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We use 84 rainfall samples collected during June to September 2017 from the Dongkemadi basin, source region of the Yangtze River, China, to analyze the characteristics and influencing factors of stable isotopes in groundwater, and further discuss the groundwater recharge sources. The results showed that the range of groundwater δ 18 O values in this permafrost region varied from -15.3‰ to -12.5‰ (mean -14.0‰). The range of δ D values in groundwater varied from -108.9‰ to -91.7‰ (mean -100.2‰). Compared with local atmospheric precipitation, groundwater isotopes were relatively enriched. The slope and intercept of the groundwater line (GL) in the study area were both lower than of those of the global and local meteoric water lines (GMWL and LMWL), thus indicating that groundwater in the study area was subjected to evaporation during rainfall recharge of groundwater. The d -excess values of groundwater varied from 4.9‰ to 25.0‰ (mean 11.6‰), which was close to the average d -excess value determined for global average rainfall (10‰), but lower than that of rainfall in the study area (15.1‰). The influencing factors on the composition and variation of groundwater isotopes were different in different periods. The permafrost active layer was relatively thin during periods of increasing air temperature, and groundwater isotopes were significantly affected by air temperature. A temperature decrease during the latter part of the sampling period, when the thickness of the permafrost active layer was still increasing, further increased the retention time of infiltrating rainfall in the soil, thereby eventually leading to evaporation that strengthened the enrichment of heavy isotopes in the groundwater. According to the topographic characteristics of the Dongkemadi basin, the isotopic characteristics of the groundwater, and the factors influencing the isotopic composition, we conclude that rainfall was the main source of groundwater recharge. The results of this study provide a scientific basis for studying water cycle processes in the permafrost regions of the source region of the Yangtze River.

Using 64 precipitation samples collected from June to September 2013 in the Dongkemadi Basin in the source region of the Yangtze River, the pH, conductivity, and main ionic concentration characteristics of precipitation were analyzed. The main ionic sources of precipitation and their relationships with atmospheric circulation were examined using factor analysis, correlation analysis, enrichment factor analysis, and backward trajectory analysis. The results showed that the range of precipitation pH values varied from 5.26 to 9.25 with a weighted average of 6.70, and conductivity ranged from 0.23 to 28.70 μS·cm -1 with a weighted average of 3.45 μS·cm -1 . The conductivity of precipitation was lower than for the Mt. Waliguan basin (China Global Atmosphere Watch baseline observatory). The total ionic concentrations in the precipitation ranged from 7.0 to 376.9 μeq·L -1 with a weighted average of 40.8 μeq·L -1 . The ranked order of ionic concentrations was HCO 3 - > NH 4 + > Ca 2+ > NO 3 - > SO 4 2- > Na + > Cl - > K + > Mg 2+ . HCO 3 - , NH 4 + ,Ca 2+ , and NO 3 - were the dominant ions, which accounted for 74.75% of the total ionic concentration. Fractional acidity (FA) analysis showed that 97.8% of the precipitation acidity was neutralized by alkaline constituents. Neutral factor (NF) analysis indicated that NH 4 + and Ca 2+ were the dominant neutralization constituents in the precipitation. The precipitation ions in this study area were mainly derived from terrestrial material, while input from marine sources was relatively low. Backward trajectory analysis revealed that the total ionic concentrations varied significantly between the different sources, which followed the order of local sources>westerly sources>monsoon sources. This indicates that different atmospheric circulation conditions and air mass sources have a significant influence on the chemical composition of precipitation in this area. To some extent, the chemical characteristics of precipitation could reflect the air quality and background values for remote areas due to the limited effect of human activities. The results of this study provide a scientific basis for the protection of water quality and the assessment of the impact of human activities on the atmospheric environment in the source region of the Yangtze River.

