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In the Sahel region, agroforestry is a land-use system widely adopted as a more sustainable agricultural production system. In this type of system, woody perennials that are grown in association with agricultural crops and pastures, constitute spatially disconnected zones where microclimate and soil’s infiltrability, physical, chemical, and biological conditions are assumed locally improved. Particularly the stemflow concentrates a part of the intercepted rainfall from the canopies to the stems. Hence stemflow can induce preferential infiltration around the stem base and promote groundwater recharge.In the West African Sahel, Faidherbia albida (Delile) A.Chev. is commonly adopted as multi-purpose woody perennial in agroforestry systems. It is a deciduous tree with an inverse phenology as it loses the leaves during the rainy season. Although, the absence of leaves during the rainy season is expected to decrease the interception and to consequently decrease stemflow, evidence of stemflow at the base of F. albida trees were reported in the literature when the stems were partially covered with green leaves (Chinen, 2007).In this study, we carried out timelapse ground penetrating radar (GPR) surveys in conjunction with a simulated stemflow event to investigate stemflow-induced infiltration by an F. albida tree trunk and root system. We established a survey grid (2.1 m × 2.1 m) around an F. albida, consisting of twelve horizontal and ten vertical parallel survey lines with 0.3 m intervals between them. Two stemflow pulses, each of 20 L, were poured on the tree trunk using a PVC pipe with a 1-mm-diameter hole every 50 mm. The pipe was connected to a plastic funnel and positioned around the tree trunk at 0.4 m from the soil surface. One grid GPR survey was carried out before the stemflow simulation experiment. A total of 40 L of water was used during the experiment. A second survey was carried out after the injection of the first 20 L, while the last survey was carried out after the second stemflow pulse. We collected a total of 66 (3 GPR surveys × 22 survey lines) radargrams using a GSSI (Geophysical Survey System Inc., Salem, NH) SIR 3000 system with a 900-MHz antenna. We therefore obtained for each survey line a pre-wetting and two post-wetting radargrams. Next, we created other forty-four matrixes based on absolute differences between pre- and post-wetting amplitude values. Higher differenced values occurred because of amplitude changes and time shifts related to wave propagation.The analysis of the differentiated radargrams provided evidence of deep infiltration along the tap roots. The wetted zone extended mainly in-depth providing evidence of the potential role played by the F. albida trees in groundwater recharge processes due to their deep rooting, preferably reaching the groundwater table. Put all together, this study shows a first signal of the importance of accounting for stemflow infiltration in the water balance of agroforestry systems with F. albida trees.ReferencesChinen, T., 2007. An observation of surface runoff and erosion caused by acacia albida stemflow in dry savanna, in the south-western republic of Niger 10.

The hydrological response of steep slopes catchments is strongly conditioned by the connectivity of subsurface preferential flows. The objective of this research is to investigate the role played by stemflow infiltration in subsurface water flow dynamics, focusing on a forested hillslope located in an Aleppo pine Mediterranean forest (Pinus halepensis, Mill.) located at Sierra Calderona, Valencia province, Spain. We combined stemflow artificial experiments with ground-penetrating radar (GPR) techniques as a non-invasive method to investigate stemflow-induced preferential flow paths activated by different trees and the related hydrological connectivity at the hillslope scale. Our observations allowed us to identify different dynamics associated with the initiation of stemflow and then lateral preferential flow, including the activation of connected preferential flow paths in soils that received stemflow water from different trees. These observations provided empirical evidence of the role of stemflow in the formation of lateral preferential flow networks. Our measurements allow estimations of flow velocities and new insight on the magnitude of stem-induced lateral preferential flow paths. The applied protocol offers a simple, repeatable and non-invasive way to conceptualize hillslope responses to rainstorms.

Nature-based systems are being employed to allow stormwater to infiltrate directly in the soil, which is supposed to capture pollutants. To better track the evolution of such systems performances, in particular the infiltration and filtration performances, and to be able to optimize their management, these systems need to be better known. Currently, there is a lack of knowledge and methods regarding the characterization of the macropores and matrix contributions in infiltration and filtration of urban soils, whereas the quality of groundwater and the capacities of these systems are at stake. To tackle these limits, a large infiltrometer of 50 cm in diameter with two water-supply reservoirs of approximately 40 L each, was developed to characterize both hydrodynamic and nanotracers transfer parameters. Cumulative water infiltration was carried out at a constant hydraulic pressure head of 10 cm. Superparamagnetic iron oxide nanoparticles (SPIONs), which mimic both colloidal pollutants and bacteria flow behaviors in soils, were designed to be detectable by ground-penetrating radar (GPR). Fifty volumes of SPIONs solution (i.e., 50 x 5 mL at 3.35g/L) were injected into the ring and the GPR was passed along different survey lines around the ring several times during the infiltration experiment. GPR data was treated with ReflexW (Sandmeier Scientific Software, Karlsruhe, Germany) and Rockware (RockWare, Inc, 2015) to define a 3D block diagram of the infiltration bulb. The probability of presence of the nanoparticles was obtained from comparing the radargrams, before and after nanoparticle injection, by using two methods (Allroggen and Tronicke, 2015; Di Prima et al., 2020) on a R software (https://www.R-project.org/).The large infiltrometer device, compared with a smaller one (Di Prima et al., 2015), is proved effective for estimating water and transfer parameters. The dispersion of SPIONs gave an idea of the relative importance of the transfer through the soil macropores as compared to the soil matrix. The probability of SPIONs presence gave information on the filtration function of soils. The whole device application will be illustrated and discussed with regard to its use for the assessment of the infiltration and filtration functions of bio-infiltration systems. Allroggen, N., Tronicke, J., 2015. Attribute-based analysis of time-lapse ground-penetrating radar data. Geophysics 81, H1–H8. https://doi.org/10.1190/geo2015-0171.1Di Prima, S., Lassabatere, L., Bagarello, V., Iovino, M., Angulo-Jaramillo, R., 2015. Testing a new automated single ring infiltrometer for Beerkan infiltration experiments. Geoderma 262, 20–34. https://doi.org/10.1016/j.geoderma.2015.08.006Di Prima, S., Winiarski, T., Angulo-Jaramillo, R., Stewart, R.D., Castellini, M., Abou Najm, M.R., Ventrella, D., Pirastru, M., Giadrossich, F., Capello, G., Biddoccu, M., Lassabatere, L., 2020. Detecting infiltrated water and preferential flow pathways through time-lapse ground-penetrating radar surveys. Sci. Total Environ. 726, 138511. https://doi.org/10.1016/j.scitotenv.2020.1385

21 Pags.- 8 Figs.- 2 Tabls. © Author(s) 2023. This work is distributed under the Creative Commons Attribution 4.0 License., Sorptivity is one of the most important parameters for the quantification of water infiltration into soils. Parlange (1975) proposed a specific formulation to derive sorptivity as a function of the soil water retention and hydraulic conductivity functions, as well as initial and final soil water contents. However, this formulation requires the integration of a function involving hydraulic diffusivity, which may be undefined or present numerical difficulties that cause numerical misestimations. In this study, we propose a mixed formulation that scales sorptivity and splits the integrals into two parts: the first term involves the scaled degree of saturation, while the second involves the scaled water pressure head. The new mixed formulation is shown to be robust and well-suited to any type of hydraulic function – even with infinite hydraulic diffusivity or positive air-entry water pressure heads – and any boundary condition, including infinite initial water pressure head. Lastly, we show the benefits of using the proposed formulation for modeling water into soil with analytical models that use sorptivity., This work was performed within the INFILTRON project supported by the French National Research Agency. This research has been supported by the Agence Nationale de la Recherche (grant no. ANR-17-CE04-010).

