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Different water sources can contribute to plant transpiration in Alpine environments, such as rainfall, snowmelt, irrigation and/or stream waters that are temporarily stored in the vadose and saturated zones. Particularly, the proportion of water uptake from different soil depths can strikingly differ depending on the species and the local environmental conditions such as the availability of freshwater resources, and local climatic and pedological settings.We aim at estimating the relative contributions of different water sources (i.e., soil water at various depths and groundwater) to tree transpiration with the use of stable water isotopes. Our work is part of a wider national project (WATZON: WATer mixing in the critical ZONe) studying the relationship between plants, soil and water in contrasting natural and semi-natural environments of Italy. Here we report the results of monitoring activities in two different ecosystems in South-Tyrol (Eastern Italian Alps): an apple orchard growing on a deep (>2.5 m) sandy soil of the Adige floodplain (Binnenland), and a sub-alpine conifer forest located on steep slopes with a shallow (10-60 cm) skeletal soil (Mazia, 2000 mt a.s.l.), where we selected European larch (Larix decidua) as a model-species. Water (precipitation, stream water, groundwater), soil at different depths and twigs samples were collected fortnightly from May to November 2020, and weather conditions (automatic stations), soil parameters (moisture and temperature) at different depths and sapflow were continuously recorded over the entire period.At both locations, precipitation waters had a heavier isotopic composition than stream water and groundwater, that did not show any significant difference between each other in terms of isotopic signature. While all these potential water sources plotted on the local meteoric water line, shallow soil water samples (5-15 cm) deviated from it revealing a stronger and more variable evaporative fractionation when compared with those of deeper soil (25-65 cm). Xylem water samples from apple trees at Binnenland overlapped with soil water samples, more consistently at 10-30 cm depths. This water mostly derived from infiltrated rainwater but with a non-negligible contribution from groundwater during July and August. In contrast, xylem water from larch trees at Mazia plotted on the local meteoric water line, and had an isotopic composition more similar to that of precipitation than soil water even for samples collected after several days of drying out. As sapflow measurements of larches revealed a continuous transpiration, it is unlikely that trees took up water only soon after precipitation events. Instead, we hypothesize that larches at Mazia likely rely on a water pool which is different from the soil (e.g., rock moisture).These contrasting ecohydrological systems reveal different strategies of water use by dwelling plants in natural and anthropic systems, showing a distinct sensitivity and resilience to changing climate.

Understanding the dynamics and sources of root water uptake in agricultural systems is becoming increasingly important for implementing efficient and sustainable water resources management and, at the same time, for optimizing crop yield and quality under changing climatic conditions. In this work, we adopted the stable isotope approach to investigate the water sources accessed by apple trees in two orchards growing in the upper Etsch/Adige valley (South Tyrol, Eastern Italian Alps). We tested the general hypothesis that soil water, composed of a mixture of rain and irrigation water, was the main source for tree transpiration but that river water and groundwater mixed with soil water and contributed to root uptake for trees growing close to the river and with higher water table. Our results revealed that apple trees during the 2015 and 2016 growing seasons relied mostly on soil water present in the upper 20-40 cm of soils, with an apparently negligible contribution of groundwater and river water, irrespective of the field position across the valley bottom. The isotopic composition of xylem water did not reflect the one of irrigation water (and neither that of groundwater) but rather of rainfall and throughfall, as well as that of soil water. We related this “hidden” tracer signature of irrigation water to the effect of soil evaporation that strongly modified its original isotopic composition: irrigation and rain water infiltrated into the soil and mixed with isotopically fractionated soil water, and trees took up a mixture of water with different isotopic composition compared to the one of the original irrigation source. This work contributes to improve the understanding of water uptake strategies in Alpine apple orchards and paves the way for further analysis on the proportion of irrigation and rain water used by apple trees in mountain agroecosystems.

The Italian initiative WATZON (WATer mixing in the critical ZONe) is a network of instrumented sites, bringing together six pre-existing long-term research observatories monitoring different compartments of the Critical Zone - the Earth's permeable near-surface layer from the tops of the trees to the bottom of the groundwater. These observatories cover different climatic and physiographic characteristics over the country, providing information over a climate and eco-hydrologic transect connecting the Mediterranean to the Alps. With specific initial scientific questions, monitoring strategies, databases, and modeling activities, the WATZON observatories and sites is well representative of the heterogeneity of the critical zone and of the scientific communities studying it. Despite this diversity, all WATZON sites share a common eco-hydrologic monitoring and modelling program with three main objectives:1) assessing the description of water mixing process across the critical zone by using integrated high-resolution isotopic, geophysical and hydrometeorological measurements from point to catchment scale, under different physiographic conditions and climate forcing;2) testing water exchange mechanisms between subsurface reservoirs and vegetation, and assessing ecohydrological dynamics in different environments by coupling the high-resolution data set from different critical zone study sites of the initiative with advanced ecohydrological models at multiple spatial scales;3) developing a process-based conceptual framework of ecohydrological processes in the critical zone to translate scientific knowledge into evidence to support policy and management decisions concerning water and land use in forested and agricultural ecosystems.This work provides an overview of the WATZON network, its objectives, scientific questions, and data management, with a specific focus on existing initiatives for linking data and models based on WATZON data.

Understanding discharge and solute responses is pivotal for water resources management and pollution mitigation measures. The few studies that have analysed concentration-discharge relations using high temporal resolution tracer data collected during rainfall-runoff events have shown that these relations may vary for different events and depend on season, event characteristics or antecedent wetness conditions. In this study, we used hydrometric and tracer data (stable isotopes, major ions and electrical conductivity (EC)) to i) compare the concentration-discharge relations for different tracers, ii) characterize the hysteretic relations between discharge and tracer concentrations at the event timescale, and iii) determine whether the changes in hysteresis can be explained by event characteristics.Data collection was carried out in the Ressi catchment, a 2-ha forested watershed in the Italian pre-Alps. The catchment is characterized by high seasonality in runoff response, due to the seasonality in rainfall (high in fall) and evapotranspiration (high in summer). Discharge and rainfall have been measured continuously since August 2012. Stream water, precipitation, shallow groundwater and soil water samples were collected for tracer analyses during 20 rainfall-runoff events between September 2015 and August 2018. All samples were analyzed for EC, isotopic composition (2H and 18O) and major ion concentrations. To investigate the possible controls on concentration-discharge relations, we determined the main characteristics (e.g., total event rainfall, rainfall intensities, antecedent soil moisture and depth to water table, runoff coefficient) for each selected rainfall-runoff event.The EC, calcium, magnesium, sodium and sulfate concentrations in stream water decreased during rainfall events, due to the dilution by rain water. The concentration-discharge relations for these tracers with a dilution behavior were stronger and more significant than for the tracers that were mobilized during the event. Interestingly, nitrate, potassium and chloride, concentrations sometimes increased at the onset of events, likely due to a rapid flushing of solutes from the dry parts of the stream channel and the riparian area, and then decreased during the event. These temporal dynamics in solute concentrations resulted in different hysteretic relations with discharge. Clockwise loops (i.e., discharge peaked later than the tracer concentrations) were common for the isotopes, chloride and potassium, whereas anti-clockwise hysteresis loops were more typical for EC, magnesium, calcium, sulfate, sodium and nitrate. A preliminary correlation analysis suggests that event characteristics alone cannot explain the changes in hysteresis, except for the hysteresis area for the relations between discharge and calcium concentration that depends on the magnitude of the rainfall event (i.e., the larger the rainfall amount and the runoff coefficient, the smaller the hysteresis loop). These results highlight the importance of the first flush and indicate that runoff processes and solute sources can change when the catchment becomes wetter and connectivity of the hillslopes to the stream increases. Keywords: concentration-discharge relation; major ions; electrical conductivity; stable isotopes; hysteresis; forested catchment.

