Base flow in the Yarlungzangbo River, Tibet, maintained by the isotopically-depleted precipitation and groundwater discharge
Base flow in the Yarlungzangbo River, Tibet, maintained by the isotopically-depleted precipitation and groundwater discharge
复制标题
西藏雅鲁藏布江的基流由贫同位素降水和地下水排放维持
DOI：
10.1016/j.scitotenv.2020.143510
复制
发表时间：
2021
影响因子：
9.8
通讯作者：
Jiarong Wang
中科院分区：
文献类型：
--
作者：
Hongbing Tan;Xi Chen;Dongping Shi;Wenbo Rao;Jing Liu;Jintao Liu;Christopher J. Eastoe;Jiarong Wang
青藏高原伸展裂谷系统可能向河流输送大量地下水，但这些地下水的来源和流动路径尚不清楚。雅鲁藏布江是唯一一条从西向东横穿青藏高原南部的大河，它遵循着一条被伸展正断层切割的主要缝合带。断层会影响地下水向河流排放的流动路径。在这项研究中，分析了沿YR的氧、氢同位素、主要离子和222Rn浓度，并解释了与构造地质和构造的关系。YR显示出同位素和化学成分的突变，并伴随着中段与NE-SW向裂谷相交的流量的大幅增加。δD和δ18O的低值以及中游主要离子和222Rn的高浓度表明，水的同位素和化学变化受到各种可能的水来源的影响，例如高海拔冰川融化的补给和地下水的排放。地下水贡献了中游河流流量的27%至40%。来自高海拔冰川融化的同位素光融水不能解释目前地下水外流的同位素组成。地下水的氧、氢同位素数据可以很好地解释为较冷时期(如晚更新世至全新世早期)的古降水。中游地区古地下水流量约为36亿×108m~3水量平衡不平衡。该研究首次为大型活动张性断裂带中大江大河的地下水排泄来源提供了明确的同位素证据，并证实了青藏高原地下水流动的区域规模。了解青藏高原径流和地表水循环的特征和变化，有助于在变化的环境下进行水资源管理。
The extension-induced rift systems on the Tibetan Plateau (TP) may convey large amount of groundwater to rivers, but sources and flow paths of such groundwater are unknown. The Yarlungzangbo River (YR) is the only large river that traverses the southern Tibetan plateau from west to east, following one major suture zone that is cut by extensional normal faults. The faults could influence the flow paths of groundwater discharging to the river. In this study, O and H isotopes, major ions and222Rn concentrations are analyzed along the YR, and interpreted in relation to structural geology and tectonics. The YR exhibits an abrupt change of isotopic and chemical compositions along with a large increase in flow where the middle reach intersects NE-SW-trending rifts. Low values of δD and δ18O and high concentrations of major ions and222Rn in the middle reach show that waters are modified isotopically and chemically by a variety of possible water origins, such as recharge of high-altitude glacier melt and discharge from groundwater. Groundwater contributes 27 to 40% of the river flow in the middle reach. Isotopically-light meltwater from high-altitude glacier melt cannot account for the isotope composition of the present outflow of groundwater. The O and H isotope data in the YR and discharging groundwater can be well explained by the groundwater originated as paleo-precipitation during a cooler time, such as the late Pleistocene to early Holocene. The paleo-groundwater discharge can account for about 36 × 108m3water budget unbalance in the middle reach. The study provides the first clear isotope evidence for the source of groundwater discharge into a large river through favorable conduits in large-scale active tensile fault zones and confirms the regional scale of groundwater flow on the Tibetan Plateau. Understanding the characteristics and changes of streamflow and surface-groundwater circulation on the Tibetan Plateau will help to manage water resources under a changing environment.