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Water resources management is particularly challenging in water-scarce basins, where low water availability is combined with a potential water demand exceeding the supply capacity of the natural system. This is the case of the Segura River Basin in south-eastern Spain. This paper aims at analysing the usefulness of incorporating new hydrological data and perspectives to improve the understanding of water availability and management and help promote more integrated water planning in the Segura Basin. In this basin, agriculture amounts to approximately 1366 hm3/year and accounts for 80% of the total blue water use. The forest and agriculture use of soil water amounts to 3065 and 1962 hm3/year, respectively. The unaccounted virtual water trade is also relevant and helps in mitigating water scarcity in the basin. The basin is a net virtual water-exporting region, with an average export of 1598 hm3/year, mainly in the form of fruits and vegetables, and imports approximately 1253 hm3/year, mainly related to feed for pig farms. Virtual water imports are four times larger than the disputed water transfer rate to the Segura Basin from other river basins. Water productivity analyses by sub-sectors are useful in understanding the economic rationale of the basin activities. Two types of agriculture coexist in the basin, namely, intensive industrial agriculture and occupational farming, which maintain the territory and landscape. From a Mediterranean country perspective, the analysis recommends considering climate fluctuations and temporal variability and trends of water availability and use, moving beyond the average values considered in river basin management plans. Groundwater reserve depletion continues to occur at a rate of 231 hm3/year, as water from wells is currently cheaper than using desalinated water in farms, and it does not cause boron-related water quality problems for irrigation. If socially costly administrative measures are not taken, groundwater reserve depletion will continue. The project 'Análisis académico del Plan Hidrológico de la demarcación hidrográfica del Segura 2015-2021 a la luz de modernos conceptos de la ciencia de los recursos del agua' (Academic analysis of the Segura Water District Water Plan from the point of view of water resources modern concepts) provided the ideas and data for this work. This project has been carried out by the Royal Academy of Exact, Physical and Natural Sciences of Spain with the support of the Segura Water Authority , the Botin Foundation , Obra Social La Caixa and Caja Navarra Foundation . Many experts have contributed to its development, and all of them are credited in Aldaya et al. (2017) .

In the arid area of northern Chile, groundwater resources in the Andean formations are essential for native populations, ecological services, mining, and other human activities. Validated conceptual hydrogeological models are required for current and future water and land management. This work aims to explain the processes controlling the origin and distribution of recharge and groundwater composition in the Andean Precordillera and Altiplano of the Tarapaca Region of northern Chile, using major solutes in spring, river, and well water, and the stable and radioactive isotopes of water oxygen, hydrogen, and dissolved inorganic carbon. The waters are mainly of the Na-Ca-SO4 type. Processes controlling the chemical evolution of waters are atmospheric dust contribution, evapo-concentration, and enhanced volcanic rock weathering, as well as halite dissolution in some locations. The isotopic composition of Precordillera eastern flank water samples follows an evaporation line, while those in the western flank, in the Altiplano, follow a line that is parallel to the local meteoric line, suggesting unsaturated zone evaporation processes of infiltrated rainfall. δ13CDIC contents (-2 to -27‰) indicate mixing processes, volcanic CO2 in the Altiplano, and calcite dissolution in some sectors. In the western depression, the only recharge is due to water infiltration in creek channels. In the highland areas, 5–25% of precipitation produces recharge. The estimated groundwater renewal time in the Precordillera was 3–14 kyr. The piezometric elevation in the Precordillera due to low-permeability intrusive rocks and local recharge prevents the east-west groundwater transfer from the Altiplano to the western depression and explains why the volcanic CO2 in the Altiplano basins is not observed on the western flank. These results provide new insights for the evolution of water quality in volcanic aquifers in arid environments and provide considerations for estimating groundwater residence times using radiocarbon in areas influenced by volcanic CO2.

