Abstract A groundwater geochemistry study was carried out on 24 samples collected from different springs and wells situated in a plateau area at an elevation of 200–300 m in the Mehedinţi County, southwestern Romania. The study was motivated by the fact that springs have represented the only source of potable water in the region, only recently completed by tens of metres-deep well drillings. Spring distributions and geological data reveal the presence of a multilayered system situated in the Lower Quaternary deposits. The mean δ 18 O and δ D values of groundwater, −9.8 and −67.8‰, respectively, reflect the yearly weighted mean of the isotopic composition of precipitation, demonstrating locally derived recharge. The Piper ternary diagrams indicate that the dominant hydrochemical type is HCO 3 − –Ca 2+ –Mg 2+ with transition towards higher SO 4 2− and Mg 2+ contents to the deeper aquifer. The anions vary from HCO 3 − with transition to no dominant type and with Cl − contents higher for the shallower aquifer. The sequence of abundance of cations is generally Ca 2+ > Mg 2+ > K + > Na + and for anions: HCO 3 − > SO 4 2− > Cl − > NO 3 − > F − . Radiocarbon dating of dissolved inorganic carbon indicates a subrecent recharge of the aquifers. The vertical and lateral variations in groundwater chemistry may vary, and are influenced by lateral lithologic variation of the Quaternary clastic deposits. This is an unpredictable quality factor when taking the decision for the drinking water drill locations.

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 Randomness of fracture networks still makes channelized flow a challenge to track in hard-rock aquifers. While not underestimating geological and hydrological criteria that are also handled here through mapping exercises, this study raises an issue of water quality encountered in lifelong boreholes. Chemical classification checked against a recent conceptual model of bedrock aquifers gives birth to a new typology of groundwater in a complex granitic aquifer system located in the SW of Ivory Coast (West Africa). Major ion chemistry, borehole completion data, digital elevation model and satellite images are used to interpret the geochemical water facies as an expression of connexions between the saprolite and the saprock, or transient insulation. From major ions ratios, cumulate mineralization, carbonate equilibrium, stable isotopes, the maturation of ground waters and mixing between bedrock layers are described at seasonal and local scales. The results highlight some vertical feeding of the water table into the main saprock aquifer owing to shortcuts through the saprolite, along with the existence of dead-ends in the hydraulically active fracture network. Also, some influence of fault zones, either drain or barrier, is confirmed on the (Ca, Mg) bicarbonate water facies within the saprock.