Brief communication: Mountain permafrost acts as an aquitard during an infiltration experiment monitored with electrical resistivity tomography time-lapse measurements

Frozen layers within the subsurface of rock glaciers are generally assumed to act as aquicludes or aquitards. So far, this behavior has been mainly defined by analyzing the geochemical characteristics of spring waters. In this work, for the first time, we experimentally confirmed this assumption by executing an infiltration test in a rock glacier of the Southern Alps, Italy. Time-lapse electrical resistivity tomography (ERT) technique monitored the infiltration of 800 L of saltwater released on the surface of the rock glacier; 24 h ERT monitoring highlighted that the injected water was not able to infiltrate into the underlying frozen layer.</p

Comparing hydrological responses across catchments using a new soil water content metric

Soil water content (SWC) is a fundamental variable involved in several hydrological processes governing catchment functioning. Comparative analysis of hydrological processes in different catchments based on SWC data is therefore beneficial to infer driving factors of catchment response. Here, we explored the use of high-temporal resolution SWC data in three forested catchments (2.4–60 ha) in different European climates to characterize hydrological responses during wet and dry conditions. The investigated systems include Ressi, Italy, with a humid temperate climate, Weierbach, Luxembourg, with a semi-oceanic climate, and Can Vila, Spain, with a Mediterranean climate. We introduced a new SWC metric defined as the difference between seasonal mean SWC at a relatively shallow and a deep soil layer. The difference is classified in three distinct states: similar SWC between the two layers, higher SWC in the deeper layer, and higher SWC in the shallow layer. In the most humid site, Ressi, we frequently found similar SWC at the two soil depths which was associated with high runoff ratios. Despite similar precipitation amounts in Can Vila and Weierbach, SWC patterns were very different in both catchments. In Weierbach, SWC was similar across the entire soil profile during wet conditions, whereas evaporation of shallow water resulted in higher SWC in the deep soil layer during dry conditions. This led to high runoff ratios during wet conditions and low runoff ratios during dry conditions. In Can Vila, SWC was consistently higher in the deeper layer compared to the shallow layer, irrespective of the season, suggesting an important role of hydraulic redistribution and vertical water movement in this site. Our approach provides an easy and useful method to assess differences in hydrological behaviour solely based on SWC data. As similar datasets are increasingly collected and available, this opens the possibility for further analyses and comparisons in sites around the globe with contrasted physiographic and climate characteristics.C. Segura acknowledges a Fulbright Fellowship that supported her stay at the University of Florence, Italy and the National Science Foundation Award No. 1943574. The Weierbach datasets have been collected in the framework of the Doctoral Training Unit HYDRO-CSI (Innovative methodologies for unravelling hydrological, chemical, and biological interactions across multiple scales), funded by the National Research Fund of Luxembourg (grant PRIDE15/10623093). Data collection in Ressi catchment was supported by the projects “Ecohydrological Dynamics and Water Pathways in Forested Catchments” (Bando Starting Grants 2015, Fondazione Cassa di Risparmio di Padova e Rovigo), the project “SILVA-Water fluxes between soil, vegetation and atmosphere: a comparative analysis in two Italian forested catchments” (funded by Premio Florisa Melone 2018, assigned by the Italian Hydrological Society), the Italian MIUR Project (PRIN 2017) “WATer mixing in the critical ZONe: observations and predictions under environmental changes-WATZON” (code: 2017SL7ABC), and the RETURN Extended Partnership, receiving funding from the European Union Next-GenerationEU (National Recovery and Resilience Plan – NRRP, Mission 4, Component 2, Investment 1.3 – D.D. 1243 2/8/2022, PE0000005). J. Latron and L. Pfister contributions have been supported by the RHYSOTTO (PID2019-106583RB-I00) and WARMed (PID2022-141868NB-I00) projects, both funded by the Spanish Ministry of Science and Innovation (Ministerio de Ciencia e Inovación, Agencia Estatal de Investigación). J. Latron and L. Pfister also acknowledge the collaboration of Gisel Bertran and Elisenda Sánchez during field work and data collection. The results of this study were discussed within the COST Action: “WATSON” CA19120. We also thank the constructive reviews from Nitin Singh and an anonymous reviewer.Peer reviewe

Ideas and perspectives : Tracing terrestrial ecosystem water fluxes using hydrogen and oxygen stable isotopes – challenges and opportunities from an interdisciplinary perspective

The authors thank Marialaura Bancheri, Michele Bottazzi, Roman Cibulka, Massimo Esposito, Alba Gallo, Cesar D. Jimenez-Rodriguez, Angelika Kuebert, Ruth Magh, Stefania Mambelli, Alessia Nannoni, Paolo Nasta, Vladimir Rosko, Andrea Rücker, Noelia Saavedra Berlanga, Martin Šanda, and Anna Scaini for their contributions during the discussion at the workshop “Isotope-based studies of water partitioning and plant–soil interactions in forested and agricultural environments”. The authors also thank “Villa Montepaldi” and the University of Florence for the access to the workshop location, and the municipality of San Casciano in Val di Pesa for logistical support. The authors thank the Department of Innovation, Research and University of the Autonomous Province of Bozen/Bolzano for covering the Open Access publication costs. Last, but not least, the authors wish to thank Matthias Sprenger, Stephen Good, and J. Renée Brooks, as well as the Editor David R. Bowling, whose constructive reviews greatly improved this manuscript.Peer reviewedPublisher PD