Land surface temperature (LST) seems to be related to the temperature of shallow aquifers and the unsaturated zone thickness (∆Zuz). That relationship is valid when the study area fulfils certain characteristics: a) there should be no downward moisture fluxes in an unsaturated zone, b) the soil composition in terms of both, the different horizon materials and their corresponding thermal and hydraulic properties, must be as homogeneous and isotropic as possible, c) flat and regular topography, and d) steady state groundwater temperature with a spatially homogeneous temperature distribution. A night time Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image and temperature field measurements are used to test the validity of the relationship between LST and ∆Zuz at the Pampa del Tamarugal, which is located in the Atacama Desert (Chile) and meets the above required conditions. The results indicate that there is a relation between the land surface temperature and the unsaturated zone thickness in the study area. Moreover, the field measurements of soil temperature indicate that shallow aquifers dampen both the daily and the seasonal amplitude of the temperature oscillation generated by the local climate conditions. Despite empirically observing the relationship between the LST and ∆Zuz in the study zone, such a relationship cannot be applied to directly estimate ∆Zuz using temperatures from nighttime thermal satellite images. To this end, it is necessary to consider the soil thermal properties, the soil surface roughness and the unseen water and moisture fluxes (e.g., capillarity and evaporation) that typically occur in the subsurface.

The underlying hypothesis of this study was that pseudo-equilibrium and column testing conditions would provide the same sorbent ranking trends although the values of sorbents' performance descriptors (e.g. sorption capacity) may vary because of different kinetics and competition effects induced by the two testing approaches. To address this hypothesis, nano-enabled hybrid media were fabricated and its removal performances were assessed for two model contaminants under multi-point batch pseudo-equilibrium and continuous-flow conditions. Calculation of simultaneous removal capacity indices (SRC) demonstrated that the more resource demanding continuous-flow tests are able to generate the same performance rankings as the ones obtained by conducing the simpler pseudo-equilibrium tests. Furthermore, continuous overlap between the 98% confidence boundaries for each SRC index trend, not only validated the hypothesis that both testing conditions provide the same ranking trends, but also pointed that SRC indices are statistically the same for each media, regardless of employed method. In scenarios where rapid screening of new media is required to obtain the best performing synthesis formulation, use of pseudo-equilibrium tests proved to be reliable. Considering that kinetics induced effects on sorption capacity must not be neglected, more resource demanding column test could be conducted only with the top performing media that exhibit the highest sorption capacity.

The Talave tunnel (TT) is an infrastructure of a major water transfer from the Tajo river basin (center Spain) to the Segura river basin (SE Spain), crossing the Jucar river basin. The tunnel was drilled between 1969 and 1978. It is 32 km long, N/NW-S/SE oriented, has a maximum depth of 320 m, intersects several aquifers, and its southern stretch follows the eastern boundary of the Alcadozo aquifer. The TT drilling perturbed groundwater flow in two river basins, and the induced groundwater inlets generated social and administrative concern lasting until today. The main objectives of this paper are understanding the historical and current tunnel-massif hydrodynamic relationships, and deciphering the origin of groundwater inflow into the tunnel. The first objective was approached analyzing the discharge flow evolution since the drilling until 2016, together with old (1970s) and recent (2014–2017) piezometric data. For the second objective, hydrochemical and isotopic data were generated between 2014 and 2018 from discrete and integrated discharge to the tunnel. Attaining both goals benefited of recent studies on groundwater recharge and functioning in the Alcadozo aquifer. Discharge flows stabilized in the early 2000s. 340 hm3 were drained between 1969 and 2016, producing a piezometric drawdown between 15 and 120 m along the tunnel. The main inflow zones correspond to tectonic fractures concentrated in the middle and southern sections of the tunnel. The existence of a hydrogeological divide between the Jucar and the Segura river basins some 3 km to the N of the watershed divide implies that all groundwater comes from the Segura hydrogeological basin. The isotopes suggest that groundwater comes mainly from regional flow lines originated to the W of the tunnel, together with some local recharge. The effects of tunneling can be used to assess the impacts of imminent groundwater development planned by the Basin Authority.