Hydrological processes 37(6), e14928 (2023). doi:10.1002/hyp.14928, Published by Wiley, New York, NY

The permeable pavement is a compensatory drainage technique for urban waters that aims to control runoff and to ensure ideal hydrological conditions. This work had as main objectives to evaluate the infiltration capacity of a permeable pavement (PP) at real scale, through analytical and numerical modeling. It relies on water infiltration experiments and related modeling for the hydrodynamic characterization of the coating layer (saturated hydraulic conductivity, Ks , and sorptivity, S). A large panel of analytical and numerical models was considered, and several estimates were obtained. Then, the criteria for the evaluation of the maintenance requirement of the permeable pavements were computed for all the Ks -estimates considering the NCRS standards (assessment of permeability levels). The results indicated nice fits and accurate estimates for both the saturated hydraulic conductivity and the sorptivity. However, the Ks -estimates depended on the considered model and led to contrasting results in terms of classification. For 8 of the 9 models, the value of the Ks -estimate leads to the classification of “Group A” of the NCRS soil classification, meaning a very permeable material. In contrasts, the last method (numerical inverse modeling) classified the permeable pavement as “Group D”, i.e., soils with low permeability. Those results show the importance of the selection of characterization methods regarding the assessment of the hydrological classification of permeable pavements.

Infiltration into water repellent soils has been widely observed, quantified and documented. The modelling of water infiltration into water repellent soils is more rarely taken into account explicitly. In this study, we modelled water infiltration into water repellent soils considering explicitly the contact angle, with the geometrical pore model proposed and validated previously. The applied microscopical approach showed good agreement with macroscopical models and with experimental data. We firstly investigated the case of contact angles lower than 90°, for the cylindrical pore and pearl necklace (PN) models. The cumulative infiltrations were numerically generated versus contact angle and for different pore radii. Then, the modelled infiltration curves were fitted to the two-terms Philip equation and parameters S and A were evaluated versus contact angle. As predicted sorptivity S decreased with increasing contact angle, and the constant infiltration rate A increased with contact angle for both models. Then, the modelled data were fitted to the numerical solution of the Richards equation to derive the equivalent hydraulic parameters assuming van Genuchten model. The results showed that the contact angle decreased the saturated hydraulic conductivity and increased the parameter α. Lastly, our model was used to investigate strong water repellency with contact angles higher than 90°. Cumulative infiltration and related Philip parameters, S and A, were evaluated versus water pressure head at surface h0 and contact angles (between 90° and 96°). Our model may be used to predict water infiltration into water repellent soils for both moderate and strong water repellency, including fingering features

Infiltration trenches are compensatory techniques that have been settled up for decades. These aim to store the stormwater previously collected and infiltrate water into its banks. The objectives of the proposed study consist of modeling the water dynamics in an infiltration trench in order to evaluate its hydraulic performance. The studied trench is installed in the city of Recife (Pernambuco-Brazil, Brazil). We analyzed the response time of the infiltration system, the percentage of the infiltrated volume, and the dynamics of water storage processes for an extensive series of several rainfall events. We used the PULS method to model the events and quantify the contributions of each compartment to the water budget (infiltration, evaporation, etc.). Both observations and modeling demonstrated that the infiltration trench had a positive effect, with high performance, allowing the infiltrating of a large part of the drained volume. The infiltration trench achieved its objective of decreasing the volume drained on the surface. In this research, we also question the changes in the soil characteristics with time (in particular clogging of the banks) and the potential occurrence of preferential flow.

Stormwater management zones must enable water to infiltrate easily, primarily due to macropores, but little is known about the transport of pollutants through these macropores. Some coupled methods using, for example, dyes, disc, or ring infiltrometers were developed to give insight on the respective contributions of the macropores versus the matrix to the bulk infiltration. However, these methods do not visualize where and how water infiltrates. Besides, no information is given on the solute transfer in soils, whereas this issue is crucial regarding the quality of soils and groundwater. One of the goals of the national program INFILTRON (https://infiltron.org) project granted by the French national research agency is to develop superparamagnetic iron oxide nanoparticles (SPIONs) which mimic both pollutant and bacteria flow behavior in soils (Raimbault et al., 2021) and are detectable by ground-penetrating radar (GPR). Within its framework (Lassabatere et al., 2020), we aim to show how nano-tracers can help detect preferential treatment flows (lithological heterogeneity, root system) and quantify or qualify the pollutant transfer in heterogeneous soils. A specific device was designed and presented for the concomitant monitoring of water infiltration and nano-tracer injection. This specific infiltrometer involves two water supply reservoirs and a ring diameter of 50 centimeters. This device maintains a constant depth of water (10 cm) above the soil and delivers the water infiltration into the soil. Two rules posed on the reservoirs allow monitoring the water drop and computation of the cumulative infiltration. Fifty volumes of SPIONs solutions (5 mL of 3.35g/l SPIONs solution) were injected into the ring to maintain a constant concentration in the ring. GPR monitors the bulb of infiltrated water and SPIONs. GPR data is treated with ReflexW (©Sandmeier geophysical research) and RockWorks (RockWare®) software. Combining this specific prototype with the use of GPR for the detection of water and the SPIONs gives insight into the processes of infiltration and SPIONs transfer and localization in the soil. These data allow us to understand and model pollutant transfer into the vadose zone.Raimbault, J., Peyneau, P.-E., Courtier-Murias, D., Bigot, T., Gil Roca, J., Béchet, B., and Lassabatère, L.: Investigating the impact of exit effects on solute transport in macropored porous media, 2020, 1–20, https://doi.org/10.5194/hess-2020-494, 2020Lassabatere, L., De Giacomoni, A.-C., Angulo-Jaramillo, R., Lipeme Kouyi, G., Martini, M., Louis, C., Peyneau, P.-E., Rodriguez-Nava, V., Cournoyer, B., Aigle, A., and others: INFILTRON package for assessing infiltration & filtration functions of urban soils, in: EGU General Assembly Conference Abstracts, 11269, 2020. https://doi.org/10.5194/egusphere-egu2020-11269

Over the past two centuries, studying the infiltration process has received significant efforts resulting in numerous infiltration models being developed. These models depended on specific soil properties, and were influenced by initial and boundary conditions. They were also classified into two major categories: empirical and conceptual models, although the boundaries between those two categories can be debated for several models. The empirical models solved the infiltration problem by curve-fitting measured data into algebraic equations. In contrast, the conceptual approaches built on earlier concepts, mainly derived from the fundamental flow models, and then formulated analytical solutions applied to the infiltration problem. In this review, we create an inclusive survey covering the diverse spectrum of published infiltration modeling to understand the philosophy and evolution of those empirical and conceptual models across the years. After providing a full historical retrospective of infiltration models, we explored the model parameters and their evolution with time. We also reviewed the different methods applied to estimate the basic and common infiltration parameters, as well as the challenges that arise by such methods.