Plant transpiration is a main component of the global water cycle and plays a key role in regulating ecohydrological process. Stable isotopes of oxygen and hydrogen are often used for the identification and quantification of plant water sources in ecohydrology. However, the isotopic tracing technique assumes that the isotopic signal in the water taken up by the plants remains unaltered during uptake at the soil-roots interface and transport to the distal twigs, i.e., isotopic fractionation does not occur during the water uptake and along the transport pathway. Nevertheless, recent studies showed that isotopic fractionation can occur under different environmental conditions. In this study, we performed a simple experiment with two olive (Olea europaea) trees utilizing labelled water to test isotopic fractionation of plant water during uptake and transport within the plants under controlled conditions. In addition, we performed the cryogenic vacuum distillation in two different laboratories to examine any possible effects of the extraction system on the isotopic composition of plant water extracts.We set up the olive trees in pots inside a glasshouse and measured sap flow rates with Granier thermal dissipation probe, and shallow soil moisture by using a portable soil moisture probe. Air temperature, global solar radiation, and relative humidity were measured by a weather station installed inside the glasshouse nearby the olive trees. We irrigated the two plants with water of known isotopic composition and sampled the twigs, wood cores, roots, and soils at different depths (0-5, 5-15, and 15-25 cm). We extracted plant and soil waters by means of cryogenic vacuum distillation performed in two different laboratories.Our results showed that the plant water samples reflected the isotopic signature of labelled water and mobile soil water, suggesting no isotopic fractionation during water transport. No significant differences were detected for twigs and wood cores extracted from distinct sections of the tree. However, only significant differences were obtained between plant tissue water (twigs, cores) and cryogenically-extracted deep soil water (i.e., >15 cm depths). Furthermore, we found no significant effects of the two cryogenic extraction systems on the isotopic composition of water extracts. Our results indicate that isotopic fractionation might not occur during root water uptake and transport processes in olive trees, at least under the specified experimental conditions, validating the conventional isotope-tracing approach. Further work both in the field and under controlled conditions, and on different plant species, is needed to check for this consistency, as well as testing other plant water extraction methods. Keywords: olive tree; stable isotope analysis; plant water; cryogenic vacuum distillation; fractionation; labelled water.

Obtaining reliable estimates of isotopic composition of xylem water transported in tree stems is crucial for ecohydrological studies. In most tree species xylem consists of two physiologically different parts, sapwood and heartwood. The former functions as the flowpath for sap flow, whereas the latter does not conduct water and provides mechanical support to the stem. However, some studies highlighted that water stored in heartwood might sustain transpiration by providing water during dry periods. Therefore, assessing how the isotopic composition in sapwood and heartwood compartments changes over time is critical to explain tree hydraulic.Typically, studies rely on wood cores from the tree trunk to isotopically characterize xylem water in order to assess water sources for tree use (e.g., soil water from different depths, groundwater, stream water or a mixture of those), and only few studies specified which functional portion of the wood was sampled. There is currently a lack of knowledge on the possible isotopic difference between heartwood and sapwood potentially leading to uncertainties on the origin of the extracted water.In the present study, we investigate four forest species characterised by different xylem anatomy, wood density, and timing of physiological activity to evaluate the degree of differentiation in isotopic composition between sapwood and heartwood.We carried out biweekly sampling campaigns over one growing season (March-October 2020) in a central European forest (Luxembourg) to assess sapwood and heartwood isotopic composition and water content of European beech (Fagus sylvatica), sessile oak (Quercus petraea), douglas fir (Pseudotsuga menziesii), and spruce (Picea abies).Preliminary results showed a temporal variation in isotopic composition both in sapwood and heartwood for all investigated species. In conifers, we found a stronger difference in isotopic composition and water content between sapwood and heartwood compared to broadleaved species suggesting a larger degree of compartmentalization. Heartwood displays consistently heavier oxygen delta values compared to sapwood in all species whereas sapwood shows heavier hydrogen delta values compared to heartwood only in conifers. These preliminary results suggest that the occurrence of potential mixing between older water stored in the heartwood and newly uptake water flowing in the sapwood should be taken into account in tree water uptake studies.

Plant transpiration is the dominant water flux in the global terrestrial water balance and a key process in the hydrological sciences. Stable isotopes have contributed greatly to this understanding but one difficult assumption for plant water source quantification using hydrogen and oxygen isotopes is that no isotopic fractionation occurs during water uptake and transport within the plant. Here we present a simple glasshouse experiment with two potted olive trees to test isotopic fractionation. We irrigated the trees with labelled water and cryogenically extracted water from twigs, cores and roots. We found no significant differences in the isotopic composition of water extracted from wood cores and twigs in distinct parts of the trees as they reflected the signature of labelled water. However, significant differences were obtained between plant water and deep soil water. Our results suggest no isotopic fractionation in olive trees, under the specific experimental conditions, validating the traditional isotope-tracing approach.