Aquifers in permeable formations developed in high-mountain watersheds slow down the transfer of snowmelt to rivers, modifying rivers' flow pattern. To gain insight into the processes that control the hydrologic response of such systems the role played by groundwater in an alpine basin located at the southeastern part of the Iberian Peninsula is investigated. As data in these environments is generally scarce and its variability is high, simple lumped parameter hydrological models that consider the groundwater component and snow accumulation and melting are needed. Instead of using existing models that use many parameters, the Témez lumped hydrological model of common use in Spain and Ibero-American countries is selected and modified to consider snow to get a simplified tool to separate hydrograph components. The result is the TDD model (Témez-Degree Day) which is applied in a high mountain watershed with seasonal snow cover in Southern Spain to help in quantifying groundwater recharge and determining the groundwater contribution to the outflow. Average groundwater recharge is about 23% of the precipitation, and groundwater contribution to total outflow ranges between 70 and 97%. Direct surface runoff is 1% of precipitation. These values depend on the existence of snow. Results are consistent with those obtained with chloride atmospheric deposition mass balances by other authors. They highlight the important role of groundwater in high mountain areas, which is enhanced by seasonal snow cover. Results compare well with other areas. This effect is often neglected in water planning, but can be easily taken into account just by extending the water balance tool in use, or any other, following the procedure that has being developed., Grup d'Hidrologia Subterrànea, Universitat Politècnica de Catalunya, España, Instituto Geológico y Minero de España, España, Universidad Católica del Norte, Chile

Plastic debris have been shown to degenerate to particle sizes that can be transported in air, water, and food. Small particles are documented to enter and exit our bodies and translocate to and from some internal organs. Health effects on respiratory, hepatic, immune, and gastrointestinal systems have been reported in humans and other mammals in response to elevated particle or fiber exposures. These health effects differed by plastic type and size, and there was evidence of dose response for a few health endpoints. We conducted a systematic word search and reviewed published literature to identify microplastic and nanoplastic studies that quantified exposure via the ingestion, inhalation, and subcutaneous absorption (not dermal) exposure pathways; identified translocation, internal dose, and associations with health effects and markers related to exposures to specific sizes and types of plastics. We identified the data gaps in relating exposure data to health effects and biomarkers, most notably the lack of characterization of plastic particles and fibers smaller than 10 microns in most media.

Time series of environmental tracers (groundwater stable isotope composition, electrical conductivity and temperature) and concentration breakthrough curves of artificial tracers (uranine, eosine, amino-G and naphtionate) have been analyzed to characterize fast preferential and slow matrix in-transit recharge flows in the Paleocene-Eocene limestone aquifer of the Ordesa and Monte Perdido National Park, an alpine karst system drained by a water table cave, a rare hydrological feature in high mountain karst systems with similar characteristics. Snowmelt favors the areal recharge of the system. This process is reflected in the large proportion of groundwater flowing through the connected porosity structure of the karst aquifer, which amounts the 75% of the total system water discharge. From the perspective of water resources recovery, the water capacity of the fissured-porous zone (matrix) represents 99% of the total karst system storage. The volume associated to the karst conduits is very small. The estimated mean travel times are 9 days for conduits and 475 days for connected porosity. These short travel times reveal high vulnerability of the karst system to pollutants in broad sense and a great impact of climate change on the associated water resources.

Groundwater recharge is one of the key variables for aquifer management and also one of the most difficult to be evaluated with acceptable accuracy. This is especially relevant in semiarid areas, where the processes involved in recharge are widely variable. Uncertainty should be estimated to know how reliable recharge estimations are. Groundwater recharge has been calculated in the Alcadozo Aquifer System, under steady state conditions, at regional (aquifer) and sub-regional (spring catchment) scales applying different methods. The regional distribution of long-term average recharge values has been estimated with the chloride mass balance method using data from four rain stations and 40 groundwater samples covering almost the whole aquifer surface. A remarkable spatial variability has been found. Average annual recharge rates ranges from 20 to 243mmyear(-1) across the aquifer, with an estimated coefficient of variation between 0.16 and 0.38. The average recharge/precipitation ratio decreases from 34% in the NW to 6% in the SE, following the topographic slope. At spring-catchment scale, recharge has been estimated by modelling the soil water balance with the code Visual Balan 2.0. The results, calibrated with discharge data of the two main springs Liétor and Ayna, are 35.5 and 50mmyear(-1) respectively, with estimated coefficients of variation of 0.49 and 0.36. A sensitivity analysis showed that soil parameters influence the most the uncertainty of recharge estimations. Recharge values estimated with both methods and at two temporal and spatial scales are consistent, considering the regional variability obtained with the chloride method and the respective confidence intervals. Evaluating the uncertainties of each method eased to compare their relative results and to check their agreement, which provided confidence to the values obtained. Thus, the use of independent methods together with their uncertainties is strongly recommended to constrain the magnitude and to provide reliance to recharge estimations.

