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The local meteoric water lines (LMWLs) reflect water sources and the degree of sub-cloud evaporation at a specific location. Lanzhou is a semi-arid city located at the margin of the Asian monsoon, and the isotope composition in precipitation around this region has aroused attention in hydrological and paleoclimate studies. Based on an observation network of stable isotopes in precipitation in Lanzhou, LMWLs at four stations (Anning, Yuzhong, Gaolan and Yongdeng) are calculated using the event-based/monthly data and six regression methods (i.e., ordinary least squares, reduced major axis, major axis regressions, and their counterparts weighted using precipitation amount). Compared with the global meteoric water line, the slope and intercept of LMWL in Lanzhou are smaller. The slopes and intercepts calculated using different methods are slightly different. Among these methods, precipitation-weighted least squares regression (PWLSR) usually had the minimum average value of root mean sum of squared error (rmSSEav), indicating that the result of the precipitation weighted method is relatively stable. Higher precipitation amount and lower air temperature result in larger slopes and intercepts on an annual scale, which is out of accordance with the summertime.

Salinity increase in groundwater was investigated in the area between Al-Zubair and Safwan, and close to the Khor Al-Zubair Channel of southern Iraq. Thirty-nine groundwater samples from the shallow aquifer and one sample from the Khor Al-Zubair Channel were analyzed. The mean total dissolved solids are 7556 mg/L. The δ2H and δ18O plot in two groups are below the global meteoric water line. Group A indicates the evaporation effect of irrigation return-flow, while group B is characterized by depleted δ18O values due to recharge under colder climate. Deuterium excess values plot within the region of modern precipitation and dilution of groundwater by precipitating water. The groundwater residence time is between 1000 and 2000 years and combining 14C -age with SO42− shows a contrasting effect on groundwater on both sides of Khedr Almai Fault and the Zubair anticline, which indicates the role of these geological structures on the hydrochemical evolution in the western part. Jabal Sanam shows no clear effect in this regard. The ratio Cl−/Br− and sulfate in groundwater showed that the measured salinity in groundwater is the result of a mixing process between groundwater, seawater intruding from Khor Al-Zubair Channel, and water from septic tanks in addition to dry and wet sea spray, and irrigation return-flow.

The variations of the stable isotope compositions in water provide critical information on hydroclimatic mechanisms. The climatological and hydrological processes in the Nujiang headwaters in the central Qinghai&ndash, Tibetan Plateau are extremely complex and are controlled by alternating continental/local recycled and maritime moisture. However, previous studies have only derived limited data from different types of water in the Nujiang headwaters. Therefore, aiming to understand the sources of stable oxygen (&delta, 18O) and hydrogen (&delta, 2H) isotopes&rsquo, compositional variability and how these are related to hydroclimatic processes, we measured &delta, 18O and &delta, 2H values from surface waters, snow and precipitation across the Nujiang headwaters from April to September 2018. We found higher &delta, 18O (&minus, 13.7&permil, ), &delta, 2H (&minus, 101.8&permil, ) and deuterium excess (d-excess, 7.6&permil, ) values in the non-monsoon season and lower values in the summer monsoon season. Our findings indicated that the &delta, 2H compositions were significantly affected by different moisture sources in this region. The slope (6.66) and intercept (&minus, 14.90) of the surface water line (SWL: &delta, 2H = 6.66 &delta, 18O &minus, 14.90, R2 = 0.98) were lower than those of the local meteoric water line (LMWL: &delta, 2H = 9.50 &delta, 18O + 41.80, R2 = 0.99) and global meteoric water line (GMWL), indicating that precipitation was the primary water vapor source for surface water, and evaporation was the dominant hydrological process for the Nujiang headwaters. In general, &delta, 2H tended to be negatively correlated with precipitation and air temperature. In addition, &delta, 2H values in the Nagqu River were inversely correlated with the intensity of discharge, highlighting a precipitation-driven isotope-discharge pattern. Our findings provide a theoretical basis for the hydroclimatic mechanisms occurring in the Nujiang headwaters and further augment our understanding of the southern&ndash, middle&ndash, northern hydroclimate in the Qinghai&ndash, Tibetan Plateau.

Stable isotopes of oxygen and hydrogen were used to estimate seasonal contributions of precipitation to natural spring recharge in Beijing&rsquo, s mountainous area. Isotopic compositions were shown to be more positive in the dry season and more negative in the wet season, due to the seasonal patterns in the amount of precipitation. The local meteoric water line (LMWL) was &delta, 2H = 7.0 &delta, 18O &minus, 2.3 for the dry season and &delta, 2H = 5.9 &delta, 10.4 for the wet season. LMWL in the two seasons had a lower slope and intercept than the Global Meteoric Water Line (p &lt, 0.01). The slope and intercept of the LMWL in the wet season were lower than that in the dry season because of the effect of precipitation amount during the wet season (p &lt, 0.01). The mean precipitation effects of &minus, 15&permil, and &minus, 2&permil, per 100 mm change in the amount of precipitation for &delta, 2H and &delta, 18O, respectively, were obtained from the monthly total precipitation and its average isotopic value. The isotopic composition of precipitation decreased when precipitation duration increased. Little changes in the isotopic composition of the natural spring were found. By employing isotope conservation of mass, it could be derived that, on average, approximately 7.2% of the natural spring came from the dry season precipitation and the rest of 92.8% came from the wet season precipitation.

Coal mining, as one of the key drivers of land degradation worldwide, caused land subsidence problems. In this study, we conducted experimental research to explore the reclaimed mine soil (RMS) water dynamics and its sources in relation to reclaimed land use types using stable water isotopes in the Longdong coal mining area with high groundwater level in east China. We collected water samples seven times in 2017 from all of these water bodies (precipitation, surface waters (river water and water from subsidence pits (WSP)), groundwater and soil water). Our main findings are three fold: (1) the values of slope and intercept of the local meteoric water line of Craig (LMWL) of precipitation for the study area are higher than the global meteoric water line of Craig (GMWL) because of the humid monsoon climate zoon, and the values of &delta, D and &delta, 18O of surface waters and soil water and groundwater deviated from LMWL to some extent with a range of 5%&ndash, 30%, and the D and 18O of precipitation and the surface waters have higher seasonal variation than groundwater, (2) the values of &delta, 18O of RMS for the whole soil profile (0&ndash, 100 cm) are lower than that of precipitation and have obvious seasonal variations and great fluctuation in the topsoil (0&ndash, 30/40 cm) and decrease at depth (30/40&ndash, 70 cm) and stable in deep soil layers (below 70 cm deep), (3) the RMS with forest and crop enhanced water infiltration capacity and soil water mixing strength compared with the waste RMS, so establishment of forest and crops should be encouraged in the RMS, (4) the main sources of topsoil (0&ndash, 30 cm for crop and 0&ndash, 40 cm for forest) of RMS are precipitation through infiltration, the main supply for deep soil water (below 70 cm deep) is groundwater, and the soil water for the middle deep soil layers (30/40&ndash, 70 cm) is mainly from mixing sources of precipitation, groundwater, and river water through pant root water absorbing and groundwater upshifting.