Based on the stable isotopes of 73 precipitation samples continuously collected from May to October 2014 and related meteorological statistics in the Dongkemaldi Basin, the characteristics of δ D, δ 18 O, and d -excess of precipitation, as well as the correlations between δ 18 O and the rainfall amount and air temperature were analyzed. The moisture sources were tracked by the HYSPLIT model to further estimate the contribution of different water vapor sources to the rainfall amount. The results showed that the range of δ 18 O and δ D values varied from -26.5‰ to 1.9‰ and -195.2‰ to 34.0‰, respectively; meanwhile, the δ 18 O and δ D values in precipitation fluctuated greatly with time in response to water vapor transport from different moisture sources of the Qinghai-Tibet Plateau. The slope and intercept of the Local Meteoric Water Line (LMWL) were both higher than those of the Global Meteoric Water Line (GMWL) and close to the LMWL in the northern area of the Qinghai-Tibet Plateau. The relationship between δ 18 O and δ D in different precipitation types showed significant differences, which were mainly related to the source of water vapor and meteorological conditions during the process of precipitation formation. Because of the influence of local evaporation and the transport process of water vapor, the d -excess values of atmospheric precipitation were relatively large; the δ 18 O in precipitation had a significant amount effect, but had no temperature effect, thus indicating that the rainfall amount was more effective in controlling the stable isotope content of atmospheric precipitation than temperature. The modeled trajectory of vapor sources showed that water vapor of precipitation was mainly derived from the marine vapor carried by the southwest monsoon, local moisture, and the westerly water vapor, and their contributions to the rainfall amount were 43%, 36%, and 21%, respectively. The results of this study can contribute to further understanding of the atmospheric circulation characteristics and water cycle process of the Dongkemadi basin in the headwaters of the Yangtze River.

To analyze the hydrochemical characteristics of river water and snow meltwater during snow-melting period in the Kayiertesi River, the headwaters of the Ertis River, samples of river water and meltwater were collected every day during March and April, 2014. Furthermore, the combination of descriptive statistics, Gibbs Figure and Piper Triangular diagrams of anions and cations were used for hydrochemical analyses. The results showed that the major ion compositions and hydrochemical types were significantly different between river water and snow meltwater. The total dissolved solid (TDS) in the river water ranged from 24.9 to 50.3 mg · L⁻¹. The major cations of river water were Ca²⁺ and Na⁺, accounting for 61% and 17% of the total cation equivalent concentration, respectively. Meanwhile, HCO₃⁻ constituted about 95% of the total anions concentration. The hydrochemical type of river water was HCO₃⁻-Ca²⁺. The chemical composition of river water samples located in the middle with a deviation to left of Gibbs model, indicating that the major chemical process of river water was controlled by rock weath ring and precipitation but rock weathering played a more important role.

Stable isotope techniques provide a new approach to study soil water movement. The precipitation and the soil water from 0 to 100 cm soil layer in 4 kinds of typical vegetation types (forest, shrub forest, grassland and non-forest land) over the water source area of Yuanyang terrace were sampled, and their isotope compositions were analyzed, aimed to understand the characteristics of stable isotopes in different depth of the soil water. The results showed that the meteoric water line in the water source area of Yuanyang terrace was δD = 6.838 4δ(18)O-5.6921 (R2 = 0.8787, n = 20), the slope and intercept were less than the global atmospheric precipitation. The hydrogen and oxygen stable isotopes in the soil water of the 4 kinds of typical types was lower than the local meteoric water line side and the fluctuation of isotope value on surface soil profile was greater. With the increasing soil depth, the fluctuation of delta 18O value was smaller and smaller, especially in the 80-100 cm soil layer which was the most obvious. The delta 18O values of the deep soil water in forest and grassland were higher than that in the surface soil. while it was on the contrary in shrub forest and non-forest land.

To analyze the major ion chemistry of water in the upper reach of the Shule River Basin and possible controls, samples of river water, groundwater, precipitation, melt water were collected and methods including descriptive statistics, Gibbs Figure, Piper Triangular diagrams of anions and cations were comprehensive used. Results showed that the major ion compositions and hydrochemical types were significantly different in different waters such as stream water, groundwater and precipitation. The total dissolved solid (TDS) in the river water ranges between 51.7 to 432. 3 mgL-1 with an average of 177.7 mgL-1. The major cations of river water are Ca2+ and Mg2+, accounting for 45% and 31% of the cations respectively. Meanwhile, HCO(3)- constituted about 75% of the anions. The hydrochemical type of river water is HCO(-)(3)-Ca2+-Mg2+. Owing to the interaction between the river and layer, the concentration of SO(2-)4 is relatively higher. Comparing major ion concentrations of the river water with local groundwater and precipitation, concentrations of the river water ranged between precipitation and groundwater but were much closer to the concentration of groundwater, indicating that the surface water was recharged by a mixture of precipitation and groundwater while groundwater is dominant. The chemical composition of surface water samples located in the middle and a bit upper of Gibbs model, which indicates that the major chemical process of river water is controlled by rock weathering and evaporation-crystallization but rock weathering plays a much more important role.

