The analysis of infiltration, especially when infiltration experiments are used to estimate soil hydraulic properties, is becoming increasingly important for the geosciences community. Indeed, infiltration process is an important component of the hydrological cycle; it refers to the entry into the soil of water and all substances transported by it. Thus, estimates of soil infiltrability are mandatory key tasks to be performed on number of hydrologic, agronomic, ecological or environmental studies. Under natural conditions, infiltration is characterized by high spatial variability resulting from a high degree heterogeneity of both soil texture and structure. On the other hand, local infiltration experiments are sensitive to space-time variability of the unsaturated soil properties. High resolution infiltration measurement is crucial to properly describe and analyze soil water properties needed to model soil water flow. The aim of the session focus is on the principles, capabilities and applications of both infiltration techniques and models at different scales, including, but not limited to: - field infiltration measurements for a wide variety of infiltration devices, from the most simple to the most sophisticated and complete, combined to complementary information provided by other methods (i.e., TDR probes, GPR, ERT, etc.), - new or revisited numerical and analytical models to account for multiple-porosity, hydrophobicity, organic matter, or swelling on infiltration, clogging, biofilm development; and many other factors that are not taken into account in classic infiltration models, - estimation of soil hydraulic parameters, among which the saturated-unsaturated hydraulic conductivity and sorptivity which are fundamental in soil science. We will explore diverse topics of infiltration and interactions encompassing soil processes. The session is not limited by methodology or approach and we welcome studies including laboratory or numerical simulation of infiltration, in-situ studies of water and solutes infiltration. We welcome contributions from simulated and real data investigations in the laboratory or field, successful and failed case studies as well as the presentation of new and promising infiltration approaches.

Preferential and non-uniform flows are induced by biotic and abiotic factors and processes (roots, wet-dry and freeze-thaw cycles, lithology) as well as anthropogenic activities (e.g. tillage and cultivation, mining activity). In consolidated porous fractured systems, the vadose zone may reach a thickness of several hundred meters and preferential flow paths are commonly associated with discontinuities (fissures, fractures, etc). The understanding of preferential flow (PF) is of premium importance in relation to soil surface and catchment hydrology. PF can move a considerable amount of water and solutes (pollutants and bacteria) from the soil surface to groundwater bodies. PF shortens the residence time in the vadose zone and reduces pollutant contact with the soil reactive particles. Therefore, the importance of understanding preferential flow processes cannot be overstated, regarding the fate and transport of solutes, nutrients and contaminants in agricultural land, landscapes, catchments, mine waste covers and tailings storage facilities. This session welcomes studies on experimental and theoretical challenges aimed to identify, quantify, and model the physical processes involved in preferential flows and their impacts on mass transfers in porous media across scales (from pore scale to catchment scale):
• Understand the geometry and connectivity, formation and dynamics of fissure, fractures and macropores;
• Understand the effect of physical processes and geochemical processes on the dynamics of macropores and fracture networks;
• Develop and refine models for quantifying preferential flow, from pore scale to pedon scale and entire catchments and landscapes;
• Unpacking the pore structure of soil using new methods and approaches, including the use of non-Newtonian fluids, for improved characterization of heterogeneous soils and preferential flow.
• Effects of preferential flows on solute, nutrient or contaminant transport in the saturated and unsaturated zone;
• Coupling the physical processes of preferential flows and geochemical processes for improving the understanding of solute sorption and desorption, mineral precipitation and dissolution;
• Modelling of the effect of preferential flow on mass transport across scales, from pore scale to pedon scale and entire catchments and landscapes.

Soil structure and its stability determine soil physical functions and chemical properties such as water retention, hydraulic conductivity, susceptibility to erosion, and redox potentials. These soil physical and chemical characteristics are fundamental for biological processes, among them root penetration and organic matter and nutrient dynamics. The soil pore network forms the habitat for soil biota, which in turn actively reshape it according to their needs. The soil biota, root growth, land management practices like tillage and abiotic drivers (e.g. wetting/drying cycles) lead to a constant evolution of the arrangement of pores, minerals and organic matter. With this, also the soil functions and properties are perpetually changing. The importance of the interaction between soil structure (and thus soil functions) on one side and soil biology, climate and soil management on the other, is highlighted by recent research outcomes, which are based on advanced imaging techniques and novel experimental setups. Still, present studies have barely scratched the surface of what there is to discover.
In this session, we are inviting contributions on the formation and alteration of soil structure and its associated soil functions over time. Special focuses are on feedbacks between soil structure dynamics and soil biology as well as the impact of mechanical stress exerted by heavy vehicles deployed under land management operations. Further, we encourage submissions that are integrating complementary measurement techniques or aim at bridging different scales.

