Browsing by Author "Pirastru, Mario"

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    BEST-WR: An adapted algorithm for the hydraulic characterization of hydrophilic and water-repellent soils
    Di Prima, Simone; Stewart, Ryan D.; Abou Najm, Majdi R.; Ribeiro Roder, Ludmila; Giadrossich, Filippo; Campus, Sergio; Angulo-Jaramillo, Rafael; Yilmaz, Deniz; Roggero, Pier Paolo; Pirastru, Mario; Lassabatere, Laurent (Elsevier, 2021-12-01)
    Water-repellent soils usually experience water flow impedance during the early stage of a wetting process followed by progressive increase of infiltration rate. Current infiltration models are not formulated to describe this peculiar process. Similarly, simplified methods of soil hydraulic characterization (e.g., BEST) are not equipped to handle water-repellent soils. Here, we present an adaptation of the BEST method, named BEST-WR, for the hydraulic characterization of soils at any stage of water-repellency. We modified the Haverkamp explicit transient infiltration model, included in BEST for modeling infiltration data, by embedding a scaling factor describing the rate of attenuation of infiltration rate due to water repellency. The new model was validated using analytically generated data, involving soils with different texture and a dataset that included data from 60 single-ring infiltration tests. The scaling factor was used as a new index to assess soil water repellency in a Mediterranean wooded grassland, where the scattered evergreen oak trees induced more noticeable water repellency under the canopies as compared to the open spaces. The new index produced results in line with those obtained using the water drop penetration time test, which is one of the most widely test applied for quantifying soil water repellency persistence. Finally, we used BEST-WR to determine the hydraulic characteristic curves under both hydrophilic and hydrophobic conditions.
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    Coupling time-lapse ground penetrating radar surveys and infiltration experiments to characterize two types of non-uniform flow
    Di Prima, Simone; Giannini, Vittoria; Ribeiro Roder, Ludmila; Giadrossich, Filippo; Lassabatere, Laurent; Stewart, Ryan D.; Abou Najm, Majdi R.; Longo, Vittorio; Campus, Sergio; Winiarski, Thierry; Angulo-Jaramillo, Rafael; Del Campo, Antonio; Capello, Giorgio; Biddoccu, Marcella; Roggero, Pier Paolo; Pirastru, Mario (Elsevier, 2021-09-17)
    Understanding linkages between heterogeneous soil structures and non-uniform flow is fundamental for interpreting infiltration processes and improving hydrological simulations. Here, we utilized ground-penetrating radar (GPR) as a non-invasive technique to investigate those linkages and to complement current traditional methods that are labor-intensive, invasive, and non-repeatable. We combined time-lapse GPR surveys with different types of infiltration experiments to create three-dimensional (3D) diagrams of the wetting dynamics. We carried out the GPR surveys and validated them with in situ observations, independent measurements and field excavations at two experimental sites. Those sites were selected to represent different mechanisms that generate non-uniform flow: (1) preferential water infiltration initiated by tree trunk and root systems; and (2) lateral subsurface flow due to soil layering. Results revealed links between different types of soil heterogeneity and non-uniform flow. The first experimental site provided evidence of root-induced preferential flow paths along coarse roots, emphasizing the important role of coarse roots in facilitating preferential water movement through the subsurface. The second experimental site showed that water infiltrated through the restrictive layer mainly following the plant root system. The presented approach offers a non-invasive, repeatable and accurate way to detect non-uniform flow.