Characteristic analysis of stable isotope variation in precipitation and rivers in Beilu River permafrost region

As an indispensable part of the Qinghai-Tibet Plateau (QTP) water cycle, precipitation and surface water in QTP plays an important role in exploring the permafrost hydrological process and in studying the history of permafrost development. Although enormous achievements in studying QTP precipitation and surface water have been made using isotopic methods, there has been a lack of relevant research on the subject in the Beilu River region of central QTP. In order to have a comprehensive understanding of the QTP water cycle and permafrost hydrological process, a study is conducted on the spatial-temporal characteristic of stable isotope variation in precipitation and rivers in the QTP Beilu River permafrost region. The isotopic composition and meteorological data from the region for the June-December period of 2011 are used to analyze the relationships among stable isotopes, daily average temperatures, precipitation amounts and flow water. Results show that temperature has a dominant effect on the stable isotopes in precipitation in the QTP Beilu River permafrost region. The isotopic seasonality of precipitation exists due to influences of both westerly and monsoon on local precipitation from June through December, which suggests that the stable isotopes in precipitation are controlled by both temperature and precipitation amounts. The stable isotope variation in rivers exhibits a similar behavior to that in precipitation, suggesting that rivers are recharged by the precipitation fallen in the QTP Beilu River permafrost region. The influence of precipitation on stable isotope variation in rivers is determined by precipitation amounts, i.e., the smaller the precipitation amounts are, the lighter the influences become. When compared to the local meteoric water line of the QTP Beilu River permafrost region, both slope and intercept of the δ¹⁸O-δD relationships are larger for rivers, suggesting that rivers are also recharged by other sources within the regional water cycle and influenced by evaporative fractionation.