Sorptivity is a crucial parameter for modeling water infiltration into soils. Many works have related sorptivity to the soil hydraulic functions, i.e., the water retention and unsaturated hydraulic functions. Parlange's (1975) formulation is one of the most used to relate sorptivity to the soil hydraulic functions, allowing the direct computation of sorptivity as a function of the soil hydraulic parameters and initial and final water contents. On this basis, several works investigated the possibility of direct analytical relationships between sorptivity and the hydraulic shape and scale parameters (e.g., Lassabatere et al., 2021). So far, most of the studies have focused on single permeability soils with monomodal water retention and unsaturated hydraulic functions. However, the use of dual- or multi-permeability approaches is increasing in relation to the necessity to account for preferential flows in soils. The approach developed by (Gerke and van Genuchten, 1993) or (Pollacco et al., 2017) are examples of dual-permeability approaches and allow the modeling of preferential flows in soils. In the proposed study, we apply the formulation proposed by Parlange (1975) for the computation of sorptivity for dual-permeability soils, considering the approaches proposed by Gerke and van Genuchten (1993) and Pollacco et al. (2017). Our developments lead to a relation between the bulk sorptivity of the dual permeability soils to those of the matrix and the fast-flow compartments, plus additional terms. We end with the scaling of the proposed relation for investigating the effects of the matrix and fast-flow shape and scale parameters and the volumetric content occupied by the fast-flow compartment.ReferencesGerke, H. H. and van Genuchten, M. T.: A dual-porosity model for simulating the preferential movement of water and solutes in structured porous-media, 29, 305–319, 1993.Lassabatere, L., Peyneau, P.-E., Yilmaz, D., Pollacco, J., Fernández-Gálvez, J., Latorre, B., Moret-Fernández, D., Di Prima, S., Rahmati, M., Stewart, R. D., Abou Najm, M., Hammecker, C., and Angulo-Jaramillo, R.: Scaling procedure for straightforward computation of sorptivity, 2021, 1–33, https://doi.org/10.5194/hess-2021-150, 2021.Parlange, J.-Y.: On Solving the Flow Equation in Unsaturated Soils by Optimization: Horizontal Infiltration, 39, 415–418, 1975.Pollacco, J. A. P., Webb, T., McNeill, S., Hu, W., Carrick, S., Hewitt, A., and Lilburne, L.: Saturated hydraulic conductivity model computed from bimodal water retention curves for a range of New Zealand soils, 21, 2725–2737, https://doi.org/10.5194/hess-21-2725-2017, 2017.

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.

In the last decade, the development of methodologies based on Beerkan infiltration (ring or disk infiltrometry technique with null constant water head) analysis allows today to estimate the hydraulic properties of surface soils with increasing accuracy. In particular, the 3D model of Haverkamp et al. (1994) and its two-term (BEST methods) and four-term (4T) expansions (Moret-Fernández et al., 2020) have demonstrated their robustness. The analysis of the transient part of cumulative Beerkan infiltration allows the simultaneous estimation of the sorptivity S and the hydraulic conductivity at saturation Ks. Very recently presented, the sequential analysis (SAI) of Beerkan data (Moret and Fernandez et al., 2021) applied to stratified soils columns allows delimiting the part of the Beerkan infiltration curve governed by the upper layer and estimating its thickness. This approach opens new perspectives for using Beerkan water infiltration, especially for estimating the conductivity of the underlying porous medium. Numerical Beerkan infiltration of layered soils combination in 1D were produced using van Genuchten-Mualem model and Hydrus 1D software. Numerical curves were subject to SAI method to estimate the upper horizon soil hydraulic properties and the regime state of the infiltration flow allowed the estimation. Therefore, it is possible under certain assumptions to estimate the hydraulic conductivity of the underlying soil in 1D. This is the first step towards the determination of stratified soils hydraulic properties. This approach will allow new theoretical development for the extension to three-dimensional water infiltration into layered soils and relative hydraulic characterization of soil layering.Moret-Fernández, D., Latorre, B., López, M.V., Pueyo, Y., Lassabatere, Angulo-Jaramillo, R., Rahmati,M., Tormo, J., Nicolu, J.M. (2020). Three- and four-term approximate expansions of the Haverkamp formulation to estimate soil hydraulic properties from disc infiltrometer measurements. Hydrological Processes, 34 (26), 5543-5556. Haverkamp, R., Ross, P. J., Smettem, K. R. J., & Parlange, J. Y. (1994). Three‐dimensional analysis of infiltration from the disc infiltrometer: 2. Physically based infiltration equation. Water Resources Research, 30(11), 2931-2935.Moret-Fernández, D., Latorre, B., Lassabatere, L., Di Prima, S., Castellini, M., Yilmaz, D., & Angulo-Jaramilo, R. (2021). Sequential infiltration analysis of infiltration curves measured with disc infiltrometer in layered soils. Journal of Hydrology, 126542.

Made available in DSpace on 2022-04-28T19:44:52Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-02-01 Consiglio Nazionale delle Ricerche European Regional Development Fund Università degli Studi di Sassari Agence Nationale de la Recherche Ministero dell’Istruzione, dell’Università e della Ricerca 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. Department of Agricultural Sciences University of Sassari, Viale Italia, 39A Desertification Research Center University of Sassari, Viale Italia, 39 Univ Lyon Université Claude Bernard Lyon 1 CNRS ENTPE UMR5023 LEHNA Department of Architecture Design and Urban Planning University of Sassari, Via Piandanna, 4 School of Agriculture São Paulo State University (UNESP) Fazenda Experimental Lageado School of Plant and Environmental Sciences Virginia Polytechnic Institute and State University Department of Land Air and Water Resources University of California Department of Chemistry and Pharmacy University of Sassari, Via Piandanna 4 Research Group in Forest Science and Technology (Re-ForeST) Universitat Politècnica de València, Camí de Vera Institute of Sciences and Technologies for Sustainable Energy and Mobility (STEMS) National Research Council of Italy, Strada delle Cacce, 73 School of Agriculture São Paulo State University (UNESP) Fazenda Experimental Lageado Agence Nationale de la Recherche: ANR-17-CE04-0010 Ministero dell’Istruzione, dell’Università e della Ricerca: J54I18000120001

This research was funded by the Ministry of Business, Innovation and Employment's Endeavour Fund, through the Manaaki Whenua-led `Next Generation S-map' research programme, C09 x1612. We would like to thank from Manaaki Whenua - Landcare Research John Dando for the laboratory physical determinations, Veronica Penny for collecting soil cores and samples, and John Drewry for reviewing the manuscript. Mathieu Sellier from Civil Mechanical of the University of Canterbury (New Zealand) is also thanks for reviewing the manuscript., Hydraulic parameters define the water retention, theta( psi), and the unsaturated hydraulic conductivity, K(theta), functions. These functions are usually obtained by fitting experimental data using inverse modelling. The drawback of inverting the hydraulic parameters is that they suffer from non-uniqueness and the optimal hydraulic parameters may not be physical. To reduce the non-uniqueness, it is necessary to invert the hydraulic parameters simultaneously from observations of theta( psi) and K(theta), and ensure the measurements cover the full range of theta from saturated to oven dry. The challenge of using bimodal theta(psi) and K(theta) compared to unimodal functions is that it requires double the number of parameters, one set for the matrix and another set for the macropore domain. The objective of this paper is to address this shortcoming by deriving a procedure to reduce the number of parameters to be optimized to obtain a unique physical set of bimodal soil Kosugi hydraulic parameters from inverse modelling. To achieve this, we (1) derive residual volumetric soil water content from the Kosugi standard deviation parameter of the soil matrix, (2) derive macropore hydraulic parameters from the water pressure head threshold between macropore and matrix flow, and (3) dynamically constrain the Kosugi hydraulic parameters of the soil matrix. The procedure successfully reduces the number of optimized hydraulic parameters and dynamically constrains the hydraulic parameters without compromising the fit of the theta(psi) and K(theta) functions, and the derived hydraulic parameters are more physical. The robustness of the methodology is demonstrated by deriving the hydraulic parameters exclusively from theta(psi) and Ks data, enabling satisfactory prediction of K(theta) even when no additional K(theta) data are available., Ministry of Business, Innovation and Employment's Endeavour Fund C09 x1612

International audience; Soil hydraulic characterization is crucial to describe the retention and transport of water in soil, but current methodologies limit its spatial applicability. This paper presents a cost-effective general Beerkan Estimation of Soil Transfer parameters (BEST) methodology using single ring infiltration experiments to derive soil hydraulic parameters for any unimodal water retention and hydraulic conductivity functions. The proposed method relies on the BEST approach. The novelty lies in the use of Kosugi hydraulic parameters without need for textural in- formation. In addition, the method uses a quasi-exact formulation that is valid for all times, which avoids the use of approximate expansions and related inaccuracy. The new BEST methods were tested against numerically generated data for several contrasting synthetic soils, and the results show that these methods provide consis- tent hydraulic functions close to the target functions. The new BEST method is accurate and can use any water retention and hydraulic conductivity functions.

