Stable isotope variations of precipitation and streamflow reveal the young water fraction of a permafrost watershed
Stable isotope variations of precipitation and streamflow reveal the young water fraction of a permafrost watershed
复制标题
降水和水流的稳定同位素变化揭示了多年冻土流域的年轻水部分
DOI：
10.1002/hyp.11077
复制
发表时间：
2017
影响因子：
3.2
通讯作者：
Chen Xiaopeng
中科院分区：
文献类型：
--
作者：
Song Chunlin;Wang Genxu;Liu Guangsheng;Mao Tianxu;Sun Xiangyang;Chen Xiaopeng
径流年龄是控制径流产生、生物地球化学循环和污染物运移的集水区功能的基本描述。径流的年轻含水率(Fyw)可以用示踪剂数据准确地估计，它可以有效地表征不同类型流域的水龄比例。然而，永冻土集水区的Fyw值尚不清楚。我们选择了青藏高原多年冻土区的一个分水岭作为研究区域。研究了2009年解冻季节降水和径流的日间隔稳定同位素(氚和氧-18)。结果表明，降水和溪水的稳定同位素组成具有明显的时空变化。HYSPLIT反轨迹结果表明，研究区的水汽主要来自西风带和南方季风。多年冻土活跃层的融化过程显著改变了溪水的稳定同位素组成。土壤温度、土壤水分和气温是溪水中稳定同位素变化的主要驱动因素。我们估算了研究区五个集水区的年轻含水率，这是对青藏高原多年冻土集水区FYW的首次估计。结果表明，平均有15%的径流小于43天。进一步的分析表明，植被覆盖显著地控制了径流中年轻水的比例。这些结果将提高我们对多年冻土水文过程和水资源利用与保护的理解。
The streamflow age is an essential descriptor of catchment functioning that controls runoff generation, biogeochemical cycling, and contaminant transport. The young water fraction (Fyw) of streamflow, which can be accurately estimated with tracer data, is effective at characterizing the water age proportions of heterogeneous catchments. However, the Fyw values of permafrost catchments are not known. We selected a watershed in the permafrost region of the Qinghai‐Tibet Plateau (QTP) as our study area. Daily interval stable isotopes (deuterium and oxygen‐18) of precipitation and streamflow were studied during the 2009 thawing season. The results show that the stable isotope compositions of precipitation and stream water have significant spatial and temporal variations. HYSPLIT backwards trajectory results demonstrate that the moisture in the study area mainly derived from the westerlies and southern monsoons. Thawing processes in the active layer of the permafrost significantly altered the stable isotope compositions of the stream water. The soil temperature, soil moisture, and air temperature are the main drivers of the stable isotope variations in the stream water. We estimated the young water fractions of the five catchments in the study area, which were the first estimates of the Fyw in permafrost catchments in the QTP. The results show that an average of 15% of the streamflow is younger than 43 days. Additional analyses show that the vegetation cover significantly controls the young water fraction of the streamflow. These results will improve our understanding of permafrost hydrological processes and water resource utilization and protection.