Knowledge Resource Center for Ecological Environment in Arid Area
| 雅鲁藏布江流域水体稳定同位素时空变化及其水文循环意义 | |
| 其他题名 | Spatial and temporal variability of the stable isotopic composition in waters and implications for water cycle in the Yarlung Zangbo River basin |
| 任伟 | |
| 出版年 | 2014 |
| 学位类型 | 博士 |
| 导师 | 姚檀栋 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 青藏高原被称为“亚洲水塔”，是亚洲多条大河的发源地，为了准确评估全球变化对青藏高原水资源的影响，需要对这些地区不同尺度的水文循环特征有全面系统的认识。雅鲁藏布江是世界上海拔最高、人类活动影响最小的一条大河。该流域内具有独特的地形、气候和水文特征：流域内垂直高差大、受季风与西风共同作用、降水和径流季节变化极为显著、具有从湿润到干旱多种气候类型，这些特征为开展同位素水文研究提供了有利条件。本文以雅鲁藏布江流域内的河水为主要研究对象，通过定点采样与加密采样的方式采集样品，进行了河水同位素时空变化的分析和讨论，明确了其与区域气候、地形和降水之间的关系，建立了流域不同尺度的河水d18O-dD关系线，最后对典型地区进行了水循环综合研究。主要研究结果如下： 1. 揭示了流域内河水同位素空间变化及其影响因素。流域内河水中d18O和d-excess从西往东整体先降低再升高的趋势，且东部河水d18O存在显著的“高程效应”，表明了流域东部和中部以季风为主导，季风水汽分别通过藏东南水汽通道和翻越喜马拉雅山到达这两个地区，而流域西部则受西风和印度季风共同作用。在流域内部，受局地水循环影响，河水同位素空间变化也表现出一些显著特征：在流域东部，综合春夏季河水的d18O垂直递减率为0.34‰/100 m，该地区垂直递减率受季风降水、冰川融水和春季降水共同影响；流域中部位于雨影区，由于喜马拉雅山南北坡降水季节分配的区域差异，随着靠近喜马拉雅山，河水d-excess显著升高。另外，由于流域内气候显著的东西向差异，从东部的湿润区到中部的干旱区，河水d18O-?D线逐渐偏离全球大气水线，与区域蒸发作用以及河水对季风降水依赖逐渐增强相对应。 2. 明晰了流域内大河河水同位素季节变化与补给来源的关系。流域内各河流河水d18O反映出相似的季节变化：从春季开始河水d18O逐渐升高，最高值出现于6月左右，之后逐渐降低，最低值出现于8～9月，这种变化与流域内降水d18O季节变化较为一致，说明降水是流域内河水的最主要补给来源。流域内各河流基流以低的d-excess为特征，河水d-excess总体上从春季开始逐渐升高，夏季为高值，从最高值出现的时间看，东部地区早于其他地区（分别为6月左右和8～9月），是各地区河水中基流、春季降水、冰川融水和季风降水相对比例变化的直接体现。 3. 阐明了流域内河水同位素与降水同位素之间的关系。由于河水主要来自于上游高海拔地区，河水d18O一般低于当地降水d18O，且越往下游二者的相关性越弱，但年楚河河水表现出了相反的特征，主要与该流域内强烈的人类活动影响下径流减少以及水体多次循环使用导致水体进一步产生强烈蒸发有关。由于大河流域对水体的较强调节能力以及上下游径流的继承关系，大河河水d18O随地理要素（海拔和经度）的变化率远小于流域内的降水d18O。季节变化上，降水d18O与海拔和经度的线性关系只存在于7～9月的季风期，而河水?18O则存在于5～9月，流域内由东往西逐渐减少的春季降水极可能是造成这种差异的主要原因。另外，除了流域东部地区外，其他地区河水d18O-dD关系线都明显偏离当地降水d18O-dD关系线，反映了蒸发作用的重要影响。 4. 基于稳定同位素方法，结合实测水文气象资料，对拉萨河流域水量平衡进行了估算。结果表明：2009～2011年拉萨河流域出山口径流占流域总降水量的36%，地表水体及土壤水分的蒸发量与植被的蒸腾量约占流域总降水量的20%和44%。 |
| 英文摘要 | The Tibetan plateau, where nearly all major rivers in Asia are fed from, is the water tower of Asia. In order to effectively evaluate the impact of climate change on water resources in the Tibetan Plateau, it is necessary to get a comprehensive cognition to the water cycle on different temporal and spatial scales. The Yarlung Zangbo is the highest major river in the world where humans have had a minimal impact. The Yarlung Zangbo River basin is also characteristic of distinct hydrologic processes due to unique hydroclimatic background: large regional altitude difference, influences of the westerlies and Indian summer monsoon, pronounced seasonality in precipitation and river discharge and various regional climate. This basin thus provides ideal conditions for investigating the isotopic hydrolgocial processes. This study first analyzed spatial and temporal variability of river water isotopes (?18O and ?D) to determine their relationship with regional climate, terrain and precipitation. And then, the meteoric water lines and river water lines were established on various spatial scales. Finally, comprehensive isotopic study were conducted in typical regions (e.g., the Lhasa River basin). The followings are some main results: (1) The western Yarlung Zangbo River basin is affected by both