This study investigates changes in the hydrologic regime of the Chitral River, Hindukush–Karakoram–Himalayan (HKH) region, Pakistan. Different statistically based methods were used to assess climate change-induced hydrologic alterations that can possibly impact aquatic habitat in the study region. The hydrological model Hydrologiska Byråns Vattenbalansavdelning (HBV) was calibrated, validated, and applied to predict streamflow in the Chitral River basin. The HBV model was forced with the ensemble of four general circulation models under different representative concentration pathway emission scenarios to generate future streamflow under climate change conditions in the basin for the mid-twenty-first century. The results of this study show that hydrologic regimes in the study area, expressed by the magnitude, duration, frequency, timing, and rate of streamflow, are likely to alter in the future. Positive (i.e., with increased frequency) hydrologic alteration is projected for most flow parameters under all scenarios for the 2021–2050 period compared with values observed during the historical period (1976–2005). These hydrologic alterations might have impacts on fish and migratory bird species in the study area. This research can be helpful in providing practical information for more effective water resources and aquatic ecosystem management in the HKH region. HIGHLIGHTS Investigation of changes in the hydrologic regime of the Chitral River.; Employment of IHA and RVA methods to evaluate riverine ecosystem health.; Hydrological modeling using HBV-light to generate future streamflow.; Assessment of climate change impacts on different streamflow characteristics.; Analysis of streamflow changes and their relationship with aquatic habitat.

Involvement of the nervous system with sarcoidosis is seen clinically in approximately 5-15% of cases. In most cases, lesions are localized to the leptomeninges and cranial nerves, and rarely to the pituitary gland, leading to endocrinologic abnormalities. We report on an original clinical case demonstrating the effectiveness of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) scan in the diagnosis and monitoring of systemic sarcoidosis with probable pituitary involvement.

Recent tracer-based studies using stable isotopes of hydrogen and oxygen showed that different methods for extracting water from plant tissues can return different isotopic compositions due to the presence of organic compounds and because they extract different plant water domains. One of the most used methods to extract plant water is the cryogenic vacuum distillation (CVD), which tends to extract total plant water. Conversely, the Scholander-type pressure chamber (SPC), which is commonly used by tree physiologists to measure water potential in plant tissues and determine plant water stress, is expected to extract only the more mobile plant water (i.e., xylem and inter-cellular water). However, only few studies reported the application of SPC to extract plant water for isotopic analyses, and therefore, inter-method comparisons between SPC and CVD are of great value. In this work, we analyzed the variability in the isotopic composition of plant water extracted by SPC and CVD, also considering the potential variability in the isotopic signature of the plant water extracted by CVD from various tissues (i.e., leaves, twig without bark, twig with bark, twig close to the trunk of the tree, and wood core) and from different plant species (i.e., alder, apple, chestnut, and beech). The extraction of plant water by SPC is simple, can be carried out in the field, and it does not require specific laboratory work as in the case of CVD. However, the main limitation of SPC is the very small water volume that can be extracted from the lignified twigs under water stress conditions compared to CVD. Our results indicated that plant water extracted by SPC and CVD were significantly different. The difference in the isotopic composition obtained by the two extraction methods was smaller in the beech samples compared to alder, apple, and chestnut samples. The isotopic signature of alder, apple, and chestnut plant water extracted by SPC was more enriched in δ2H and δ18O, respectively, than the samples obtained by CVD. We conclude that plant water extraction by SPC is not an alternative for CVD as SPC mostly extracts the mobile plant water, whereas CVD tends to retrieve all water stored in the sampled tissue from both living and dead cells. However, studies aiming to quantify the relative contribution of the soil water sources to transpiration should rely more on the isotopic composition of xylem water (which is theoretically sampled by SPC) than the isotopic composition of total plant water (sampled by CVD), which also contains a fraction of water that could be stored in plant tissues for a longer time.

Effective water resource management can benefit from estimations of when water entered the catchment and how long it takes to flow to the outlet. In this context, the so-called young water fraction (Fyw) based on seasonal input and output tracer cycles is becoming increasingly used as robust tool to compare the hydrological function of catchments. In seasonally cold environments, this Fyw estimation is complicated by the fact that a large part of the precipitation will be in the form of snow, will be stored before melting and becoming available as water, resulting in a distinct winter low flow and summer high flow season. Nevertheless, Fyw might enclose extremely interesting information in such environments since they incorporate the relationship between late summer and autumn flow and the previous winter’s snow input. However, most currently available methods for Fyw estimation do not explicitly account for the seasonal shift of water input from snow. Therefore, we propose a novel framework to explicitly account for this “snowmelt” delay in Fyw and explore related uncertainties using experimental data from three high-elevation Alpine catchments, the Vallon de Nant in Switzerland, and the Noce Bianco at Pian Venezia and the Bridge Creek Catchments in Italy. Experimental data from these environments expose some limitations of existing methods in accounting for unavoidable sampling inconsistencies. Using our method that explicitly accounts for snowmelt, we found extremely low Fyw in these three Alpine catchments: 6%, 13%, and 31%. In this contribution, we will present our method in detail and highlight emerging challenges and implications of the Fyw estimation.

In the face of current global warming conditions, temperate forest ecosystems are expected to be strongly affected by temperature increase and more frequent and intense water shortage. This leads to severe stress for forest vegetation in many temperate systems. Therefore, understanding the vegetation water use in temperate forests is urgently needed for more effective forest management strategies. Root water uptake (RWU) is a species-specific trait (tree physiology and root architecture) and its spatio-temporal patterns are controlled by a range of site-specific (e.g., topography, geology, pedology) and meteorological factors (e.g., temperature, soil humidity, rainfall.In the present study, we use stable water isotopologues as ecohydrological tracers combined with continuous measurement of hydrometeorological (weather variables, groundwater levels, soil moisture, streamflow) and physiological (sap flow, radial stem growth) parameters to investigate the spatio-temporal dynamics of water uptake for beech (Fagus sylvatica L.) and sessile oak (Quercus petraea (Matt.) Liebl) trees along a hillslope in a Luxemburgish catchment.Fortnightly field campaigns were carried out during the growing season (April-October) 2019 to sample water from xylem, soil water at different depths, groundwater, stream water, and precipitation. Soil water isotopic composition and xylem water were extracted via cryogenic distillation. Grab sampling was performed for the other water pools. The isotopic composition was determined through laser spectroscopy and mass spectrometry (for xylem samples only).From preliminary results, the isotopic composition of xylem water shows a marked seasonal variability suggesting a plasticity in RWU or a change in the isotopic composition of the water pools over the growing season. Moreover, beech and oak trees exhibit different uptake strategies when water supply is low. Within the range of observed groundwater variation topography does not play a statistically significant role on RWU.