Sorptivity is a parameter of primary importance in the study of unsaturated flow in soils. This integral parameter is often considered for modeling the computation of water infiltration into vertical soil profiles (1D or 3D axisymmetric geometry). Sorptivity can be directly estimated from the knowledge of the soil hydraulic functions (water retention of hydraulic conductivity), using the integral formulation of Parlange (Parlange, 1975). However, it requires the prior determination of the soil hydraulic diffusivity and its numerical integration between the initial and the final saturation degrees, which may be tricky for some instances (e.g., coarse soil with diffusivity functions quasi-infinite close to saturation). In this paper, we present a specific scaling procedure for the computation of sorptivity considering slightly positive water pressure heads at the soil surface and initial dry conditions (corresponding to most water infiltration on the field). The square sorptivity is related to the square dimensionless sorptivity (referred to as cp parameter) corresponding to a unit soil (i.e., unit values of all the scaled parameters and zero residual water content) utterly dry at the initial state and saturated at the final state. The cp parameter was computed numerically and analytically for five current models: delta functions (Green and Ampt model), Brooks and Corey, van Genuchten-Mualem, van Genuchten-Burdine, and Kosugi models as a function of the shape parameters. The values are tabulated and can be easily used to determine any dimensional sorptivity value for any case. We propose brand-new analytical expressions for some of the models and validate previous formulations for the other models. Our numerical results also showed that the relation between the cp parameters and shape parameters strongly depends on the chosen model, with either increasing or decreasing trends when moving from coarse to fine soils. These results highlight the need for carefully selecting the proper model for the description of the water retention and hydraulic conductivity functions for the rigorous estimation of sorptivity. Present results show the need to understand better the hydraulic model's mathematical properties, including the links between their parameters, and, secondly, to better relate these properties to the physical processes of water infiltration into soils.

Hydrological models use soil hydraulic parameters to describe the storage and transmission of water in soils. Hydraulic parameters define the water retention, θ(ψ), and the hydraulic conductivity, K(θ), functions. These functions are usually obtained by fitting experimental data to the corresponding θ(ψ) and K(θ) functions. The drawback of deriving the hydraulic parameters by inverse modelling is that they suffer from equifinality or non-uniqueness, and the optimal hydraulic parameters are non-physical (Pollacco et al., 2008). To reduce the non-uniqueness, it is necessary to invert the hydraulic parameters simultaneously from observations of both θ(ψ) and K(θ), and ensure the measurements cover the full range of θ from fully saturated to oven dry, which requires expensive, labour-intensive measurements. We present a novel procedure to derive a unique, physical set of bimodal or dual permeabilityKosugi hydraulic functions, θ(ψ) and K(θ), from inverse modelling. The Kosugi model was chosen given its parameters have direct physical meaning to the soil pore-size distribution. The challenge of using bimodal functions is they require double the number of parameters (Pollacco et al., 2017), exacerbating the problem of non-uniqueness. To address this shortcoming, we (1) derive residual soil water content from the matrix Kosugi standard deviation, (2) derive macropore hydraulic parameters from the soil water pressure boundary between macropore and matrix, and (3) dynamically constraint the matrix Kosugi hydraulic parameters. We successfully reduce the number of hydraulic parameters to optimize and constrain the hydraulic parameters without compromising the fit of the θ(ψ) and K(θ) functions.The robustness of the methodology is demonstrated by deriving the hydraulic parameters exclusively from θ(ψ) and Ksdata, enabling satisfactory prediction of K(θ) without having measured K(θ) data. Moreover, having a reduced number of hydraulic parameters that are physical allows an improved characterization of hydraulic properties of soils prone to preferential flow, which is a fundamental issue regarding the understanding of hydrological processes. ReferencesPollacco, J.A.P., Ugalde, J.M.S., Angulo-Jaramillo, R., Braud, I., Saugier, B., 2008. A linking test to reduce the number of hydraulic parameters necessary to simulate groundwater recharge in unsaturated soils. Adv Water Resour 31, 355–369. https://doi.org/10.1016/j.advwatres.2007.09.002Pollacco, J.A.P., Webb, T., McNeill, S., Hu, W., Carrick, S., Hewitt, A., Lilburne, L., 2017. Saturated hydraulic conductivity model computed from bimodal water retention curves for a range of New Zealand soils. Hydrol. Earth Syst. Sci. 21, 2725–2737. https://doi.org/10.5194/hess-21-2725-2017

The 3-D Haverkamp et al. (1994) model for disc infiltrometer measures on homogeneous media involves the following parameters: the soil sorptivity, S, the saturated hydraulic conductivity, Ks, the β parameter and the A= (γ S2)/(rd*Δθ) term, where rd is the disc radius, Δθ is the soil water increase and γ is proportionality constant. Fixed β and A values are commonly used in most cases. S, and Ks can be estimated from the inverse analysis of a cumulative infiltration curve by fitting it the Haverkamp model. For practical reasons, Haverkamp implicit model is replaced by its 4-term (4T) approximate expansion for the transient state. The first part of this work analyzes the influence of layered soils on Ks and S estimates, and designs a new procedure, sequential Analysis of Infiltration curve (SAI), for treating infiltration curves impacted by soil layering. The SAI method analyzes a sequence of increasing dataset for a given infiltration curve and fits to the 4T expansions to estimate Ks, S. Then estimates and RMSE are reported as a function of the number of data points used for the fit. The method was applied on synthetic profiles with homogeneous loam soil, six layered profiles involving a 1, 2 and 3 cm thickness loam layer over silty or sandy loam soils, respectively. Erroneous estimates of Ks and S were obtained when the total infiltration curves were considered for the analysis, regardless of the presence of soil layering. In opposite, estimates were improved using the SAI method for the layered systems. The SAI method relies on the fact that the RMSE increases when the wetting front reaches the interface between the upper layer and the lower layer. Such increase allows (i) the detection of the soil heterogeneity, (ii) the determination of the optimum infiltration time, to, that corresponds to the minimum value of RMSE, and, (iii) accurate estimation the upper layer Ks and S.Taking use of the SIA procedure, the second part of this communication studied the relationship between β and A, and proposed a new procedure to improve the estimate of Ks and S and approach β. The analysis was applied on synthetic infiltration curves simulated on homogneneous and layered columns. The results showed that different combinations of β and A resulted in similar Ks. Overall, optimization of Ks, S and A for different β values showed that β had an important effect on A and Ks, but not on S and RMSE. We propose approaching the optimum β as the β for which is closer to zero, where A and Aexp are the optimized and measurable parameter, respectively. While the optimum β is calculated, Ks and S are computed by applying the optimum β to the respective quadratic β(Ks) and β(S) relationships. This methodology allowed improving the estimate of Ks giving good approaches of β (36% error) and omitting the erroneous praxis of using constant β and A values.Haverkamp, R., et al. 1994. 3. Water Resources Research 30, 2931–2935.