westerlies and Indian summer monsoon, while the Indian monsoon dominates the middle and eastern parts. Monsoon air masses penetrated the Tibetan plateau through the eastern syntaxis of the Himalaya and the low passes of the middle Himalaya. These lead to decrease in river ?18O and d-excess and then increase from headwaters eastward. In the eastern drainage part, pronounced altitude effect of river ?18O is demonstrated (with a comprehensive lapse rate of 0.34‰/100m). In the middle drainage part, due to distinct seasonality in precipitation on two sides of the Himalaya range, river d-excess decrease dramatically with increasing distance north from the Himalaya (at lower altitude). The ?18O-?D relationship of river waters in this large basin also show distinct west-east variations due to the heavier aridity westward. The river water lines generally more and more deviate from the GMWL westward. (2) The river ?18O and d-excess in the Yarlung Zangbo River basin show pronounced seasonality. The river ?18O increase from spring to summer, show maximum nearly in June, and then decrease till the mimimum in August or September. This pattern is similar to that of the precipitation ?18O, indicating the dominance of the regional precipitation. Significantly low d-excess was shown for base flow in this basin, and the river d-excess generally show low values in spring and high values in summer. The occurring time of maxima depends on spring precipitation and meltwater conditions for a given region. The seasonality of river isotopes is the consequence of relavance of base flow, meltwater, sping and monsoonal precipitation. (3) In the Yarlung Zangbo River basin, the river water is generally isotopically more depleted when compared with local precipitation. The difference between river ?18O and local precipitation ?18O becomes larger and the correlation relationship between them becomes weaker from upstream downward. These are because the river water is mainly originated from the upper catchment above the sampling site. However, the Nianchu River water shows opposite conditions, which largely arises from strong influences of human activities within this basin. For data collected at various gauge locations in this large river basin, both the river ?18O and precipitation ?18O demonstrate strong linear relationship with geographical parameters (i.e. altitude and longitude). It is demonstrated that the lapse rates of river ?18O are much lower than precipitation ?18O. The linear relationship can be observed from July to September (typical monsoonal periods) for precipitation ?18O, while that can be observed from May to September, which may largely arise from the decrease |
| 中文关键词 | 稳定同位素 ; 印度季风 ; 西风 ; 高程效应 ; 水文循环 ; 雅鲁藏布江流域 |
| 英文关键词 | Stable isotopic composition Indian sunmer monsoon Westerlies Altitude effect Water cycle Yarlung Zangbo River basin |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院青藏高原研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287411 |
| 推荐引用方式 GB/T 7714 | 任伟. 雅鲁藏布江流域水体稳定同位素时空变化及其水文循环意义[D]. 中国科学院大学,2014. |
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