Abstract δ 2 H and δ 18 O values of precipitations follow an empirical linear relationship at the global scale that is called the Global Meteoric Water Line (GMWL) and characterized by a slope of 8. However, Local Meteoric Water Lines (LMWLs) may have different slopes S depending on their geographic situation. Monthly δ 2 H and δ 18 O of precipitation have been compiled from European International Atomic Energy Agency (IAEA) stations. Those data allowed the calculation of the slopes S of the δ 2 H– δ 18 O LMWL determined for each station. S increases with longitude ϕ from c. 5 (Portugal) to c. 9 (Russia) – they are positively correlated with relative humidity (RH), negatively with temperature and positively with the mean intra-annual amplitude of temperatures, which is a proxy of continentality. Slopes of 5–6, recorded in SW Europe, reflect mean RH (70–75%) and sea surface temperatures ( c. 25°C) of the Central Atlantic Ocean where the main flux of moisture is formed before being transported by the westerlies. In addition, falling water droplets within an air column with a high RH (>80%) and low temperature are expected to escape sub-cloud evaporation. Therefore, slopes with values close to 9 are considered to reflect isotopic equilibrium conditions during the condensation of water vapour in clouds.

Abstract In this chapter, we analyse the influence of the Carpathian Mountains on the variability of stable isotopes in precipitation by employing a combination of observed and model data. Overall, the mean value of the stable isotopes in precipitation over the Carpathian Mountains, based on observational data, was −9.8‰ for δ 18 O and −68.6‰ for δ 2 H. The local meteoric line, using all samples from the study sites, was δ 2 H = 7.65 × δ 18 O + 5.82. The simulated δ 18 O, based on the ECHAM5-wiso isotopes enable model, showed good agreement with the observed isotopic data. By comparing all the monthly values of the observed isotopic data from all analysed stations and the corresponding model data, a correlation coefficient of 0.76 ( n = 455, p < 0.001) was obtained. The spatial distribution of the simulated δ 18 O values in precipitation had the lowest values over the Romanian Carpathian Mountains and the highest values over the extra-Carpathian area, with the maximum in southeastern Romania. This pattern was strongly influenced by the Carpathian Mountains orography. Using the simulated δ 18 O data, we show that the spatial distribution of the δ 18 O values increases with temperature and decreases with altitude and latitude (−0.5‰ for δ 18 O per degree of latitude). The continental gradient is characterized by a polynomial trend of the second degree in the form of a large-open ‘U’ shape, and the general pattern of the δ 18 O values follows the spatial distribution of the Carpathian Mountains.

Abstract To investigate the influence of local climate and transboundary circulation of moisture on the stable isotope of precipitation in Ramnicu Valcea, Romania, monthly values of δ 2 H, δ 18 O, deuterium excess (d excess ), temperature, relative humidity and precipitation were determined between January 2012 and December 2018. Monthly analysis showed differences in d excess varying between 24.2‰ (October 2015) and −23.7‰ (July 2013) with a multi-annual average of 6.1 ± 5.9‰, suggesting an Atlantic origin of moisture with episodic Mediterranean transport. Also a significant correlation between the North Atlantic Oscillation on the local temperature during winter season was noticed. The local meteoric water line (LMWL) for the entire period showed slope and intercept values similar to those for neighbouring localities with the same altitude. When the analysis was extended to summer (April–October) and winter (November–March) seasons, the LMWL slope and intercept were different, reflecting the summer–winter difference in temperatures and air circulation. The monthly values of all parameters formed equal-spaced time series whose detailed analysis confirmed at p < 0.01 that δ 2 H, δ 18 O, temperature and relative humidity show a well-evidenced one-year periodicity. In contrast, precipitation and d excess seasonality were almost unrecognizable, most probably owing to the reduced number of observations.

Abstract Water, the vital element of the environment, considered for long time an inexhaustible and renewable resource, can have a limiting or favourable potential in the socioeconomic development of a region. Given that Romania's NE (Eastern Carpathians and the northwestern part of the Moldova Plateau) is undergoing increased competition for water resources, triggered by the intensification of agriculture and industrial development, better knowledge of the hydrological processes and the quality of surface water is required. The main purpose of the present study was to identify the hydrological processes determining the quality of surface waters based on analyses of the stable isotopic composition of water from precipitation, rivers and lakes and its quality parameters. For this, water samples were collected from 29 river sections, two lakes and a precipitation monitoring point over a period of 12 months (January to December 2019). The results show that the changes in the isotopic composition of precipitation and surface water are mainly controlled by air temperature, which, in turn, is influenced by the large-scale atmospheric circulation and other factors (e.g. precipitation amount, season, altitude). At the same time, the chemical analyses indicate that the water resources of the study area are predominantly characterized by a good chemical and ecological state, except for two sampling points with a moderate state and three with a poor ecological state.