Preferential flow is more the rule than the exception. Water infiltration is often led by preferential flow due to macropores, specific soil structures (e.g., aggregates, macropore networks), or lithological heterogeneity (occurrence of materials with contrasting hydraulic properties). Water infiltration in soils prone to preferential flow strongly depends on soil features below the soil surface, but also the initiation of water infiltration at the surface. When the macropore networks are not dense, with only a few macropores intercepting the soil surface, water infiltration experiments with ring size in the order of 10-15 cm diameter may overlook sampling macropore networks during some infiltration runs, minimizing the effect of macropore flow on the bulk water infiltration at the plot scale.In this study, we investigated the effect of ring size on water infiltration into soils prone to preferential flow. We used two ring sizes: small (15 cm in diameter) and large (50 cm in diameter). By doing so, we hypothesized that the large rings, sampling a more representative soil volume, will maximize the probability to intercept and activate a macropore network. In contrast, the small rings may activate the macropore network only occasionally, with other infiltration runs mainly sampling the soil matrix. Thus, the small rings are expected to provide more variable results. On the other hand, the large rings are expected to provide more homogeneous results in line with the soil's bulk infiltration capability, including all pore networks at the plot scale.Three different sites were sampled with varying types of preferential flow (macropore-induced versus lithological heterogeneity induced). The experimental plan included inserting large rings at several places in the experimental sites with a dozen small rings nearby to sample the same soil. All the rings were submitted to a similar positive constant water pressure head at the soil surface. The cumulative infiltrations were then monitored and treated with BEST algorithms to get the efficient hydraulic parameters. Note that the cumulative infiltration could not be compared directly since lateral water fluxes varied in extent and geometry between the different ring sizes. The impacts of the ring size on the magnitude of cumulative infiltration and related estimated hydraulic parameters were discussed. Our results demonstrated the impact of ring size but also the dependency of such effect on the site and the type of flow.Our results contribute to understanding preferential flow in heterogeneous soils and the complexity of its measure using regular water infiltration devices and protocols.

Time-lapse ground penetrating radar (GPR) surveys in conjunction with automated single-ring infiltration experiments can be used for non-invasive monitoring of the spatial distribution of infiltrated water and for generating 3D representations of the wetted zone. In this study we developed and tested a protocol to quantify and visualize water distribution fluxes under unsaturated and saturated conditions into layered soils. We carried out a gridded GPR survey on a 0.3-m thick sandy clay loam layer underlain by a restrictive limestone layer at the Ottava experimental station of the University of Sassari (Sardinia, IT). We firstly established a survey grid (1 m × 1 m), consisting of six horizontal and six vertical parallel survey lines with 0.2 m intervals between them. The field survey then consisted of six steps, including i) a first GPR survey, ii) a tension infiltration experiment conducted within the grid and aimed at activating only the soil matrix, iii) a second GPR survey aimed at highlighting the amplitude fluctuations between repeated GPR radargrams of the first and second surveys, due to the infiltrated water moving within the matrix flow region, iv) a single-ring infiltration experiment of the Beerkan type carried out within the grid on the same infiltration surface using a solution of brilliant blue dye (E133) and aimed to activate the whole pore network, v) a third GPR survey aimed to highlight the amplitude fluctuations between repeated GPR radargrams of the first and third surveys, due to the infiltrated water moving within the whole pore network (both matrix and fast-flow regions), and vi) the excavation of the soil to expose the wetted region. The shapes of the 3D diagrams of the wetted zones facilitated the interpretation of the infiltrometer data, allowing us to resolve water infiltration into the layered system. Finally, we used the infiltrometer data in conjunction with the Beerkan estimation of soil transfer parameter (BEST) method to determine the following capacitive indicators of soil physical quality of the upper soil layer: air capacity AC (m3 m–3), plant-available water capacity PAWC (m3 m–3), relative field capacity RFC (–), and soil macroporosity pMAC (m3 m–3). Results showed that the investigated soil was characterized by high soil aeration and macroporosity (i.e., AC and pMAC) along with low values for indicators associated with microporosity (i.e., PAWC and RFC). These findings suggest that the upper soil layer facilitates root proliferation and quickly drains excess water towards the underlying limestone layer, and, on the contrary, has limited ability to store and provide water to plant roots. In addition, the 3D diagram allowed the detection of non-uniform downward water movement through the restrictive limestone layer. The detected difference between the two layers in terms of hydraulic conductivity suggests that surface ponding and overland flow generation occurs via a saturation-excess mechanism. Indeed, percolating water may accumulate above the restrictive limestone layer and form a shallow perched water table that, in case of extreme rainfall events, could rise causing the complete saturation of the soil profile.

Stewart and Abou Najm (2018) developed a comprehensive model (SA model) for single ring infiltration that consists of a couple of two-terms explicit infiltration equations similar, in form, to the approximate expansions proposed by Haverkamp et al. (1994) (HV model). Application of SA model requires the transition time, τcrit, from transient to steady state to be known a-priori or establishing a constraint among the four constants that figure in the infiltration equations. Estimation of soil saturated hydraulic conductivity, Ks, and capillary length, λ, from single ring infiltration measurements also needs a scaling parameter referred to “a” to be known. SA model assumes this scaling parameter as a constant and fixes its value at a = 0.45. However, there is evidence that a cannot be considered a constant independent of soil type and initial water content.This study investigates some open issues related to the use of the SA model for single ring infiltration: 1) how comparable is τcrit with the maximum time, tmax, that separates transient from steady state condition in HV model; 2) how the scaling parameter a depends on different experimental conditions and how it can be related to HV parameters.Preliminary theoretical considerations showed that the two characteristic times (τcrit and tmax) are related and, for relatively dry initial conditions, parameter a depends only on the soil type and ring radius being maximum for small ring radii or soils with high capillarity (a = 1) and minimum for large rings or coarse soils (a = 0.467).An optimization procedure, with a constraint among the four infiltration constants, was applied to fit the SA model to both analytical and experimental infiltration data to derive τcrit and the associated value of a.The analytical data confirmed that the ratio τcrit/tmax was constant and equal to 1.495, regardless the combination of soil, ring diameter and initial water saturation. The calculated a values varied between 0.706 and 0.904, with a mean equal to a = 0.807, and were independent of the initial water content for saturation degrees up to approximately 0.50.Application of the optimization procedure to field data was problematic given it was successful only in 29 out of 70 infiltration tests. Fixing τcrita-priori could be advisable in this case and it was shown that two alternative empirical criteria for selecting τcrit yielded a values differing by a nearly negligible mean factor of 1.10 and significantly correlated to one another (R2 = 0.997).However, a rather high percentage of a values (45.5%) were greater than the theoretical maximum value (a = 1), and therefore were physically implausible. Excluding these values from the analysis, the mean a parameter (a = 0.735) was close to that estimated by the successful applications of the optimization procedure (a = 0.673).Therefore, consistent results were obtained by field and analytical data with a values intermediate between the suggested values in the literature (a = 0.45 and 0.91). These findings can inform parameterization choices for others working with infiltration models, and should reduce uncertainty during interpretation of infiltration measurements.

