Variations Of River Water Stable Isotopes On The Tibetan Plaeau And Adjacent Regions

It is important to use stable isotope techniques to study the water cycle, climate change process. Based on river water sampling on the Tibetan Plateau and adjacent regions, this Master’s thesis analyzes the spatial variations of δ18O of river water on the Tibetan Plateau and adjacent regions, presents the relationship between stable isotope and climatic conditions and elevation. The followings are some results of our study:(1) The thesis analyzed the spatial variation characteristics of the δ18O and deuterium excess in north-south river water in Tibetan Plateau. The results showed that because of the influence of different air masses, the δ18O of river water in Tibetan Plateau increased gradually from south to north. The study found that the δ18O of river water in different areas had different responses to altitude change, the elevation effect of the river water in Southern Tibet Himalayas was remarkable, but which in the north of Tanggula was not. There was also proved that the deuterium excess in river water in Tibetan Plateau had a significant spatial variation characteristic. Due to the different seasonal variation of precipitation in the north and south of the Tibetan Plateau, rain shadow effect, different sources of water vapor and vapor cycle mode in the north and south of the Himalayas, the deuterium excess in river water in the south of the Himalayas and the north of the Tanggula displayed two high-value areas, and which showed low-value areas in the north of the Himalayas and the south of the Tanggula.(2) The "temperature effect" lead to the river water samplings in Tibet plateau is higher in summer and lower in winter. The d values are higher in the winter and lower in the summer, due to the different moisture. The δ18O and deuterium excess in river water from West to East are increased at first and decreased subsequently. The lowest δ18O values of river water are in the Yarlung zangbo River. In winter, West glacial river water and groundwater recharge, and glacial melt less exposed to surface evaporative fractionation, makes the deuterium excess river water to a high value. There is a stable isotope kinetic fractionation during a snowfall in the eastern region, result in deuterium excess values increased.(3) The δ18O from east to West has a significant decreasing trend, which is due to most of the eastern Tibet plateau area are open lakes within river flood-affected, and most of the western region are closed lakes. Deuterium excess values are low in the west and high in the east region. In the summer, the air drier in the west region so that lake water evaporation is stronger that the d value in the west area is lower.(4) River water from upstream to downstream in Tarim, water evaporates are more strongly, so that the δ18O of river water in the downstream is higher. The Southwest of Tarim Basin river that Pamir nearby have an obvious elevation effect.