Matteo Censini

<p>This study presents a methodology to assess the spatiotemporal dynamics of water movement at the hillslope scale using geophysical techniques in order to identify preferential flow paths, estimate hydraulic conductivity, and ultimately understand runoff generation processes and predict streamflow response in small catchments. </p> <p>The study area is a 0.3 km2 forested headwater catchment in the Tuscan Apennines, central Italy. We used ground penetrating radar (GPR) and time-lapse electrical resistivity profiles (ERT) to respectively infer the soil bedrock depth and measure the movement of water through the subsurface and track its transit time along the hillslope. We applied these techniques during repeated infiltration experiments conducted over a 1m2 plot where more than 1m3 of water was applied in approximately 24 hours.</p> <p>We constructed a hydrological model simulating the observed infiltration events using multiple soil layers that corresponded with variations in bedrock depth, as revealed by the GPR data. The next step involves calibrating the hydrological parameters through a hydrogeophysical inversion framework, where the simulated resistivities will be compared with the measured ones.  The model will then be applied over an extended period under natural atmospheric demands conditions, to the prediction of groundwater residence, and the conditions under which plants can access it.</p>

In this study we aimed to use the technique of geoeletrical prospection ERT, to investigate the interaction between the soil and the root system of an Olive tree sited in Tuscany. The data have been elaborated through various softwares like Prosys II, Paraview and MatLab. The results obtained show how this approach can give us information related to the location of the roots in the soil, and trace the diffusion of the wet volume in a time-lapse sequence

Subsurface flow at the hillslope scale is a critical process responsible for water redistribution and transport of nutrients to the stream. Despite its hydrological importance, understanding the mechanisms governing subsurface flow generation is still challenging.  We investigated the case of a small forested catchment located in the Apennine mountains, Tuscany, central Italy, which experiences shallow lateral downslope water redistribution resulting in substantial differences in vadose zone water supply along the hillslope. We developed an integrated experimental and modelling approach in order to shed some light on the role of the subsurface structure on the generation of hillslope-scale subsurface flow in the study catchment.   We used a combination of methods sensitive to different soil properties. Ground Penetrating Radar (GPR) surveys show a complex response reflecting the interplay of different factors such as the presence of rocks, banks and counterslope in the near-surface and thus highlighting the very heterogeneous soil that may control water flow patterns. Several Electromagnetic (EM) mappings were conducted and show top-down hillslope variations of soil electrical conductivity revealing that trees located at the footslope and that experience longer vegetative periods might benefit from larger soil moisture content compared to the smaller trees located on the hillslope top. Similar observations are made from the two parallel top-bottom hillslope Electrical Resistivity Tomography (ERT) transects.  The geophysical results will be integrated into hydrogeological simulations using the CATHY model for different scenarios (e.g., initial soil moisture, preferential flow paths, drainable porosity, soil properties, bedrock topography or stratification of soils) to explore the main drivers for subsurface preferential flow. 

<p>In forested catchments, stemflow affects the amount of precipitation reaching the soil, how water infiltrates and transports nutrients into the soil. Recently, the ecohydrological community has shown a renewed interest towards the methods used to quantify the stemflow infiltration area. Stemflow infiltration area is generally estimated based on the ratio between stemflow input rate and the mean soil infiltration capacity, whereas direct observations are rare. Direct estimations of stemflow infiltration areas are usually made by the application of dye tracers, which have proven to be useful for monitoring double-funneling. On the contrary, there are still few observations based on the application of electrical resistivity tomography (ERT) and isotopically-labelled water.</p><p>In this study, we present a simple experiment carried out for a beech tree, in a forested hillslope in the Italian pre-Alps. The aims of the experiment were to simulate stemflow by using salt and isotopically-labelled water, and to quantify stemflow infiltration area and volume.</p><p>The experiment was performed during a dry period in September 2022, in order to observe marked changes in the isotopic signature of soil water, as well as in electrical resistivity. Stemflow was simulated with a rainfall depth and intensity similar to typical summer storms in the catchment, and by using salt water with an isotopic composition very different compared to the composition of soil water during summer months. Before, during and after the stemflow application, 9 ERT surveys were performed to capture the infiltration dynamics. The collection of soil samples for isotopic analysis was carried out after the experiment, at different distances from the stem and at different depths (e.g., 0-15, 15-30, and 30-45 cm). Soil moisture was also measured at 0-6 and 0-12 cm depths at different distances from the stem.</p><p>Preliminary results showed a rapid infiltration of stemflow along the root system of the beech tree, and 24 hours since the start of the experiment the labelled water had infiltrated up to 80 cm into the soil. This simple experiment showed the usefulness of using time lapse ERT surveys, as well as isotopically-labelled water to simulate stemflow and trace double-funneling.</p><p> </p><p> </p><p><em>Keywords:</em> stemflow, electrical resistivity tomography, stable water isotopes, soil water, forested catchment.</p>

Subsurface flow at the hillslope scale is a critical process responsible for water redistribution and transport of nutrients to the stream. Despite its hydrological importance, understanding the mechanisms governing subsurface flow generation is still challenging.  We investigated the case of a small forested catchment located in the Apennine mountains, Tuscany, central Italy, which experiences shallow lateral downslope water redistribution resulting in substantial differences in vadose zone water supply along the hillslope. We developed an integrated experimental and modelling approach in order to shed some light on the role of the subsurface structure on the generation of hillslope-scale subsurface flow in the study catchment.   We used a combination of methods sensitive to different soil properties. Ground Penetrating Radar (GPR) surveys show a complex response reflecting the interplay of different factors such as the presence of rocks, banks and counterslope in the near-surface ...