Research over the past several decades has shown that preferential flow is more the rule than the exception. However, our collective understanding of preferential flow processes has been limited by a lack of suitable methods to detect and visualize the initiation and evolution of non-uniform wetting at high spatial and temporal resolutions, particularly in real-world settings. In this study, we investigate water infiltration initiation by tree trunk and root systems. We carried out time-lapse ground penetrating radar (GPR) surveys in conjunction with a simulated stemflow event to provide evidence of root-induced preferential flow and generate a three-dimensional representation of the wetted zone.We established a survey grid (3.5 m × 5 m, with a local slope of 10.3°), consisting of ten horizontal and thirteen vertical parallel survey lines with 0.5 m intervals between them. The horizontal lines were downslope-oriented. The grid was placed around a Quercus suber L. We collected a total of 46 (2 GPR surveys × 23 survey lines) radargrams using an IDS (Ingegneria Dei Sistemi S.p.A.) Ris Hi Mod v. 1.0 system with a 900-MHz antenna mounted on a GPR cart. Two grid GPR surveys were carried out before and after the artificial stemflow experiment. In the experiment, we applied 100 L of brilliant blue dye (E133) solution on the tree trunk. The stemflow volume of 100 L corresponded to 63.2 mm of incident precipitation, considering a crown projected area of 201 m2 and a 1.3% conversion rate of rainfall to stemflow. Trench profiles were carefully excavated with hand tools to remove soil and detect both root location and size and areas of infiltration and preferential pathways on the soil profile.The majority (84.4%) of artificially applied stemflow infiltrated into the soil, while the remaining 15.6% generated overland flow, which was collected by a small v-shaped plastic channel placed into a groove previously scraped on the downhill side of the tree. The 3D diagram clearly demarcated the dimension and shape of the wetted zone, thus providing evidence of root-induced preferential flow along coarse roots. The wetted zone extended downslope up to a horizontal distance of 3 m from the trunk and down to a depth of approximately 0.7 m. Put all together, this study shows the importance of accounting for plant and trees trunk and root systems when quantifying infiltration.

Infiltration into hydrophobic soils has been widely observed, quantified and documented in many situations and several climates (DeBano, 2000; Angulo-Jaramillo et al., 2016).The modelling of water ...

International audience; Due to the high costs associated with the control of soil erosion, the precise selection of practical techniques towards this end is a prerequisite for sustainable land management. For the proper application of anti-erosion measures, a good knowledge of the behavior of soil erosion and hydrological properties is required. Research has indicated that biochar (BC) and polyacrylamide (PAM) are important soil amendments to enhance the physical and hydrological characteristics of soil. However, little is known about the response and mechanisms underlying the wearing away of Marl and Loess erosion-prone soils treated with individually and with a com- bination of BC and PAM. Therefore, we tested the effectiveness of these anti-erosion techniques on the variability of 1) hydrological components (i.e., time to runoff, the runoff coefficient, and infiltration), 2) runoff quality components (i.e., pH and electrical conductivity (EC)), and 3) erosion components (i.e., upward-splash, down- ward-splash, net-splash erosion, soil loss, and sediment concentration) at two locations with the Marl and Loess soils under rainfall simulation conditions. The study treatments consisted of control (200 ml water), BC (800 g m− 2), PAM (2 g m− 2), and BC (800 g m− 2) + PAM (2 g m− 2). The treatments were sprayed uniformly over the small plots (0.3 × 0.5 × 0.5 m in dimension; 0.25 m2 in area) with a slope of 20% using three replicates. Rainfall with an intensity of 50 mm h− 1 for 0.5 h was applied. The results showed that (a) the use of PAM alone delayed the time to runoff with a rate of 41.4% compared to the control treatment in the Marl soil, and all treatments delayed the time to runoff for the Loess soil (BC = 37.1% and PAM = BC + PAM = 12.9%); (b) among the study treatments, PAM had the greatest effect as it decreased the runoff coefficient by 2.47% and 13.67%, and improved infiltration by 0.02% and 0.13% in Marl and Loess soils, respectively; (c) BC and BC + PAM increased the pH values of the runoff whereas the application of PAM partially reduced the pH compared to the control plot in both the soils studied; (d) the application of BC and BC + PAM significantly (p < 0.05) increased the EC of runoff released from both tested soils. In contrast, PAM had the least influence on the EC of the runoff compared to the control condition; (e) the maximum effect on the reduction of soil loss was attributed to BC for Marl and Loess soils with rates of − 14.07% and − 83.21%, respectively. Additionally, the maximum benefit of the reduction in sediment concentration was attributed to PAM (-14.87%) and BC (− 78.35%), respectively, in Marl and Loess soils; (f) all treatments reduced the upward-splash, downward-splash, and the net-splash erosion for both soils studied in the range of − 13.69% (BC + PAM in Loess soil) to − 73.68% (BC in Marl soil) in comparison with the control treatment.

International audience; Comprehensive infiltration models can simultaneously describe transient and steady-state infiltration behaviors, and therefore can be applied to a range of experimental conditions. However, satisfactory model accuracy re- quires proper parameterization, including estimating the transition time from transient to steady-state flow conditions (τcrit). This study focused on improving the estimation of two parameters – τcrit and a second constant called a – used in a comprehensive, explicit, two-term model for single ring infiltration (hereafter referred to as the SA model). Different studies have recommended that a should be as low as 0.45 to as high as 0.91. Furthermore, τcrit is often obtained a-priori by assuming that steady-state conditions are reached before the end of an infiltration run. However, there has not been a systematic analysis of those terms for different soils and infiltration conditions. To investigate these open issues related to the use of the SA model, here we introduce a novel, iterative method for estimating τcrit and the parameter a. We then applied this method to both analytical and experimental infiltration data, and compared it with two existing empirical methods. The analytical infil- tration experiments showed that τcrit was approximately 1.5 times larger than the maximum validity time of a similar two-term transient infiltration model. Further, the iterative method for obtaining τcrit had minimal effects on the a term, which varied between 0.706 and 0.904 and was larger for finer soils and when small water sources were used. Application of the proposed method was less efficient with experimental data. Only ~ 33% of the experiments yielding plausible estimates of a (i.e., a < 1), indicating that these infiltration model parameters often have high uncertainty. The successful runs indicated that a depended on the rate at which the initial infiltration rate approached the final infiltration rate. Depending on the fitting algorithm used, a had mean values of 0.74–0.78, which were intermediate between those suggested by previous studies. Altogether, these findings expand the applicability of the SA model by providing new methods for estimating τcrit and by showing that a does not need to be fixed a-priori. We expect that these advances will result in more reliable estimations of soil hydrodynamic parameters, including hydraulic conductivity.