The bi-directional ecohydrological interactions between forest dynamics and catchment hydrological response in Mediterranean forest ecosystems remain poorly conceptualized. Understanding the effect of tree water uptake and transpiration patterns on how catchments store and release water and, vice versa, on how catchment water availability affects tree physiological response is of paramount importance for forest and water resource management. This is crucial in the light of the predicted prolonged drought periods that will exacerbate the dry summer spells that characterize Mediterranean areas. In order to address these pressing issues, a new experimental mountain forested catchment for interdisciplinary ecohydrological research has been recently implemented in the Tuscan Apennines (Italy). The catchment size is 2 km2 and elevation ranges from 650 to 1280 m a.s.l.. Forest covers more than 95% of the area, and the main tree species are beech and oak trees, with a much smaller proportion of conifers. Mean annual precipitation is around 1180 mm. Instrument installation is currently in progress and supported by two research projects (run in parallel in Italy and Luxembourg). By spring 2020, the catchment is expected to host the following equipment: one weather station plus one additional rain gauge, including a rainfall collector for isotope analysis; four stream gauges at different spatial scales (from a 2-ha headwater subcatchment to the catchment outlet) including continuous electrical conductivity measurements; three groundwater wells (ranging from 2 to 5 m depth) equipped with water level and electrical conductivity loggers; a network of soil moisture sensors at different depths; stemflow collectors; rain totalizers for manual throughfall measurements; a network of innovative multi-parametric sensors mounted on individual beech trees for continuous measurement (logging to cloud) of physiological and micro-meteorological parameters (sap flow, stem radial growth, canopy light transmission, stem wood temperature and humidity, 3D position over time, and air temperature and relative humidity). Preliminary data collected in 2019 show a marked seasonality of stream runoff, with low runoff coefficients in summer (

Improving the efficiency and sustainability in water resources management in agricultural and agroforestry systems is becoming increasingly important in the light of the increasing pressure on agro-food production due to the growing world population growth and the changing climatic conditions. In this context, achieving an accurate quantification of the proportions of different water sources (including irrigation) taken up by plants has important ecological and economic implications for water saving and utilization. Stable isotopes of hydrogen and oxygen in the water molecule are powerful and, nowadays, affordable tracers that can greatly help to identify and quantify the seasonal water uptake patterns by plants. This tool is largely adopted in natural systems (e.g., in ecohydrological applications in forested environments) but has not been fully exploited in agricultural and agroforestry ecosystems. Here, we outline the advantages and limitations of this technique and report some examples on how it can support more traditional approaches to understand root water uptake dynamics in agricultural and agroforestry systems. Finally, we present a vision for future challenges and new research lines using isotope tracers to investigate crop water use.

Stable water isotopes have proven to be useful tracers to determine the origin of water taken up by plants, quantify the relative contributions of water sources to stream runoff and investigate water flow paths. However, the presence of different water pools in a catchment and soil water allocation complicates our understanding of water cycling, and calls for research on processes governing soil water movement and storage, as well as interactions between soil and plants.In this study, we used isotopic data from a forested catchment in the Italian pre-Alps to i) investigate the spatial and temporal variability of the isotopic signature of various water sources, and ii) determine which waters are used by beech and chestnut trees in the study area. Ecohydrological and hydrometeorological monitoring took place in the 2.4-ha Ressi catchment (Northern Italy). Elevations range from 598 to 721 m a.s.l., while average slope is 31°. Average annual precipitation is about 1695 mm, while average annual temperature is 9.7 °C. The entire catchment is covered by deciduous forest, with beech, chestnut, hazel and maple as the main tree species.Water samples for isotopic analysis were taken monthly from bulk precipitation, approximately bi-weekly from stream water, groundwater and soil water by two suction lysimeter cups in the riparian zone. Bulk soil water samples and twigs for xylem water extraction by cryogenic vacuum distillation were collected starting in June, 2017. All water samples were analysed by laser spectroscopy, except xylem water that was analysed by mass spectrometry. Stream water, groundwater and soil water extracted by suction lysimeters were isotopically similar to precipitation and aligned to the local meteoric water line. Bulk soil water obtained by cryogenic vacuum distillation showed an evaporation signature, especially on the hillslope where soil moisture was lower and soil water had been extracted by suction lysimeters only during or just after a large rainfall event. This indicates that soil water sampled by suction lysimeters and extracted by cryogenic vacuum distillation is stored differently in the soil layers due to the different soil tension, and hillslopes tend to store less mobile soil water compared to the riparian zone. At greater depths, bulk soil water extracted by cryogenic vacuum distillation was slightly less evaporated and less enriched in heavy isotopes compared to soil water extracted from shallower layers. The isotopic composition of xylem water had a large temporal and tree-species variability, with chestnut xylem water samples more enriched in heavy isotopes than samples obtained from beech trees. Xylem water was more similar to soil water obtained by cryogenic vacuum distillation, suggesting that in the study area trees likely use more bulk soil water than the mobile soil water, groundwater and stream water. Keywords: stable water isotopes; soil water; xylem water; forested catchment.

Water levels in streams and aquifers often exhibit daily cycles during rainless periods, reflecting diurnal extraction of shallow groundwater by evapotranspiration (ET) and, during snowmelt, diurnal additions of meltwater. These cycles can potentially aid in understanding the mechanisms that couple solar forcing of ET and snowmelt to variations in streamflow. Here we analyze three years of 30-minute solar flux, sap flow, stream stage, and groundwater level measurements at Sagehen Creek and Independence Creek, two snow-dominated headwater catchments in California's Sierra Nevada mountains. During snow-free summer periods, daily cycles in solar flux are tightly correlated with variations in sap flow, and with the rates of water level rise and fall in streams and riparian aquifers. During these periods, stream stages and riparian groundwater levels decline during the day and rebound during the night. During snowmelt, daily cycles in solar flux have the opposite effect, with stream stages and riparian groundwater levels rising during the day in response to snowmelt inputs, and declining at night as the riparian aquifer drains. The mid-day peak in solar flux coincides with the fastest rates of water level rise and decline (during snowmelt and ET-dominated periods, respectively), not with the maxima or minima in water levels themselves. A simple conceptual model explains these temporal patterns: streamflows depend on riparian aquifer water levels, which integrate snowmelt inputs and ET losses over time, and thus will be phase-shifted relative to the peaks in snowmelt and evapotranspiration rates. The highest and lowest riparian water levels (for snowmelt and ET cycles, respectively) will not occur at mid-day when the solar forcing is strongest, but rather in the late afternoon when the solar forcing declines enough that the riparian aquifer transiently achieves mass balance. Thus, although the lag between solar forcing and water level cycles is often interpreted as a travel-time lag, our analysis shows that it is predominantly a dynamical phase lag, at least in small catchments. Furthermore, although daily cycles in streamflow have often been used to estimate ET fluxes, our simple conceptual model demonstrates that this is infeasible unless the time constant of the riparian aquifer can be determined. As the snowmelt season progresses, snowmelt forcing of groundwater and streamflow weakens and evapotranspiration forcing strengthens. Because these two forcings have opposite phases, groundwater and stream level variations reflect the balance between them. The relative dominance of snowmelt vs. ET can be quantified by the diel cycle index, the correlation coefficient between the solar flux and the rate of rise or fall in streamflow or groundwater, which will be close to +1 and 1 when water level cycles are dominated by snowmelt and ET, respectively. When the snowpack melts out at an individual location, the diel cycle index in the local groundwater shifts abruptly from snowmelt-dominated cycles to ET-dominated cycles. Streamflow, however, integrates these transitions over the drainage network. Thus the transition in the streamflow diel cycle index begins when the snowpack melts out near the gauging station, and ends, months later, when the snowpack melts out at the top of the basin and the entire drainage network becomes dominated by ET cycles. During this long transition, Sagehen Creek's upper reaches exhibit snowmelt cycles at the same time that its lower reaches exhibit ET cycles, implying that snowmelt signals generated in the upper basin are overprinted by ET signals generated lower down in the basin. Sequences of Landsat images show that the gradual springtime transition in the diel cycle index mirrors the springtime retreat of the snowpack to higher and higher elevations, and the corresponding advance of photosynthetic activity across the basin. Furthermore, trends in the catchment-averaged MODIS enhanced vegetation index (EVI2) correlate closely with both the late springtime shift from snowmelt to ET cycles and the autumn shift back toward snowmelt cycles. The data and analyses presented here illustrate how streams can act as mirrors of the landscape, integrating physical and ecohydrological signals across their contributing drainage networks.

