Although stable isotopes of hydrogen and oxygen in surface waters (especially in river waters) are useful tools to understand regional hydrological processes, relevant information at some upper reaches of large rivers in western China is still limited. During 2016–2017, we focused on the Liujiaxia Reservoir along the upper Yellow River, where we collected surface water samples at two locations, above and below the dam (identified as “lake water” and “river water”). The results show that the heavy isotopes in lake and river waters are enriched during the warm months, when the river discharge is large, and depleted during the cold months. The slopes of the water line (δ²H versus δ¹⁸O) for both the lake and river waters were lower than that of the global mean, due to evaporation. The different d values of the lake and river water reflect the regional evaporation and water sources.

The origin of bottled water can be identified via its stable isotope signature because of the spatial variation of the stable isotope composition of natural waters. In this paper, the spatial pattern of δ²H and δ¹⁸O values were analyzed for a total of 242 bottled water samples produced at 137 sites across China that were randomly purchased during 2014–2015. The isotopic ratios of bottled water vary between −166‰ and −19‰ for δ²H, and between −21.6‰ and −2.1‰ for δ¹⁸O. Based on multiple regression analyses using meteorological and geographical parameters, an isoscape of Chinese bottled water was created. The results showed that altitude among spatial parameters and precipitation amount and air temperature among meteorological parameters were major natural factors determining the isotopic variation of bottled water. Our findings indicate the potential and the significance of the use of stable isotopes for the source identification of bottled water. An analysis of different origin types (spring, glacier and unmarked) and several different brands of bottled water in the same location reflected different production processes and source signatures.

Based on 1260 tap water samples gathered monthly and 136 surface water samples collected seasonally in the eastern margin of the Qinghai–Tibet Plateau, the local tap water line, the basic spatiotemporal characteristics of tap water isotopes, and their indication for water source under different water supply modes were discussed, linking the local tap water supply and water source information. A new tap water isotopes data set based on dense sampling sites was established, which was reliable for the analysis of tap water isotope features, tap water supply management, and tap water sources. The main conclusions are: (1) The local tap water lines in Gannan and Longnan are δ²H = (7.06 ± 0.17) δ¹⁸O + (3.24 ± 1.75) (r² = 0.81, p < 0.01) and δ²H = (5.66 ± 0.09) δ¹⁸O + (−8.12 ± 0.82) (r² = 0.82, p < 0.01), respectively. (2) The annual mean δ²H and δ¹⁸O in tap water show an increasing trend from southwest to northeast. The seasonal differences of δ²H and δ¹⁸O in tap water in Gannan and Longnan are small. (3) The correlation of tap water isotopes with those in main source water is high, while that of isotopes in tap water with those in non-water source is low. Under the central water supply mode by local tap water company, tap water isotopes in Gannan where groundwater is the direct water source show weak connection with those in surface water and precipitation, and those in tap water in Longnan with surface water as main source water reveal good connection with isotopes in surface water. Under mixed water supply modes, tap water isotopes indicate that surface water is the main tap water source in Gannan and Longnan with multiple water sources.