The understanding of hydrological processes requires the investigation of preferential flows. In particular, the infiltration compartment is strongly affected by preferential flows. Recently, Lassabatere et al. (2014) proposed a model for the analytical modelling of the infiltration impacted by preferential flow. These authors extended the model developed by Haverkamp et al. (1994) for single permeability soils to the case of dual permeability soils. However, this model remains implicit, requiring an inversion procedure for the quantification of the bulk cumulative infiltration. Such an implicit feature prevents from direct computation and may annoy any fellow who wants a direct and simple computation procedure. In this paper, we develop two approximate expansions for both transient and steady states. For that, we use the expansions proposed by Haverkamp et al. (1994) for single permeability systems. These expansions are written for each compartment of the dual permeability soils, i.e. the matrix and the fast-flow regions and are combined for the computation of the bulk infiltration. After formulation of these expansions, these are assessed in terms of their capability to accurately reproduce the complete implicit model. Their validity time intervals are also determined and discussed. The main limitation for the use of these expansions results from the fact that the time intervals that define the transient and steady states are contrasted between the matrix and the fast-flow regions. However, some domain of validity can be defined allowing the use of these approximate expansions.Haverkamp, R., Ross, P. J., Smettem, K. R. J. and Parlange, J. Y.: 3-Dimensional analysis of infiltration from the disc infiltrometer .2. Physically-based infiltration equation, Water Resour. Res., 30(11), 2931–2935, 1994.Lassabatere, L., Angulo-Jaramillo, R., Soria-Ugalde, J. M., Simunek, J. and Haverkamp, R.: Numerical evaluation of a set of analytical infiltration equations, Water Resour. Res., 45, W12415, doi:doi:10.1029/2009WR007941, 2009.

Soil sorptivity is one of the key hydraulic parameters for modelling water infiltration into soil. It quantifies the capacity of a soil to infiltrate water by capillarity. Several formulations, based on various models, have been proposed to compute it from the water retention and the unsaturated hydraulic conductivity functions. All these formulations use the integration of the product of either the hydraulic conductivity or diffusivity function with the flux concentration function. The integration can be performed either over an interval of water pressure head or water content, yielding two equal values. However, the expression of the integral as a function of water pressure head may involve a huge or even infinite interval, which can be numerically difficult to handle. In opposite, the expression of the integral as a function of water content involves the integration of a diverging function (diffusivity) over a large interval, which is also troublesome from a numerical point of view. In this paper, we provide a new expression for sorptivity by cutting the integral in two parts, in order to involve only the integration of a finite function over a finite interval. The dependency of the integral on the flux concentration function is also investigated.

Nowadays soil erosion control using different amendments has grown up worldwide. However, the application of transformed materials like biochar has not been adequately studied. In the same vein, the application of biochars produced from waste materials that harm nature, and impose cost to managers and producers is a valuable approach for optimal utilization of the resources. Towards this, the performance of biochar produced from deleterious raw vinasse as the main by-product of sugarcane industries in controlling soil splash and interrill erosions on two marl and loess soils from Iran was investigated. The study was performed in 0.5 m×0.5 m plots in three replicates installed in the field with a slope steepness of 25% subjected to a simulated rainfall with an intensity of 50 mm h-1 and 0.5 h duration. Analysis of the results obtained from the splash and interrill erosions during the rainfall-runoff process showed that biochar decreased soil loss compared to the control plot on Marl soil but to a small extent (p > 0.05). However, the plot treated with biochar on the loess soil revealed significant (p

Soil hydraulic characterization is crucial to describe the retention and transport of water in soil, but current methodologies limit its spatial applicability. This work presents a cost-effective general Beerkan Estimation of Soil Transfer parameters (BEST) methodology using single ring infiltration experiments to derive soil hydraulic parameters for any type of unimodal water retention and hydraulic conductivity functions. The proposed method relies on the BEST approach. The novelty lies in the use of Kosugi hydraulic parameters without need for textural information. Kosugi functions were chosen because they are based on physical principles (log-normal distribution for pore size distributions). A link between the Kosugi parameters (i.e., relationship between σ and hkg) was introduced to reduce the number of parameters estimated and to avoid the need for information on the soil texture. This simplifies the procedures and avoids sources of errors related to the use of pedotransfer functions as for the previous BEST methods. Lastly, the method uses a quasi-exact formulation that is valid for all times, instead of the approximate expansions previously used, avoiding related inaccuracy and allowing the use of any infiltration data encompassing or not both transient and steady states. The new BEST methods were tested against numerically generated data for several contrasting synthetic soils, and the results show that these methods provide consistent hydraulic functions close to the target functions. The new BEST method is accurate and can use any type of water retention and hydraulic conductivity functions (Fernández-Gálvez et al., 2019). ReferenceFernández-Gálvez, J., Pollacco, J.A.P., Lassabatere, L., Angulo-Jaramillo, R., Carrick, S., 2019. A general Beerkan Estimation of Soil Transfer parameters method predicting hydraulic parameters of any unimodal water retention and hydraulic conductivity curves: Application to the Kosugi soil hydraulic model without using particle size distribution data. Adv. Water Resour. 129, 118–130. https://doi.org/10.1016/j.advwatres.2019.05.005

Cardoon (Cynara cardunculus L.) is a promising energy crop for marginal areas in Mediterranean environment. Temporary intercropping with cover crops can provide multiple services such as weed suppression, additional and diversified biomass production and soil physical quality (SPQ) improvement.A number of studies have demonstrated that the Beerkan estimation of soil transfer parameters (BEST) method appears promising for assessing SPQ in agricultural soils, given that it allows the entire determination of the water retention and hydraulic conductivity curves, and the derivation of both static and dynamic SPQ indicators in the field. However, BEST is suitable only for single-permeability (SP) soils. Lassabatere et al. (2019) designed a method for the hydraulic characterization of dual-permeability (DP) soils named BEST-2K to address the case of the soils prone to preferential flow. DP models are increasingly adopted in soil science to take better account of water flow dynamics in heterogeneous soils. Moreover, recent investigations suggested that a comprehensive assessment of SPQ of agricultural soils also involving DP approaches may substantially improve our capacity to evaluate the effect of specific management practices on key “domain-oriented” processes. Indeed, DP models assume that soil encompass two domains, including the matrix and the fast-flow domain that respectively host the smallest and the largest pores. While in the matrix domain the intra-aggregate pores constitutes the primary source of plant-available water and nitrous oxides, in the fast-flow domain the inter-aggregate pores are the primary region for root-essential air, carbon dioxide generation and nutrient leaching losses (Reynolds, 2017).We investigated the effects of temporary intercropping with cover crops belonging to different functional groups on SPQ. In October 2019, an experimental trial intercropping Cynara cardunculus cv Bianco Avorio with four different cover types (3 cover crops: Vicia villosa Roth. cv Haymaker Plus, Eruca sativa L. cv Nemat and Camelina sativa (L.) Crantz. cv Italia and spontaneous weeds) was set up at the Ottava experimental station of the University of Sassari (Sardinia, IT).The new BEST-2K method was used for assessing SPQ of the different intercropping systems. At this aim, we carried out multi-tension infiltration experiments in order to selectively activate only the matrix or the whole pore network, and for the characterization of the water retention and hydraulic conductivity functions of matrix and fast-flow domains. Then, we used these functions to determine SPQ indicators for the two domains. A zero-point scenario (1 month after sowing) has been already drawn. The field measurements will be repeated in summer after the harvest of the above-ground biomass of both cardoon and cover crops.ReferencesLassabatere, L., Di Prima, S., Bouarafa, S., Iovino, M., Bagarello, V., Angulo-Jaramillo, R., 2019. BEST-2K Method for Characterizing Dual-Permeability Unsaturated Soils with Ponded and Tension Infiltrometers. Vadose Zone Journal 18. https://doi.org/10.2136/vzj2018.06.0124Reynolds, W.D., 2017. Use of bimodal hydraulic property relationships to characterize soil physical quality. Geoderma 294, 38–49. https://doi.org/10.1016/j.geoderma.2017.01.035

Preferential flow is more the rule than the exception, in particular during water infiltration experiments. In this study, we demonstrate the potential of GPR monitoring to detect preferential flows during water infiltration. We monitored time-lapse ground penetrating radar (GPR) surveys in the vicinity of single-ring infiltration experiments and created a three-dimensional (3D) representation of infiltrated water below the devices. For that purpose, radargrams were constructed from GPR transects conducted over two grids (1 m × 1 m) before and after the infiltration tests. The obtained signal was represented in 3D and a threshold was chosen to part the domain into wetted and non-wetted zones, allowing the determination of the infiltration bulb. That methodology was used to detect the infiltration below the devices and clearly pointed at nonuniform flows in correspondence with the heterogeneous soil structures. The protocol presented in this study represents a practical and valuable tool for detecting preferential flows at the scale of a single ring infiltration experiment.