The hydrophysical and thermal properties of soils play a major role in current societal issues such as agricultural productivity, the preservation of water resources, gas and energy exchanges between soil and atmosphere and ultimately the protection of livelihoods. However, laboratory and field methods used to characterize soil properties remain questionable as to their suitability, and representativeness of the highly heterogeneous soil medium.
Moreover, reliable parameterization of key soil processes is important in land surface models. Parameter uncertainties, missing processes, process descriptions that lack reality, and the assumption that soil parameters remain constant in time, adversely impact the fidelity of flux- and state variable estimates. For example, in recent years, highly spatially resolved global data sets of soil properties have been developed for improved parameterization of soil hydraulic properties, yet they lack incorporation in Earth system models.
Also, while many pedotransfer functions exist to estimate the parameters that describe the hydrophysical and thermal soil characteristics, they remain globalizing approaches, based on limited available in-situ data, that are often dominated by certain regions and soil types. Hence, their usefulness is limited when it comes to assessing the impact of innovative practices that bring about changes in soil structure.
In this context, this session acknowledges that soil structure matters and invites contributions presenting new approaches to characterise the physical properties of soils using new sensors, new field and/or lab measurement techniques, as well as contributions illustrating comparative approaches between methods and/or laboratories.
This scientific session also welcomes contributions on improved parameterization of soil and critical zone processes. This session aims to bring together scientists from the climate- and soil-biogeosciences communities and to identify key shortcomings in current land surface models. Specifically, we welcome contributions that are already exploring the use of existing global datasets to advance soil model parameterization, including those embedded in weather forecast or climate models.
The session is part of the SOPHIE initiative (Soil Program on Hydro-Physics via International Engagement)
https://www.wur.nl/en/article/Soil-Program-on-Hydro-Physics-via-International-Engagement-SOPHIE.htm

In arid and semi-arid areas, the interaction between surface water management, irrigation practices, soil hydrologic dynamics and groundwater are key for sustainable water management, food production and for the resilience of agroecosystems. Their importance goes beyond the sole technological aspects, often being connected with some traditional techniques, part of local cultural heritage, to be faced with an (at least) interdisciplinary approach which involves also humanities. On the other hand, improper land and water management in those areas may contribute to soil degradation and groundwater exploitation. As an example, irrigation may lead to salinization of both the root-zone and shallow groundwater layers, with dramatic fallout on agricultural productivity, and overgrazing may lead soil to compaction with negative effects on the soil’s capability to buffer water.
This session presents contributions ranging from the understanding of the soil hydrological behaviour, including the mass fluxes between surface and groundwater, in arid and water—scarce environments; to the interaction between irrigation, soil hydrology and groundwater; and to the design and management of water harvesting and irrigation systems in arid and semi-arid regions, including oases. Particular attention will be given to the maintenance and improvement of traditional irrigation techniques as well as to precision irrigation techniques, also with local community involvement. Interdisciplinary contributions, which deal with different aspects and functions of the link between social dynamics, soil hydrology, groundwater management and irrigation techniques in arid environments, are encouraged.

This session deals with the use of geophysical methods for the characterisation of subsurface properties, states, and processes in contexts such as hydrology, agriculture, contaminant transport, etc. Geophysical methods potentially provide subsurface data with an unprecedented spatial and a high temporal resolution in a non-invasive manner. However, the interpretation of these measurements is far from straightforward in many contexts and various challenges still remain. Amongst these, the need for improved quantitative use of geophysical measurements in model conceptualisation and parameterisation, and the need to move quantitative hydrogeophysical investigations beyond the column and field scale towards the catchment scale. Therefore, we especially encourage submissions addressing advances in i) the acquisition, inversion and interpretation of geophysical data and other minimally invasive methods in a (contaminant) hydrological context, ii) model-data fusion including new concepts for joint and coupled inversion, and iii) petrophysical understanding linking hydrological and geophysical properties.