Abstract Year-long continuous radon monitoring was carried out (using Sarad Radon Scout devices) in a dwelling with high radon levels in the karst region of Slovenia. Two living rooms were selected: one on the ground floor with normal housework activities; and the second, on the first floor, closed and unattended. Meteorological data were also recorded. The following seasonal geometric means of radon activity concentration (kBq m −3 ) have been found: 6.28 ×/: 3.05 for spring, 1.25 ×/: 3.78 for summer, 5.17 ×/: 2.03 kBq m −3 for autumn and 9.83 ×/: 1.48 for winter on the ground floor; and 1.43 ×/: 3.71 for spring, 0.168 ×/: 2.49 for summer, 1.08 ×/: 2.39 for autumn and 2.08 ×/: 2.14 for winter on the first floor. Results are supported by additional radon measurements in other rooms; and in water the results indicate a strong radon source associated with an underground karst shaft.

Abstract The sensitivity of glacier mass balance (MB) in response to climatic perturbations has made it an important parameter of study from hydrological, climatological and glaciological point of view. To monitor the health of any glacier system, long-term MB observations are required. These observations among Himalayan glaciers are not available consistently and large glaciers are not often monitored for mass balance due to logistical challenges. One such glacier is the Gangotri, situated in the western Himalaya. In the present study an attempt is made to model the MB over the Gangotri glacier, the biggest glacier in the Ganga basin and also the point of origin of the River Ganges. The mass balance of the Gangotri glacier is estimated during the time period 1985–2014 using two different methods: ice-flow velocity; and energy balance modelling using regional model (REMO) outputs and in situ automatic weather station (AWS) data. The geodetic method is used for the nearby Dokriani glacier, where field-based MB measurements are available. MB of Gangotri glacier estimated for 2001–14 using the ice-flow velocity method is −0.92 ± 0.36 m w.e. a −1 ; for 2006–07, MB using AWS and Tropical Rainfall Monitoring Mission (TRMM) data with the energy balance modelling approach is −0.82 m w.e. a −1 ; and for 1985–2005, MB using REMO data with the energy balance modelling approach is −0.98 ± 0.23 m w.e. a −1 . Using the surface velocity method, it is estimated that the glacier lost 9% of its volume during the period 2001–14. The glacier vacated an area of 0.152 km 2 from the snout region, and retreated by 200 m in the last 14 years. MB values estimated for the Gangotri glacier from different methodologies are remarkably close, suggesting them to be suitable methods of MB estimation. TRMM, High Asia Refined (HAR-10) and Asian Precipitation Highly Resolved Observational Data Integration Towards Evaluation of water resources (APHRODITE) data are used to estimate the precipitation over the glacier. The study suggests that the glacier-wide estimation of weather parameters needs to be improved for more accurate estimation of glacier mass balance. Supplementary material: The snow-covered area, for months Jan-Dec, obtained for Gangotri glacier using Landsat data and NDSI (normalized differencing snow index) for year 2014 is available at https://doi.org/10.6084/m9.figshare.c.3888091

Abstract Melting of snow and ice contributes a large amount of water to the streamflow in the Satluj River. During the winter season, there is low base flow in the river as compared to spring and summer. Temperature is one of the key factors which directly impacts snow and ice melting throughout the year. A substantial amount of snowmelt only occurs when all the snow in a pack reaches isothermal condition. It is therefore very important to know the duration of impact of temperature on snowmelt runoff. Since the Himalayas have very few stations observing hydrological as well as meteorological conditions, it is difficult to validate the snowmelt models and examine changes in small-scale features in river basins of the region. The present study examines the annual cycle and interannual variability of runoff in the Satluj Basin in the western Himalayas and documents the impact of temperature on snowmelt runoff of Satluj River using daily in situ data for the period 1982–2005. A multivariate regression model using precipitation and surface temperature has been developed to predict the discharge of Satluj River at a daily scale. It is seen that after every warm phase and cold phase of temperature, the impact persists for around one month and affects the snowmelt runoff during January, February and March at lower- and higher-elevation stations such as Bhakra and Kasol, respectively. The effect of a large fall and rise in temperature is noticed on snowmelt runoff measured at all the discharge stations, while a small temperature change does not affect the observed discharge at all the stations. The remote sensing and reanalysis data are consistent with in situ data in the basin, and there is no major change in peak month of discharge or the amplitude during two different periods at Rampur gauge station.