Plateau river research: spatial-temporal variations of δ18O and δd in the water of the Yarlung Tsangpo River and their controlling factors

Triple isotopes (δD, δ18O, δ17O) characteristic of river water and groundwater in an arid watershed from Qaidam Basin, Northwestern China: implications for hydrological cycle

Combining traditional stable isotopes (δD and δ18O) and triple oxygen isotope (δ17O) is conducive to tracing hydrological cycle processes. The application of triple oxygen isotopes primarily focuses on precipitation, which is lacking in river water and groundwater. In this study, the spatial variations of δD, δ18O, δ17O, d-excess and 17O-excess of river water and groundwater in the Golmud River basin as well as the correlation between them were investigated to elucidate water origin and assess the evaporation influence on water bodies during flood season. Spatial changes in δD, δ18O and δ17O of river water exhibit a decrease-increase-stability pattern contrary to that observed for d-excess, 17O-excess has no distinct trend but is higher at both the source and downstream regions. The results show that river water and groundwater originate from precipitation in the mountainous area, and the meltwater in the source region also contribute to the river water with high d-excess and 17O-excess during flood season. The combination of d-excess and 17O-excess reveal that river water is also affected by evaporation and mixing of river water in tributaries. It was found that the river water is recharged in the mountains, undergoes evaporation in the upstream region and leaks into groundwater in the midstream region, which is recharged by the groundwater and evaporated again in the downstream region. This study could provide a more comprehensive understanding of the potential and value of triple oxygen isotopes in the hydrological cycle.

Hydrogeochemical characteristics and recharge sources identification based on isotopic tracing of alpine rivers in the Tibetan Plateau

Alpine rivers originating from the Tibetan Plateau (TP) contain large amounts of water resources with high environmental sensitivity and eco-fragility. To clarify the variability and controlling factors of hydrochemistry on the headwater of the Yarlung Tsangpo River (YTR), the large river basin with the highest altitude in the world, water samples from the Chaiqu watershed were collected in 2018, and major ions, δ²H and δ¹⁸O of river water were analyzed. The values of δ²H (mean: -141.4‰) and δ¹⁸O (mean: -18.6‰) were lower than those in most Tibetan rivers, which followed the relationship: δ²H = 4.79*δ¹⁸O-52.2. Most river deuterium excess (d-excess) values were lower than 10‰ and positively correlated with altitude controlled by regional evaporation. The SO₄^2- in the upstream, the HCO₃^- in the downstream, and the Ca²⁺ and Mg²⁺ were the controlling ions (accounting for >50% of the total anions/cations) in the Chaiqu watershed. Stoichiometry and principal component analysis (PCA) results revealed that sulfuric acid stimulated the weathering of carbonates and silicates to produce riverine solutes. This study promotes understanding water source dynamics to inform water quality and environmental management in alpine regions.