Funding Information Fondazione Cassa di Risparmio di Padova e Rovigo. Grant Number: Bando Starting Grants 2015

In Mediterranean area (MA), floods are, after droughts, the most dangerous meteorological hazard causing severe damages of manmade infrastructures, produce large loss of lives, and adversely affect the opportunities for socio-economic development of MA countries. MA is characterized by a relatively high number of flash floods (FFs) and floods occurring in small catchments normally triggered by deep convective systems associated with intense precipitation with a limited areal extent and high initial wetness conditions. For these reasons, the understating of the role of rainfall and soil moisture as well as the techniques available for their monitoring is particularly important. In this chapter, we review the most important studies carried out on floods in MA, which focuses on (1) the importance of the rainfall and soil moisture in the triggering and evolution of these events; (2) the monitoring techniques and models available to estimate these two variables along with their operational use for their prediction.

Springs play a key role in the hydrology of mountain catchments and their water supply has a considerable impact on regional livelihood, biodiversity, tourism, and power generation. However, there is still limited knowledge of how rain and snow contribute to the recharge of Alpine springs. This study presents a four-year investigation of stable isotopes in precipitation and spring water at the scale of a 240 km2 wide dolomitic massif (Dolomites, Italian Alps) with the aim of determining the proportions of snowmelt and rain in spring water and to provide insights on the variability of these contributions in space and time. Four precipitation sampling devices were installed along a strong elevation gradient (from 725 to 2660 m a.s.l.) and nine major springs were monitored seasonally. The monitoring period comprised three extreme weather conditions, i.e., an exceptional snowpack melting period following the highest snowfall in 30 years, an intense precipitation event (386.4 mm of rain in 48 h), and one of the driest periods ever observed in the region. Isotope-based mixing analysis revealed that rain and snowmelt contributions to spring water were noticeably variable, with two main recharge time windows: a late spring&ndash, summer snowmelt recharge period with an average snowmelt fraction in spring water up to 94 &plusmn, 9%, and a late autumn&ndash, early winter period with a rain fraction in spring water up to 68 &plusmn, 17%. Overall, during the monitoring period, snowmelt produced high-flow conditions and sustained baseflow more than rain. We argue that the seasonal variability of the snowmelt and rain fractions during the monitoring period reflects the relatively rapid and climate-dependent storage processes occurring in the aquifer. Our results also showed that snowmelt fractions in spring water vary in space around the mountain group as a function of the elevation of their recharge areas. High-altitude recharge areas, above 2500 m a.s.l., are characterized by a predominance of the snowmelt fraction (72% &plusmn, 29%) over the rain contribution. Recharge altitudes of approximately 2400 m a.s.l. also show a snow predominance (65 &plusmn, 31%), while springs recharged below 2000 m a.s.l. are recharged mostly from rain (snowmelt fraction of 46 &plusmn, 26%). Results from this study may be used to develop more accurate water management strategies in mountain catchments and to cope with future climate-change predictions that indicate a decline in the snow volume and duration in Alpine regions.

The Ordinary Least Squares (OLS) regression is the most common method for fitting the δ2H-δ18O relationship. Recently, various studies compared the OLS regression with the Reduced Major Axis (RMA) and Major Axis (MA) regression for precipitation data. However, no studies have investigated so far the differences among the OLS, RMA, and MA regressions for water types prone to evaporation, mixing, and redistribution processes. In this work, we quantified the differences in terms of slopes and intercepts computed by the OLS, RMA, and MA methods for rainfall, snow and ice, stream, spring, groundwater, and soil water, and investigated whether the magnitude of such differences is significant and dependent on the water type, the datasets statistics, geographical or climatic characteristics of the study catchments. Our results show that the differences between the regression methods were largest for the isotopic data of some springs and some stream waters. Conversely, for rainfall, snow, ice, and melt waters datasets, all the differences were small and, particularly, smaller than their standard deviation. Slopes and intercepts computed using the different regression methods were statistically different for stream water (up to 70.4%, n = 54), followed by groundwater, springs, and soil water. The results of this study indicate that a thorough analysis of the δ2H-δ18O relationship in isotope hydrology studies is recommended, as well as considering the measurement errors for both δ2H and δ18O, and the presence of outliers. In case of small measurement errors and no significant differences between the slopes computed through the three methods, we suggest the application of the widely used OLS regression. Conversely, if the computed slopes are significantly different, we recommend investigating the possible reasons for such discrepancies and prefer the RMA over the MA approach, as the latter tends to be more sensitive to data with high leverage (i.e., data points with extreme δ18O values).

Agricultural terraces are often subject to degradation issues related to water movement. A better understanding of the main hydrological processes that govern surface and subsurface water flow pathways and that are responsible for terrace failure and dry-stone wall collapse is essential for appropriate water resource management and rural landscape maintenance in terraced areas. However, a clear conceptualization of different hydrological functioning related to wall instability issues is still missing. In this study we monitored a terrace system in a hilly site of central Italy cultivated with vineyards. We adopted a multidisciplinary approach based on soil analysis, different geophysical techniques, hydrological monitoring, high-resolution grid terrain analysis and field experiments (infiltration and flooding tests) aiming to i) obtain new information of terrace soil and subsoil structure; ii) test the hypothesis on wall instability based on the formation of preferential flow and water accumulation behind the wall; and iii) develop a conceptual model of water circulation in agricultural terraces. Our results indicate that terrace soil was highly heterogeneous including discontinuities and piping systems that facilitated a rapid infiltration and the development of fast subsurface flow. Groundwater rise did not occur, as observed in other terraced sites, but infiltrated water accumulated behind dry-stone walls, increasing pore water pressure and inducing wall bulging and instability. Our findings provided new field evidences of water circulation and led to the definition of a novel paradigm of hydrological functioning of farming terraced systems for addressing more efficient management and maintenance issues in these vulnerable landscapes.

