基于稳定同位素示踪技术的青藏高原北麓河小流域冻土产流过程研究

Under a persistently warming climate and extensively degrading permafrost, the hydrological cycling and runoff generation processes in particular, in permafrost regions on the interior Qinghai-Tibet Plateau (QTP), are undergoing dramatic changes. They would have great influences on the spatiotemporal allocation of water resources at shallow aquifers in plateau permafrost regions. With the advantages of high precision and sensitivity, the hydrogen and oxygen stable isotopic technique is widely employed in studying the hydrological processes and water cycles in permafrost regions. It has provided an important method for studying the runoff generation in permafrost regions on the interior QTP, a region with paucity observational meteorological and hydrological data due to harsh climatic conditions. This program aims at studies on the seasonal variations in stable isotopes (δ18O, δD and d-excess) of different water components, (such as atmospheric precipitation, river and spring water, supra-permafrost water and ground ice) and their replenishment connections in the Beiluhe river watershed, a typical basin in continuous plateau permafrost region by using stable isotopic method and field observation data (meteorological data, permafrost and active-layer parameters, and hydrological data). In addition, this program will establish the relationships among air temperature, precipitation, and water level in active layer and runoff discharge, and then evaluate the contributions of supra-permafrost water (including the melting ground-ice) to the runoff generation under a warming climate. The study results of this program will innovate runoff generation research in permafrost regions on the interior QTP, and provide important original data and technical supports for studying the hydrological processes and water cycles on the QTP.

随着气候变暖，青藏高原多年冻土退化显著，很大程度上改变了冻土水文循环和产汇流过程，影响了青藏高原水资源的分配。氢氧稳定同位素技术具有精度高、敏感性强的优点，被广泛应用于冻土区水文过程和水循环研究中，这为研究资料相对贫乏、工作环境恶劣的青藏高原冻土区产流研究提供了科学方法。本研究拟采用稳定同位素技术，结合野外气象、冻土和水文观测数据，分析青藏高原北麓河多年冻土区典型小流域内不同水体（降水、河水、泉水、冻结层上水和地下冰）的稳定同位素季节变化特征以及水体之间的水力联系。通过分析流域内气象、冻土和水文参数之间的相关性，建立气温、降水、活动层水位与径流量之间的关系，进一步估算冻土退化背景下冻土层上水和地下冰融化对产流的贡献。以期能够在青藏高原冻土产流研究方面取得新的进展，为下一步深入研究青藏高原水文过程和水循环提供科学数据和技术支持。

青藏高原冻土退化改变了冻土区产流过程和水文循环。该项目基于稳定同位素技术，结合野外观测数据，系统研究了北麓河冻土小流域产流过程和水文循环。首先确定了青藏高原北麓河小流域降水水汽来源，结果显示，北麓河降水夏季受季风和再循环水汽的影响而冬季受西风控制；其次阐明了河水和热融湖塘的同位素水文季节变化规律，河水主要受降水（52.2%-53.5%）和地下冰融水（13.2%-16.7%）补给，而热融湖塘蒸发显著，同时受冻土和地下冰融水的影响；另外，利用钻探技术获得了北麓河不同植被和水文状况影响下的地下冰样品，基于同位素技术深入分析了地下冰的补给来源和成冰过程，结果显示上限附近地下冰主要受冻结层上水和降水的补给；最后，通过构建冻土水文概念模型结合同位素技术，明晰了不同水体之间的水力联系，发现上限附近的地下冰是冻土区重要的水文单元，对河水和热融湖塘水文过程有重要的影响。综上，项目研究成果为下一步青藏高原乃至第三极冰冻圈研究提供了重要的数据支撑和技术参考。在项目的资助下正式发表SCI 7篇，包括JCR一区5篇。依托本项目申请到后续科研项目6项。项目资助经费26万元，累计支出17.76万元，各项支出基本与预算相符。结余经费8.24万元，用于本项目后续研究和成果发表。