Runoff generation in mountain catchments: long-term hydrological monitoring in the Rio Vauz Catchment, Italy

Trying to obtain a more detailed understanding of the hydrological functioning of mountain catchments represents an important challenge in the effort of counteracting possible consequences of climate and land use change on water resources availability. Long-term (> 10 years) hydro-meteorological monitoring in small (typically 10 años) en pequeñas (< 10 km2) cuencas experimentales constituye una herramienta muy valiosa para conseguir este objetivo. La cuenca del Río Vauz (1,9 km2) en los Dolomitas italianos, representa un ejemplo excelente de cuenca monitorizada a largo plazo, afectada por proceso de fusión de nieve en regiones dolomíticas. El fuerte gradiente altitudinal de la cuenca del Río Vauz y las diferentes propiedades fisiográficas de sus cuencas anidadas hace que éste sea un sitio único para investigar los mecanismos fundamentales de generación de escorrentía en cuencas de cabecera en zonas de montaña. En este trabajo se ofrece una revisión de los procesos físicos que se infieren a partir del seguimiento hidrológico que se ha llevado a cabo en esta cuenca a lo largo de 12 años. Se presenta la base de datos disponible y se sintetizan los procesos hidrológicos principales que explican el funcionamiento interno de la cuenca del Río Vauz, centrándose en los siguientes comportamientos hidrológicos: umbrales, histéresis y conectividad. El principal mecanismo que controla el umbral de respuesta de las escorrentías superficial y subsuperficial está constituido por la combinación de tres factores: condiciones antecedentes de la humedad del suelo, volumen de precipitación y topografía. Los cambios en los patrones de las curvas de histéresis (horarias y anti-horarias) entre caudal, humedad del suelo, nivel freático y conductividad eléctrica están determinados por la ocurrencia de procesos de generación de escorrentía diferentes y las características del evento de precipitación. La conectividad ladera-ribera-cauce está controlada por las condiciones antecedentes de humedad y el volumen de precipitación. La composición de los trazadores ambientales (isótopos estables del agua y conductividad eléctrica) en distintas fuentes de agua y la aplicación de modelos mixtos basados en trazadores ayudan a diferenciar las fuentes de escorrentía y cuantificar el papel de la lluvia y la fusión de nieve en el caudal. Finalmente, se define un modelo perceptual de procesos de generación de escorrentía en condiciones secas y húmedas que puede ser considerado representativo de muchas cuencas de cabecera en zonas de montaña del mundo

Runoff generation in mountain catchments: long-term hydrological monitoring in the Rio Vauz Catchment, Italy

Trying to obtain a more detailed understanding of the hydrological functioning of mountain catchments represents an important challenge in the effort of counteracting possible consequences of climate and land use change on water resources availability. Long-term (> 10 years) hydro-meteorological monitoring in small (typically 10 años) en pequeñas (< 10 km2) cuencas experimentales constituye una herramienta muy valiosa para conseguir este objetivo. La cuenca del Río Vauz (1,9 km2) en los Dolomitas italianos, representa un ejemplo excelente de cuenca monitorizada a largo plazo, afectada por proceso de fusión de nieve en regiones dolomíticas. El fuerte gradiente altitudinal de la cuenca del Río Vauz y las diferentes propiedades fisiográficas de sus cuencas anidadas hace que éste sea un sitio único para investigar los mecanismos fundamentales de generación de escorrentía en cuencas de cabecera en zonas de montaña. En este trabajo se ofrece una revisión de los procesos físicos que se infieren a partir del seguimiento hidrológico que se ha llevado a cabo en esta cuenca a lo largo de 12 años. Se presenta la base de datos disponible y se sintetizan los procesos hidrológicos principales que explican el funcionamiento interno de la cuenca del Río Vauz, centrándose en los siguientes comportamientos hidrológicos: umbrales, histéresis y conectividad. El principal mecanismo que controla el umbral de respuesta de las escorrentías superficial y subsuperficial está constituido por la combinación de tres factores: condiciones antecedentes de la humedad del suelo, volumen de precipitación y topografía. Los cambios en los patrones de las curvas de histéresis (horarias y anti-horarias) entre caudal, humedad del suelo, nivel freático y conductividad eléctrica están determinados por la ocurrencia de procesos de generación de escorrentía diferentes y las características del evento de precipitación. La conectividad ladera-ribera-cauce está controlada por las condiciones antecedentes de humedad y el volumen de precipitación. La composición de los trazadores ambientales (isótopos estables del agua y conductividad eléctrica) en distintas fuentes de agua y la aplicación de modelos mixtos basados en trazadores ayudan a diferenciar las fuentes de escorrentía y cuantificar el papel de la lluvia y la fusión de nieve en el caudal. Finalmente, se define un modelo perceptual de procesos de generación de escorrentía en condiciones secas y húmedas que puede ser considerado representativo de muchas cuencas de cabecera en zonas de montaña del mundo

Alternative methods to determine the δ2H-δ18O relationship: An application to different water types

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)