Multiple water sources and the physiographic heterogeneity of glacierized catchments hamper a complete conceptualization of runoff response to meltwater dynamics. In this study, we used environmental tracers (stable isotopes of water and electrical conductivity) to obtain new insight into the hydrology of glacierized catchments, using the Saldur River catchment, Italian Alps, as a pilot site. We analysed the controls on the spatial and temporal patterns of the tracer signature in the main stream, its selected tributaries, shallow groundwater, snowmelt and glacier melt over a 3-year period. We found that stream water electrical conductivity and isotopic composition showed consistent patterns in snowmelt-dominated periods, whereas the streamflow contribution of glacier melt altered the correlations between the two tracers. By applying two- and three-component mixing models, we quantified the seasonally variable proportion of groundwater, snowmelt and glacier melt at different locations along the stream. We provided four model scenarios based on different tracer signatures of the end-members; the highest contributions of snowmelt to streamflow occurred in late spring–early summer and ranged between 70 and 79 %, according to different scenarios, whereas the largest inputs by glacier melt were observed in mid-summer, and ranged between 57 and 69 %. In addition to the identification of the main sources of uncertainty, we demonstrated how a careful sampling design is critical in order to avoid underestimation of the meltwater component in streamflow. The results of this study supported the development of a conceptual model of streamflow response to meltwater dynamics in the Saldur catchment, which is likely valid for other glacierized catchments worldwide.

Diagnosis of idiopathic mediastinal fibrosis was done by exclusion in a 54-year-old woman with dyspnoea, chest pain, cough and fatigue showing positivity of 2-deoxy-2-[18F]fluoro-D-glucose positron-emission tomography/computed tomography total body imaging which turned out to normal after six and eighteen months of prednisone and pirfernidone treatment. Keywords: Positron-emission tomography/computed tomography (PET/CT), Idiopathic mediastinal fibrosis

Introduction: The conventional evaluation of neural telemetry and impedance requires the use of the computer coupled to an interface, with software that provides visualization of the stimulus and response. Recently, a remote control (CR220®) was launched in the market, that allows the performance of intraoperative tests with minimal instrumentation. Objective: To evaluate the agreement of the impedance values and neural telemetry thresholds, and the time of performance in the conventional procedure and by the remote control. Methods: Multicentric prospective cross-sectional study. Intraoperative evaluations of cochlear implants compatible with the use of CR220® were included. The tests were carried out in the 22 electrodes to compare the time of performance in the two situations. The agreement of the neural telemetry threshold values obtained from five electrodes was analyzed, and the agreement of impedance was evaluated by the number of electrodes with altered values in each procedure. Results: There were no significant difference between the impedance values. There was a moderate to strong correlation between the electrically-evoked compound action potential thresholds. The mean time to perform the procedures using the CR220 was significantly lower than that with the conventional procedure. Conclusion: The use of the CR220 provided successful records for impedance telemetry and automatic neural response telemetry. Resumo: Introdução: A avaliação convencional da telemetria neural e de impedâncias implica o uso do computador acoplado a uma interface, o software fornece o estímulo e a visualização das respostas. Recentemente, foi lançado um controle remoto (CR220®), que possibilita testes intraoperatórios com instrumental mínimo. Objetivo: Avaliar a concordância dos valores das impedâncias e dos limiares da telemetria neural e o tempo de execução no procedimento convencional e pelo controle remoto. Método: Estudo prospectivo transversal multicêntrico. Foram incluídas as avaliações intraoperatórias de implante coclear compatível com o uso do CR220®. Os testes foram realizados nos 22 eletrodos para comparar os tempos de execução nas duas situações. Foi analisada a concordância dos valores do limiar da telemetria neural obtidos em cinco eletrodos e a concordância das impedâncias foi avaliada pelo número de eletrodos com valores alterados em cada procedimento. Resultados: Não houve diferença significante entre as impedâncias. Obteve-se moderada a forte correlação entre os limiares do potencial de ação composto eletricamente evocado. O tempo médio para os procedimentos com o CR220 foi significativamente menor do que com o procedimento convencional. Conclusão: O uso do CR220 proporcionou registros bem-sucedidos para a telemetria de impedância e a telemetria automática de respostas neurais. Keywords: Cochlear implant, Impedance, Evoked potential, Telemetry, Palavras-chave: Implante coclear, Impedâncias, Potencial evocado, Telemetria

Stable water isotopes are widely used in ecohydrology to trace the transport, storage, and mixing of water on its journey through landscapes and ecosystems. Evaporation leaves a characteristic signature on the isotopic composition of the water that is left behind, such that in dual-isotope space, evaporated waters plot below the local meteoric water line (LMWL) that characterizes precipitation. Soil and xylem water samples can often plot below the LMWL as well, suggesting that they have also been influenced by evaporation. These soil and xylem water samples frequently plot along linear trends in dual-isotope space. These trend lines are often termed "evaporation lines" and their intersection with the LMWL is often interpreted as the isotopic composition of the precipitation source water. Here we use numerical experiments based on established isotope fractionation theory to show that these trend lines are often by-products of the seasonality in evaporative fractionation and in the isotopic composition of precipitation. Thus, they are often not true evaporation lines, and, if interpreted as such, can yield highly biased estimates of the isotopic composition of the source water., Hydrology and Earth System Sciences, 22 (5), ISSN:1027-5606, ISSN:1607-7938

Agricultural terraces are widely spread all over the world and are among the most evident landscape signatures of the human fingerprint, in many cases dating back to several centuries. Agricultural terraces create complex anthropogenic landscapes traditionally built to obtain land for cultivation in steep terrains, typically prone to runoff production and soil erosion, and thus hardly suitable for rain-fed farming practices. In addition to acquiring new land for cultivation, terracing can provide a wide array of ecosystem services, including runoff reduction, water conservation, erosion control, soil conservation and increase of soil quality, carbon sequestration, enhancement of biodiversity, enhancement of soil fertility and land productivity, increase of crop yield and food security, development of aesthetic landscapes and recreational options. Moreover, some terraced areas in the world can be considered as a cultural and historical heritage that increases the asset of the local landscape. Terraced slopes may be prone to failure and degradation issues, such as localized erosion, wall or riser collapse, piping, and landsliding, mainly related to runoff concentration processes. Degradation phenomena, which are exacerbated by progressive land abandonment, reduce the efficiency of benefits provided by terraces. Therefore, understanding the physical processes occurring in terraced slopes is essential to find the most effective maintenance criteria necessary to accurately and adequately preserve agricultural terraces worldwide.

