1,720,979 research outputs found
Electromagnetic and self-potential investigation to detect seepage of irrigation canals
No full textWe adopted electromagnetic induction (EMI) and self-potential measurements along irrigation canal bank in order to detect groundwater seepage. The EMI methods is sensitive to the electrical conductivity of the subsoil, that is affected by the salt and clay content and water content. The depth of investigation depends on the soil electrical conductivity, the geometry of the instrument and the frequency of the electromagnetic field. The experimental data refers to anintegrated survey along a transect on an irrigation canals (400 m) .We acquired broadband electromagnetic data using a Profiler EMP400 (GSSI), with coil separation of 1.22 m and a bandwidth ranging from 1 to 15 kHz. The self-potential measurements were performed with a fixed electrode and a moving electrode along the same transect of EMI measurements. The interval spacing among self-potential measurements was 2 m. Visual inspection of the canal permitted to compare the evidence of seepage losses with the geophysical anomalies. The results of self-potential measurements show peaks of electrical potential at the same position of electrical conductivity anomalies. Integration of the EMI survey and SP measurements is useful to detect seepage losses from canals: a more detailed analysis of self potential anomalies is required to reduce "false" alarms
Monitoring Ecohydrological Variables in a Peri-Urban Forest and a Non-glacial High-Elevation Grassland Representing Possible Future Conditions in the Alps
No full textMountain environments often suffer from a scarcity of comprehensive environmental data that are the starting point for a better understanding of ecohydrological dynamics and for the validation, or improved conceptualization, of hydrological and land surface models. Recognizing the critical importance of understanding these environments to address the challenges of water resource management under unsettling future climate scenarios, research efforts are underway to address the lack of information. This study focuses on the comprehensive monitoring of ecohydrological variables within two contrasting catchments in Northwestern Italy. The first catchment (Colle del Nivolet, Aosta Valley) is monitored with a station located in a non-glacial high-elevation (2555 m a.s.l.) grassland. The second catchment (Bussoleno Grangia dell’Alpe) is monitored through a station at 650 m a.s.l. in a peri-urban forest. The research employs advanced monitoring techniques such as cosmic ray probes, environmental tracers (such as stable water isotopes in vegetation, soil and streamwater), and the eddy-covariance setup for atmospheric monitoring. In this regard, micrometeorological instruments have been installed on a 5 m-high mast (grassland site) and a 25 m-high mast (forest site). The previously mentioned monitoring techniques lead to the investigation of key ecohydrological variables such as energy, water vapor and carbon dioxide fluxes, 3D wind speed, soil moisture, soil matric potential, 4-component solar radiation, snow water equivalent, and the water isotope content whose integration provides necessary insights of hydrological and ecohydrological processes occurring from the plot to the catchment scale. Continuous monitoring over several years covering a wide range of wetness conditions, including the (probably) worst drought in the past two centuries in Northern Italy, lays the foundations for the identification of trends, anomalies, and potential shifts in these variables, thus providing a picture of the ecosystems' adaptive capacities in the face of evolving environmental conditions
Space-time soil moisture variability for two different land use types: analysis at the plot scale
No full textTrends of some high quantiles of average and extremes inter-arrival times and rainfall depths at daily scale for an Italian Sub-Alpine area.
Full text linkModeling of rainfall statistical structure represents an important research area in hydrology, meteorology,
atmospheric physics and climatology, because of the several theoretical and practical implications. The statistical
inference of the alternation of wet periods (WP) and dry periods (DP) in daily rainfall records can be achieved
through the modelling of inter-arrival time-series (IT), defined as the succession of times elapsed from a rainy day
and the one immediately preceding it. It has been shown previously that the statistical structure of IT can be well described by the 3-parameter
Lerch distribution (Lch). In this work, Lch was successfully applied to IT data belonging to a sub-alpine
area (Piemonte and Valle d’Aosta, NW Italy); furthermore the same statistical procedure was applied to daily
rainfall records to ITs associated. The analysis has been carried out for 26 daily rainfall long-series ( 90 yr of
observations). The main objective of this work was to detect temporal trends of some features describing the statistical
structure of both inter-arrival time-series (IT) and associated rainfall depth (H). Each time-series was divided on
subsets of five years long and for each of them the estimation of the Lch parameter was performed, so to extend
the trend analysis to some high quantiles
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Long-Range Low-Power Soil Water Content Monitoring System for Precision Agriculture
Full text linkWorld population growth and desertification are increasing the food demand. Food production must increase to ensure food security in the following years. Smart agriculture tries to improve food production thanks to the adoption of electronic sensors to monitor and control fruit and vegetable crops. Another critical point in agriculture is the use of potable water. Precision irrigation strategies can be implemented to reduce water waste and increase crop production. This paper proposes a long-range, low-power sensor node to monitor soil water content. It is possible to place multiple sensor nodes in the field and use the gathered data to determine the most suitable irrigation strategy. The node communicates thanks to the LoRa protocol and it can also be used in remote areas where it is impossible to have an internet connection
Towards a conceptualization of the hydrological processes behind changes of young water fraction with elevation: A focus on mountainous alpine catchments
Full text linkThe young water fraction (F-yw*), defined as the fraction of catchment outflow with transit times of less than 2-3 months, is increasingly used in hydrological studies that exploit the potential of isotope tracers. The use of this new metric in catchment intercomparison studies is helpful to understand and conceptualize the relevant processes controlling catchment functioning. Previous studies have shown surprising evidence that mountainous catchments worldwide yield low F-yw*. These low values have been partially explained by isolated hydrological processes, including deep vertical infiltration and long groundwater flow paths. However, a thorough framework illustrating the relevant mechanisms leading to a low F-yw* in mountainous catchments is missing.The main aim of this paper is to give an overview of what drives F-yw* variations according to elevation, thus clarifying why it generally decreases at high elevation. For this purpose, we assembled a data set of 27 study catchments, located in both Switzerland and Italy, for which we calculate F-yw*. We assume that this decrease can be explained by the groundwater storage potential, quantified by the areal extent of Quaternary deposits over a catchment (F-qd), and the low-flow duration (LFD) throughout the period of isotope sampling (PoS). In snow-dominated systems, LFD is strictly related to the snowpack persistence, quantified through the mean fractional snow cover area (F-SCA). The drivers are related to the catchment storage contribution to the stream that we quantify by applying a cutting-edge baseflow separation method to the discharge time series of the study sites and by estimating the mean baseflow fraction (F-bf) over the PoS.Our results suggest that Quaternary deposits could play a role in modulating F-yw* elevation gradients via their capacity to store groundwater, but subsequent confirmation with further, more detailed geological information is necessary. LFD indicates the proportion of PoS in which the stream is sustained and dominated by stored water coming from the catchment storage. Accordingly, our results reveal that the increase of LFD at high elevations, to a large extent driven by the persistence of winter snowpacks and the simultaneous lack of a liquid water input to the catchments, results in lower F-yw*. In our data set, F-bf reveals a strong complementarity with F-yw*, suggesting that the latter could be estimated as F-yw*-1-F-bf for catchments without stable water isotope measurements.As a conclusion, we develop a perceptual model that integrates all the results of our analysis into a framework for how hydrological processes control F-yw* according to elevation. This lays the foundations for an improvement of the theory-driven models
Toward improved understanding of land use effect on soil moisture variability: analysis and modelling at the plot scale
No full textVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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