120 kilometers from south to north, covering the distribution districts of palaeochannels of A, B and C. But in modern and contemporary times, human activities had remarkably influenced many natural elements in the watershed, such as hydrologic conditions and vegetation cover. So Tarim River will evolved in the future, but because of lots of river flow losing in desert within middle reaches, and the length of draught-up of river in lower reaches is increasing, the watercourse of Tarim River will be relatively stable, except partial changes of the river channel in a short time. |
| 中文关键词 | 塔里木河 ; 古河道变迁 ; 小冰期 |
| 英文关键词 | Tarim River Palaeochannels migration Little Ice Age (LIA) |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院新疆生态与地理研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287005 |
| 推荐引用方式 GB/T 7714 | 李开封. 塔里木河干流古河道变迁研究[D]. 中国科学院大学,2011. |
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