The time that water takes to travel through the terrestrial hydrological cycle and the critical zone is of great interest in Earth system sciences with broad implications for water quality and quantity. Most water age studies to date have focused on individual compartments (or subdisciplines) of the hydrological cycle such as the unsaturated or saturated zone, vegetation, atmosphere, or rivers. However, recent studies have shown that processes at the interfaces between the hydrological compartments (e.g., soil-atmosphere or soil-groundwater) govern the age distribution of the water fluxes between these compartments and thus can greatly affect water travel times. The broad variation from complete to nearly absent mixing of water at these interfaces affects the water ages in the compartments. This is especially the case for the highly heterogeneous critical zone between the top of the vegetation and the bottom of the groundwater storage. Here, we review a wide variety of studies about water ages in the critical zone and provide (1) an overview of new prospects and challenges in the use of hydrological tracers to study water ages, (2) a discussion of the limiting assumptions linked to our lack of process understanding and methodological transfer of water age estimations to individual disciplines or compartments, and (3) a vision for how to improve future interdisciplinary efforts to better understand the feedbacks between the atmosphere, vegetation, soil, groundwater, and surface water that control water ages in the critical zone. © 2019. The Authors., This review is based on discussions at the workshop on Water Ages in the Hydrological Cycle, held in the Black Forest in October 2017 and funded by the Wassernetzwerk Baden-W?rttemberg. We thank the attendees of the workshop R. B?umle, T. Gebauer, D. Gooddy, P. K?niger, M. Loschko, V. Maurer, R. Purtschert, S. Seeger, and H. Wang. M. S. thanks Wassernetzwerk Baden-W?rttemberg and the Deutsche Forschungsgemeinschaft (DFG)?Project 397306994?for funding. N. R. thanks the Luxembourg National Research Fund (C14/SR/8353440/STORE-AGE) for financial support. A. H. was supported by the Emmy Noether Programme of the Deutsche Forschungsgemeinschaft DFG (HA 8113/1-1). This research manuscript by Matthias Sprenger was supported by the Ministerium f?r Wissenschaft, Forschung und Kunst Baden-W?rttemberg (Az. 33-7533.-25-11/31).

Hillslope-stream connectivity significantly affects streamflow and water quality responses during rainfall and snowmelt events, but is difficult to quantify. One approach to quantify subsurface hillslope-stream connectivity is graph theory, which considers linear connections between groundwater measurement sites. We quantified subsurface connectivity based on surface topography and shallow groundwater data from four small (

Il rilievo dell’umidità degli strati più superficiali del suolo alla scala di campo, ossia in pixel di dimensioni nell’ordine degli ettari, è sempre più diffuso grazie alla disponibilità di sensori di ultima generazione. Tuttavia, le applicazioni di modelli di bilancio idrico del suolo richiedono la conoscenza della distribuzione dell’umidità del suolo riferite alla scala locale, ossia quella di un pixel di dimensioni nell’ordine di pochi metri quadrati. Questo studio esamina la possibilità di trasferire le informazioni sull’umidità del suolo dalla scala di campo alla scala locale con un approccio che associa un modello idrologico “a serbatoio” a di una tecnica fisicamente basta per il passaggio di scala. Il metodo proposto è meno impegnativo rispetto ai rilievi diretti poiché richiede solo la conoscenza di dati climatici (input del modello “a serbatoio”) e di dati topografici (input per il passaggio di scala spaziale). Per la fase di calibrazione sono state utilizzate misure di umidità del suolo in superficie eseguite con sonde TDR (Time Domain Reflectrometry). Il metodo messo a punto in questo studio è stato implementato in tre siti sperimentali italiani, caratterizzati da condizioni differenti sia climatiche sia topografiche. I confronti offrono interessanti spunti interpretativi poiché in questi siti le variazioni di umidità del suolo dipendono da indici topografici legati all’afflusso di acqua verso valle (sito nell’Italia settentrionale) oppure sono legati alle dinamiche idrologiche di versante dominate da processi evapotraspirativi (sito nell’Italia meridionale). Molto interessante è il caso del sito dell’Italia centrale in cui si riscontra una alternanza dei processi idrologici dominanti legati al deflusso laterale durante la stagione umida e alla radiazione solare durante la stagione secca. Tenendo conto di futuri cambiamenti climatici, l’instabilità temporale dei modelli di umidità del suolo rilevati in quest’ultimo sito può essere correlata all’indice di aridità stagionale.

In this study we investigate the surface flow time of rise in response to rainfall and snowmelt events at different spatial scales and the main sources originating channel runoff and spring water in a steep nested headwater catchment (Rio Vauz, Italian Dolomites), characterized by a marked elevation gradient. We monitored precipitation at different elevations and measured water stage/streamflow at the outlet of two rocky subcatchments of the same size, representative of the upper part of the catchment dominated by outcropping bedrock, at the outlet of a soil-mantled and vegetated subcatchment of similar size but different morphology, and by the outlet of the main catchment. Hydrometric data are coupled with stable isotopes and electrical conductivity sampled from different water sources during five years, and used as tracers in end-member mixing analysis, application of the two component mixing model and analysis of the slope of the dual-isotope regression line. Results reveal that times of rise are slightly shorter for the two rocky subcatchments, particularly for snowmelt and mixed rainfall/snowmelt events, compared to the soil-mantled catchment and the entire Rio Vauz catchment. The highly-variable tracer signature of the different water sources reflects the geomorphological and geological complexity of the study area. The principal end-members for channel runoff and spring water are identified in rainfall and snowmelt, which are the dominant water sources in the rocky upper part of the study catchment, and soil water and shallow groundwater, which play a relevant role in originating baseflow and spring water in the soil-mantled and vegetated lower part of the catchment. Particularly, snowmelt contributes up to 64% ± 8% to spring water in the concave upper parts of the catchment and up to 62% ± 11% to channel runoff in the lower part of the catchment. These results offer new experimental evidences on how Dolomitic catchments capture and store rain water and meltwater, releasing it through a complex network of surface and subsurface flow pathways, and allow for the construction of a preliminary conceptual model on water transmission in snowmelt-dominated catchments featuring marked elevation gradients

Understanding water sources for crop water uptake in agricultural and agroforestry systems is an essential step to develop more efficient and sustainable water management strategies, which is increasingly important in the light of current world population growth, changing climatic conditions and consequent growing pressures on agricultural- and agroforestry production. Stable isotopes of hydrogen and oxygen in the water molecule are powerful and, nowadays, affordable tracers that can help to define the proportion of water sources accessed by plants. Yet, contrary to natural environments, their application is still relatively limited in agricultural and agroforestry research. In this work, we synthesize the advantages and the current knowledge deriving from the use of the stable isotopes of hydrogen and oxygen, in support of more traditional techniques, to understand root water uptake dynamics in agricultural and agroforestry systems. We also underline the practical implications related to the application of this technique for management purposes, and provide a vision for new challenges and future research opportunities in exploring crop and plant water use based on isotopic data.