<p>Hydrological processes along mountain hillslopes involve complex interaction between soil storage and surface and subsurface flow, drainage and evapotranspiration. To capture this complexity, time-lapse extensive and intensive measurements are needed, potentially capable of providing spatially dense information in 3D and time frequent data. To this end, hydro-geophysical methods (ground penetration radar, GPR, electromagnetic induction, EMI and electrical resistivity tomography, ERT) based on electrical and electromagnetic laws are widely used as they naturally link to the electrical properties of soil moisture. ERT produces, especially in time lapse mode and using permanent installations, very detailed images of the water dynamics along hillslopes. While ERT requires galvanic contact with the ground, and thus relatively slow operations, EMI can be applied over large areas in a very short time. This method has been used for decades, mainly to produce apparent electrical conductivity (ECa) maps. Only recently, inversion of EMI data as a function of depth has become a viable practice.</p><p>In this work, we present two cases of hillslope monitoring using non-invasive methods, both performed as part of the WATZON project, funded by the Italian Ministry of University and Research (MIUR). The first case is the Mediterranean catchment of the Alento River, in southern Italy. The monitoring was carried out using 7 different EMI surveys, acquired in multifrequency mode (FDEM) between August 2020 and December 2021. The purpose of this survey was to characterize the structure of the basin’s subsoil within the first few meters, as well as to record the variation of electrical conductivity (EC) associated with seasonal variations. The second case is related to the Apennines catchment of the Re Della Pietra, located at the border between Tuscany and Emilia-Romagna in central Italy. The monitoring was carried out through 6 different EMI surveys, acquired in multifrequency mode (FDEM) between August 2020 and May 2021. The purpose of this survey was to characterize the structure of the basin’s subsoil within the first few meters, as well as to record the variation of electrical conductivity (EC) associated with seasonal variations. Furthermore, ERT measurements were carried out along a fixed line on the ground, according to the direction of the maximum slope. The combination of EMI and ERT proved particularly effective in delineating the hydrologic dynamics of the hillslope.</p>

In this study we aimed to use the technique of geoeletrical prospection ERT, to investigate the interaction between the soil and the root system of an Olive tree sited in Tuscany. The data have been elaborated through various softwares like Prosys II, Paraview and MatLab. The results obtained show how this approach can give us information related to the location of the roots in the soil, and trace the diffusion of the wet volume in a time-lapse sequence

<p>Advanced modeling of hydrological processes in mountain catchments requires accurate characterization of the shallow subsurface, and in particular the depth to the soil/bedrock interface. Frequency domain electromagnetic induction (EMI) methods are well suited to this challenge as they have short acquisition times and do not require direct coupling with the ground; consequently they can be highly productive. Moreover, although traditionally used for revealing lateral electrical conductivity changes, EMI inversion is increasingly used to quantitatively resolve both lateral and vertical changes. These quantitative models can then be used to inform several properties relevant for hydrological modelling (e.g. water content, permeability).</p><p>In this work the open-source software EMagPy is used to compare between EMI data collected with a multi-coil device (i.e. a single frequency device with multiple receiver coils) and a multi-frequency device (i.e. a single inter-coil distance and multiple frequencies). The latter instrument is easier to handle because of its shorter length and lower weight, and thus it is potentially more suitable for the rugged topography of mountain slopes. However it is important to compare the value of information (e.g. sensitivity patterns and data quality) obtained from both instruments.</p><p>To begin with, the performance of both devices is assessed using synthetic modeling. Following from this the analysis is focused on two mountainous catchments: one located in the Alpine region above 2000 m a.s.l., the other in a Mediterranean catchment in Southern Italy. Both sites have differing geological and hydrological conditions and provide a useful comparison to determine the suitability of multi-frequency and multi-coil devices, and highlight necessary considerations of EMI acquisition.</p>

<p>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:</p><p>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;</p><p>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;</p><p>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.</p><p>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.</p><p> </p>

Collecting the information regarding the sedimentary patterns of ancient tidal channels and providing a better understanding of their influence on the morphodynamic evolution of the lagoon environment, requires an expensive process that involves high resolution sediment coding. In this work we discuss the methods and results obtained from the electromagnetic survey carried out in the northern Venice Lagoon. We investigated meander deposit using two different conductivity meters: a multi-coil sensor and a multifrequency one. The aim of this study was to reveal the lateral and vertical structure of the meander body. The interpretation of the geophysical data has been correlated with borehole analysis, carried out from five sediment cores collected on the site area. In addition, the information regarding the architectural structure of the point bar deposit observed in the channel, from two seismic profile shown in the literature, has been considered. The results show that this method a...