The extension of urban and peri-urban areas and the related artificialization of soils drastically impacts the water cycle as well as biogeochemical cycles. In particular, the sealing of soils with impervious surfaces such as roads increases runoff and decreases concomitant infiltration. At the catchment scale, more significant amounts of stormwater must be collected and managed to prevent from flooding urban areas and mitigate discharge to the environment. Sustainable Urban Drainage Systems (SUDS) were developed to alleviate these problems. These systems allow the restoration of one of the main functions of urban and peri-urban soils, i.e., infiltrating stormwater. They simultaneously reduce the risk of flooding and increase groundwater recharge. Another essential service must be ensured and optimized: the removal of pollutants from infiltrating water by the soil, to avoid the degradation of the quality of the groundwater.The INFILTRON project aims to design a methodology for the assessment of infiltration and filtration of pollutants by SUDS. The project is a collaboration of many partners, with expertise in soil physics, urban hydrology, nanoparticle engineering, and modeling, to engineer a specific device for the simultaneous monitoring of water infiltration and pollutant filtration. This infiltration device both infiltrates water and injects nanoparticles (NPs) into the soil. It was sized to account for preferential flow, which is known to have a significant impact on infiltration and pollutant transfer. The engineered NPs were designed to be detectable in the ground using ground-penetrating radar (GPR) and to mimic the transfer of nano-pollutants (emerging pollutants, bacteria, etc.) commonly found in real stormwater. An infiltration-filtration model was developed to interpret the experimental data and to quantify two indicators for the assessment of water infiltration and pollutant filtration. INFILTRON will provide a very interesting toolbox for practitioners and stakeholders for the evaluation of the infiltration and filtration functions of not only SUDS within the framework of stormwater management, but also anthropized soils within the management of urban and peri-urban areas.

Recently, cities growth has enhanced economic development but also generates different problems that affect the population such as stormwater drainage. It is known that the area available for water infiltration decrease in these urban centers generating scenarios of high vulnerability and risk of flooding associated with extreme weather events of precipitation. Therefore, an alternative is the implementation of Sustainable Urban Drainage systems (SUDs) that allows high efficiency in the control and local infiltration of rainwater. SUDs are often built with technosoils from the recycling of materials from different industries, for which it is necessary to study their hydraulic and solute retention properties. Indeed, one of the functions of SUDs must therefore be the retention of pollutants before they reach the groundwater. Therefore, this research aimed to evaluate the retention capacity of metallic solutes Pb and Cu in technosoils (compacted mixture of sand, loam and rice husk ash) proposed for SUDs in Bogota, Colombia. A research work was conducted by combining adsorption isotherms measurements, unsaturated column breakthrough flow experiments and numerical modeling with RETC, STANMOD and HYDRUS 1D models. Adsorption isotherm can be described satisfactorily using the Freundlich and Langmuir models. Additionally, unsaturated soil column leaching tests (ISO/TS S1268-3) allows estimation of solute diffusion through the soil profile. A multi-reaction model (MRM) and convection dispersion flow model reveal non-linear and non-equilibrium in the movement of solute in soil. Moreover, there is a competition for adsorption of metal ions in the technosoil profile; the order of selectivity of heavy metals in the active sites of the microporal network will be Pb+2> Cu+2, so that these technosoil is a favorable material in heavy metals retention.

The macroscopic capillary length is a critical parameter for the modeling of infiltration in single-ring experiments. Current methods to quantify this parameter either require multiple infiltration experiments, thus increasing effort and potential for error, or laboratory characterization that does not reflect field condition. We propose a simple field method for the estimation of the macroscopic capillary length, λc, from Beerkan runs (single-ring infiltration experiment with measurements of initial and saturated soil water contents). In the proposed method, we use the final portion of the cumulative infiltration, corresponding to the steady state of the water infiltration, to develop a reliable predictor of λc. The proposed model was validated using analytically generated data along with an experimental database that included 433 Beerkan runs from a wide range of conditions and types of soils. The analytical validation demonstrated the reliability of the proposed λc estimates for different soil textures and initial soil water contents. Altogether, the proposed method constitutes a simple solution for estimating λc, and it can improve our ability to estimate Ks in the field.

International audience; We present a new open-source and modular instrumentation package composed of up to ten automatic in- filtrometers connected to data acquisition systems for automatic recording of multiple infiltration experiments. The infiltrometers are equipped with differential transducers to monitor water level changes in a Mariotte re- servoir, and, in turn, to quantify water infiltration rates. The data acquisition systems consist of low-cost components and operate on the open-source microcontroller platform Arduino. The devices were tested both in the laboratory and on different urban and agricultural soils in France and India. More specifically, we tested three procedures to treat the transducers readings, including a filtering algorithm that substantially improved the ability to determine cumulative infiltration from raw data. We combined these three procedures with four methods for estimating the soil parameters from infiltrometer data, showing pros and cons of each scenario. We also demonstrated advantages in using the automatic infiltrometers when infiltration measurements were hin- dered by: i) linearity in cumulative infiltration curves owing to gravity-driven flow, ii) an imprecise description of the transient state of infiltration, and iii) the occurrence of soil water repellency. The use of the automatic infiltrometers allows the user to obtain more accurate estimates of soil hydraulic parameters, while also reducing the amount of effort needed to run multiple experiments.

International audience; Controlling soil erosion, especially in its initial stages, is greatly important in natural resources management. Con- sequently, the present research aimed to control splash and interrill erosion in two soil types (marl at Marzan- Abad and loess at Maraveh-Tapeh sites in northern Iran) using biochar (BC) and polyacrylamide (PAM). We established 0.5 × 0.5-m plots and applied BC (800 g·m−2), PAM (2 g·m−2), and BC + PAM (800 g·m−2- + 2 g·m−2) with control plots and three replications on a slope of ~25%. We used a rainfall simulator to achieve rainfall intensity of 50 mm·h−1 with 30-min duration in the experiments. Analysis of the results obtained from the variables of splash and interrill erosion during the rainfall-runoff process showed that the PAM significantly (p ≤ 0.05) increased all study variables of splash erosion. For interrill erosion, it reduced the variables of soil loss and sediment concentration. However, the difference was not significant (p N 0.05) compared to the control plot and runoff from the two treatment sites increased relative to that from the control plots. The plot treated with BC showed decreased runoff volume, runoff coefficient, and soil loss compared to the control plot at the Marzan- Abad site, but the differences were not statistically significant (p N 0.05). However, the plot in which loess soil was treated with BC at the Maraveh-Tapeh site exhibited considerably (p ≤ 0.05) increased runoff and soil loss compared to the control plot. The entire results verified a wide range for benefit reduction of study treatments from +25.09 to −37.49% for runoff and from +38.59 to −231% for soil loss with more effectiveness for Maraveh- Tapeh Loess soil as well as combined application of BC and PAM. These findings contribute to improved under- standing of proper application of soil amendments to control runoff and soil loss in loam and loess soils.