Intensive exploitation and continuous consumption of groundwater reserves (groundwater mining) have been real facts for decades in arid and semiarid areas. A summary of experience in the hydrogeological, economic, social and ethical consequences of groundwater intensive and mining exploitation in Gran Canaria and Tenerife Islands, in the Canarian Archipelago, is presented. Groundwater abstraction is less than recharge, but a significant outflow of groundwater to the sea cannot be avoided, especially in Tenerife, due to its younger volcanic coastal formations. Consequently, the intensive aquifer groundwater development by means of wells and water galleries (tunnels) has produced a groundwater reserve depletion of about 2km(3). Should current groundwater abstraction cease, the recovery time to close-to-natural conditions is from decades to one century, except in the mid and high elevations of Tenerife, where this recovery is not possible as aquifer formations will remain permanently drained by the numerous long water galleries. The socio-economic circumstances are complex due to a long standing history of water resources exploitation, successive social changes on each island, and well-established groundwater water trading, with complex relationships that affect water governance and the resulting ethical concerns. Gran Canaria and Tenerife are in an advanced groundwater exploitation stage and have a large water demand. They are good examples that allow drawing guidelines to evaluate groundwater development on other small high islands. After presenting the hydrogeological background, the socio-economic results are discussed to derive general knowledge to guide on water governance.

The time series of stable water isotope composition relative to IAEA-GNIP meteorological stations located in alpine zones are analyzed in order to study how the amplitude of the seasonal isotopic composition of precipitation (Aδ) varies along a vertical transect. A clear relationship between Aδ and local evaporation is obtained, with slopes of -0.87 ‰/100mm/yr and -7.3 ‰/100mm/yr for Aδ(18)O and Aδ(2)H, respectively. When all sampling points of the vertical transect receive the same moisture sources, then a linear relationship between Aδ and elevation is obtained, with vertical gradients of 0.16 ‰/100mm/yr and 1.46 ‰/100mm/yr forAδ(18)O and Aδ(2)H, respectively.

Laguna Tuyajto is a small, shallow saline water lake in the Andean Altiplano of northern Chile. In the eastern side it is fed by springs that discharge groundwater of the nearby volcanic aquifers. The area is arid: rainfall does not exceed 200mm/year in the rainiest parts. The stable isotopic content of spring water shows that the recharge is originated mainly from winter rain, snow melt, and to a lesser extent from some short and intense sporadic rainfall events. Most of the spring water outflowing in the northern side of Laguna Tuyajto is recharged in the Tuyajto volcano. Most of the spring water in the eastern side and groundwater are recharged at higher elevations, in the rims of the nearby endorheic basins of Pampa Colorada and Pampa Las Tecas to the East. The presence of tritium in some deep wells in Pampa Colorada and Pampa Las Tecas indicates recent recharge. Gas emission in recent volcanoes increase the sulfate content of atmospheric deposition and this is reflected in local groundwater. The chemical composition and concentration of spring waters are the result of meteoric water evapo-concentration, water-rock interaction, and mainly the dissolution of old and buried evaporitic deposits. Groundwater flow is mostly shallow due to a low permeability ignimbrite layer of regional extent, which also hinders brine spreading below and around the lake. High deep temperatures near the recent Tuyajto volcano explain the high dissolved silica contents and the δ(18)O shift to heavier values found in some of the spring waters. Laguna Tuyajto is a terminal lake where salts cumulate, mostly halite, but some brine transfer to the Salar de Aguas Calientes-3 cannot be excluded. The hydrogeological behavior of Laguna Tuyajto constitutes a model to understand the functioning of many other similar basins in other areas in the Andean Altiplano.

Lead isotope ratios and lead (Pb) levels were analyzed in 33 individuals from a forgotten cemetery at the Colorado Mental Health Institute at Pueblo, Colorado dating to 1879-1899. Isotopic ratios from healing bone fractures, cortical bone, and tooth dentine provide information about sources of Pb exposures over a range of time that illuminates individual's life histories and migration patterns. Historical records and Pb production data from the 19th century were used to create a database for interpreting Pb exposures for these African, Hispanic and European Americans. The analysis of these individuals suggests that Pb exposure noticeably impacted the mental health of 5-10% of the asylum patients in this frontier population, a high number by standards today, and that differences exist in the three ancestral groups' exposure histories.