Suspended and bedload transport in mountain rivers are notoriously difficult to monitor and thus to quantify. Even more challenging are proglacial streams that are generally characterized by high flow velocities, high sediment concentrations and transport rates, large and abrupt temporal variability of water discharge and transport rates, as well as by frequent morphological changes. However, the quantification of suspended and bedload transport rates is crucial to understand and predict short- and long-term morphodynamics in such sensitive systems. In this chapter, we present an updated summary on the current knowledge on the monitoring methods and on the observed dynamics of sediment transport in proglacial rivers, including both suspended and bedload fractions.

This work evaluates the predictive power of the quasi-dynamic shallow landslide model QD-SLaM to simulate shallow landslide locations in a small-scale Mediterranean landscape, namely, the lower portion (2.6 km2) of the Giampilieri catchment, located in Sicily (Italy). The catchment was impacted by a sequence of high-intensity storms over the years 2007–2009, resulting in widespread landsliding, with a total landslide initiation area amounting to 2.6% of the basin area. The effect of high-resolution digital terrain models (DTMs) on the quality of model predictions is tested by considering four DTM resolutions: 2, 4, 10 and 20 m. Moreover, the impact of the dense forest road network on the model performance is evaluated by separately considering road-related landslides and natural landslides. The landslide model does not incorporate the description of road-related failures and is applied without calibration of the model parameters. The model predictive power is shown to be DTM-resolution dependent. Use of coarser resolution has a smoothing effect on terrain attributes, with local slope angles decreasing and contributing areas becoming larger. The percentage of watershed area represented by the model as unconditionally unstable (i.e. failing even without the addition of water from precipitation) ranges between 6.3% at 20 m DTM and 13.8% at 2 m DTM, showing an overestimation of the mapped landslide area. We consider this prediction as an indication for likely failing sites in future storms rather than areas proved stable during previous storms. When assessed over the sample of mapped non-road-related landslides, better model performances are reported for 4 and 10 m DTM resolution, thus highlighting the fact that higher DTM resolution does not necessarily mean better model performances. Model performances over road-related failures are lower than for the natural cases, and slightly increase with decreasing DTM resolution. These findings indicate that to realize the full potential of high-resolution topography, more extensive work is needed aiming more specifically to identify the extent of the artificial structures and their impact on shallow landsliding processes., Hydrology and Earth System Sciences, 18 (6), ISSN:1027-5606, ISSN:1607-7938

In this commentary, we build on discussions that emerged during the workshop "Isotope-based studies of water partitioning and plant-soil interactions in forested and agricultural environments" held in San Casciano Val di Pesa, Italy, in September 2017. Quantifying and understanding how water cycles through the Earth's critical zone is important to provide society and policy makers with the scientific background to manage water resources sustainably, especially considering the ever-increasing worldwide concern about water scarcity. Stable isotopes of hydrogen and oxygen in water have proven to be a powerful tool to track water fluxes in the critical zone. However, both mechanistic complexities (e.g., mixing and fractionation processes, heterogeneity of natural systems) and practical methodological issues (e.g., lack of standard protocols to sample specific compartments, such as soil water and xylem water) limit the application of stable water isotopes in critical zone science. In this commentary, we examine some of the opportunities and critical challenges of using isotope-based ecohydrological applications, and outline new perspectives focused on interdisciplinary research opportunities for this important tool in water and environmental science.

The understanding of the hydrological and hydrochemical functioning of glacierized catchments require the knowledge of the different controlling factors and their mutual interplay. For this purpose, the present study was carried out in two sub-catchments of the Sulden River catchment (130 km2, Eastern Italian Alps) in 2014 and 2015, characterized by similar size but contrasting geological setting. Samples were taken at different space and time scales for analysis of stable isotopes of water, electrical conductivity, major, minor and trace elements. At the monthly sampling scale for different spatial scales (0.05–130 km2), complex spatial and temporal dynamics such as contrasting EC gradients in both sub-catchments were found. At the daily scale, for the entire Sulden catchment the relationship between discharge and electrical conductivity showed a monthly hysteretic pattern. Hydrometric and geochemical dynamics were controlled by an interplay of meteorological conditions and geological heterogeneity. After conducting a PCA analysis, the largest share of variance (36.3 %) was explained by heavy metal concentrations (such as Al, V, Cr, Ni, Zn, Cd, Pb) during the melting period while the remaining variance (16.3 %) resulted from the bedrock type in the upper Sulden sub-catchment (inferred from EC, Ca, K, As and Sr concentrations). Thus, high concentrations of As and Sr in rock glacier outflow may more likely result from bedrock weathering. Furthermore, nivo-meteorological indicators such as maximum daily global solar radiation, three day maximum air temperature, and 15 day snow depth differences could explain the monthly conductivity and isotopic dynamics best. The decrease of snow depth calculated for different time lengths prior to the sampling day showed best agreements with conductivity and isotopic dynamics when time lengths varied. These insights may help to better predict hydrochemical catchment responses linked to meteorological and geological controls and to guide future classifications of glacierized catchments according to their hydrochemical characteristics.

Erdheim-Chester Disease (ECD) is a rare non Langerhans cell histiocytosis of unknown origin with multiorgan involvement. We report a case of a man who presented to us with haematuria, asthenia, fever, nausea and malleolar oedema. After computed tomography and magnetic resonance imaging, the patient underwent a Positron Emission Tomography/Computed Tomography (PET/CT) with 18F-fluorodeoxyglucose (18F-FDG) that revealed multiple focal uptake in the skeleton and also visceral and vascular involvement. After a retroperitoneal biopsy, diagnosis of ECD was made. The treatment begun with steroids and after one month, a second 18F-FDG PET/CT was performed, highlighting a partial response. After five months of specific treatment with inhibitors of tyrosine kinases, a third 18F-FDG PET/CT was done showing a complete response. The 18F-FDG PET/CT allows assessing the extent of involvement in ECD, to detect the most easily accessible sites for diagnostic biopsy and to monitor disease activity and response to consolidated and new therapies.