Under the increasing pressure of water shortage and steppe degradation, information on the hydrological cycle in the steppe region in Inner Mongolia is urgently needed. Major ions are widely used to identify the hydrological processes in a river basin. Based on the analysis results of 239 river water samples collected in 13 sections along the Xilin River system during 2006 to 2008, combined with data from groundwater and precipitation samples collected in the same period and the meteorological and hydrological data in the Xilin River Basin, hydrochemical characteristics and the chemistry of major ions of the Xilin River water have been studied by means of Piper triangle plots and Gibbs diagrams. The results showed that: (1) the total dissolved solid (TDS) in river water mainly ranged between 136.7 mg x L(-1) and 376.5 mg x L(-1), and (2) it had an increasing trend along the river flow path. (3) The major cations and anions of river water were Ca2+ and HCO3-, respectively, and the chemical type of the river water varied from HCO3- -Ca2+ in the headwater area to HCO(3-)-Ca2+ Mg2+ in the lower part. (4) The variation in the concentration of major irons in surface water was not significant at the temporal scale. Usually, the concentration values of major irons were much higher in May than those in other months during the runoff season, while the values were a bit lower in 2007 than those in 2006 and 2008. Except for SO4(2-), the concentrations of other ions such as Ca2+, Na+, Mg2+, K+, Cl- and HCO3- showed a upward trend along the river flow path. Comparing major ion concentrations of the river water with those of local groundwater and precipitation, the concentration in river water was between those of precipitation and groundwater but was much closer to the concentration of groundwater. This indicated that the surface water was recharged by a mixture of precipitation and groundwater, and groundwater showed a larger impact. The Gibbs plot revealed that the chemical compositions of the river water were mainly affected by rock weathering in the drainage area.

In order to better understand the hydrological process in Xilin River Basin, 248 water samples were collected in 13 sections (10 were at the mainstream and 3 were at the three tributaries) over the Xilin River during 2006-2008 and thereafter analyzed by high resolution inductively coupled plasma mass spectrometry (ICP-MS) for 20 trace elements. The temporal and spatial distribution characteristics of trace elements were obtained. The results showed that the average concentration values of trace elements were 0. 1-10 microg x L(-1). Most of those values were at the concentration ranges of precipitation and groundwater and very close to the values of groundwater, indicating that the surface water was recharged by precipitation and groundwater especially by groundwater. The variation of concentration of trace elements in surface water was not strong at the temporal scale. Usually, the concentration values of trace elements were higher in April and May than those in July and August while those values were a bit lower in 2007 than in 2006 and 2008. Most of the trace element concentrations showed a upward trend from upstream to downstream. The enrichment of trace elements was contributed to the recharge of tributaries and groundwater, the evaporation of the stream water.

To study the variations of deltaD and delta18O in precipitation, 301 samples were sampled during 2002-2004 in 6 sites in the Heihe River basin, Northwestern China. The deltaD and delta18O values ranged from 59 per thousand to -254 per thousand and 6.5 per thousand to -33.4 per thousand, respectively. This wide range indicated that stable isotopes in precipitation were controlled by different condensation mechanisms as a function of air temperature and varying sources of moisture. delta18O in precipitation had a close positive relationship with the air temperature, i. e., a clear temperature effect existed in this area. At a monthly scale, no precipitation effect existed. On the other hand, a weak precipitation effect still accrued at precipitation events scale. The spatial variation of delta18O showed that the weighted average delta18O values decreased with the increasing altitude of sampling sites at a gradient of -0. 47 per thousand/100m. A regional Meteoric Water Line, deltaD = 7.82 delta18O + 7.63, was nearly identical to the Meteoric Water Line in the Northern China. The results of backward trajectory of each precipitation day at Xishui showed that the moisture of the precipitation in cold season (October to March) mainly originated from the west while the moisture source was more complicated in warm season (April to September). The simulation of seasonal delta18O variation showed that the stable isotope composition of precipitation tended to a clear sine-wave seasonal variation.

Investigation of meltwater chemistry may provide information to understand the significance of glacier in estimating of water provenance. Most notably, the role of electrical conductivity (EC) variation in meltwater during glacier melting season has attracted considerable attention, since this may reflect the water flux. Analyses for pH and EC in 229 bulk meltwater samples have provided information about water provenance at Dongkemadi Glacier basin, an outlet tongue from the Tanggula Pass, Tibetan Plateau. The samples were collected at 14:00 from 12th May to 27th September in 2005 at site of controlled meltwater flux. The results document the following findings. First phase of runoff was mainly supplied by snow and glacier ice meltwater, 31% and 65%, respectively, and the snow including fresh snow and winter deposited snow. Secondary phase of flux primarily was supplied by glacier ice meltwater and precipitation, but meltwater of frozen water in soil also has some contribute to flux, but only 2%. Third phase, ice bulk meltwater decreased and fresh snow meltwater increased. In different precipitation modalities variation trends of pH value and EC are following an orderd snow > rainwater > hailstone.