Papers by Claude Hammecker
Infiltration into water repellent soils has been widely observed, quantified and documented. The ... more 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 numerical solution of 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 h 0 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. 1 Introduction Water repellent soils are widely distributed all over the world, in many different climates, and in different types of soils
Infiltration into water repellent soils has been widely observed, quantified and documented. The ... more 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 numerical solution of 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 h 0 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. 1 Introduction Water repellent soils are widely distributed all over the world, in many different climates, and in different types of soils
In North Thailand land use/-cover change quickly especially in steep agrosystem land. Under rainf... more In North Thailand land use/-cover change quickly especially in steep agrosystem land. Under rainfall simulation, we are looking at the effect of the topographic situation along the slope and catena using 24 microplots of 1m2 each located down, middle, up and top of the slope. We quantified seed dispersion, soil detachment, soil losses and runoff processes for two soil treatment: tradition cropping and with biochar amendments.
Sorptivity is one of the most important parameters for the quantification of water infiltration i... more 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, h → −∞. Lastly, we show the benefits of using the proposed formulation for modeling water into soil with analytical models that use sorptivity.
Environmental Science and Pollution Research
-Les bilans thermiques et l'investigation complète de l'écoulement d'air sur une plaque d'acier n... more -Les bilans thermiques et l'investigation complète de l'écoulement d'air sur une plaque d'acier noir épaisse verticale chauffée à flux de chaleur uniforme (1000 à 8000W.m-2) sont obtenus par méthode thermoanémométrique et pyrométrie IR. Divers modèles physiques résolus au moyen d'un code de calcul commercial (FLUENT) sont ensuite comparés aux valeurs expérimentales. Nomenclature b épaisseur de plaque chauffée, m U m vitesse verticale maximum, m/s d distance entre microthermocouples, m x distance verticale au bord d'attaque, m G k production turbulente motrice, kg.m-1 .s-3 y distance horizontale à la plaque, m Gr x nombre de Grashof local gβ 0 (T w-T 0)x 3 /ν f 2 Symboles grecs h c coefficient d'échange convectif, W.m-2 .K-1
Sorptivity is one of the most important parameters for the quantification of water infiltration i... more 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 the hydraulic diffusivity, which may be undefined or present numerical difficulties that cause numerical misestimations. In this 5 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 functions-even with infinite hydraulic diffusivity or positive air-entry water pressure heads-and any boundary condition, including infinite initial water pressure head, h → −∞.
Soil erosion due to land use change and consequently biodiversity loss are major concerns in agri... more Soil erosion due to land use change and consequently biodiversity loss are major concerns in agricultural areas. However, the link between runoff, soil loss and plant dispersion by water also called hydrochory is not yet well understood, especially in tropical climate. The displacement of native plant seeds on the soil surface by runoff may be influenced by soil properties and by agricultural practices. This may in return affect or modify biodiversity in agroecosystems.This is why we propose to study the processes affecting seed displacement by runoff in steeply sloping maize field affected by rainfall and tillage erosion in Northern Thailand.After a first study under rainfall simulation in situ (Janeau et al. 2022), we present here a two years study under natural rainfall to assess the role of position in the catena and soil properties on seed displacement, soil loss and nutrient losses. We used 24 plots of 1 m2 located at four positions in the catena. Two treatments were tested: (...
Advances in Unsaturated Soils, 2013
Waste and Biomass Valorization, Aug 3, 2023
Archives of Agronomy and Soil Science, Jul 25, 2022
Applied Soil Ecology, Apr 1, 2022
Journal of Arid Environments
Despite the large contribution of macropores made by soil engineers to the soil macroporosity and... more Despite the large contribution of macropores made by soil engineers to the soil macroporosity and water infiltration, few studies have addressed the specific contribution of soil engineer groups, dynamics of biopores and their efficiency in conducting water. Thus, we aimed to investigate the link between soil macrofauna, soil biopores and water infiltration under different pedoclimatic conditions. To do so, we conducted an experimentation in twelve study sites with a large longitudinal gradient from France to Vietnam. The experiment consisted in the field incubation of repacked soil in cores (15 cm in height and 15 cm in diameter) and controlling the activity of soil engineers in the manner of litter bag. For each site, soil columns were: (i) covered with a mesh (200µm) or not and (ii) with or without addition of organic residues to the soil surface. After 12 months, we measured (i) the 3D organization of biopores by X-ray computed tomography and (ii) the saturated hydraulic conduc...
In Northeast Thailand, large areas of lowlying paddy fields are subjected to soil degradation via... more In Northeast Thailand, large areas of lowlying paddy fields are subjected to soil degradation via excess salt content, which affects rice cultivation. This process is mainly attributed to the rising of saline aquifers due to prior deforestation, in a geological context, including large amounts of evaporites. In discharge areas.iextrerne situations have developed with an accumulation of continuous salt crusts and land has been abandoned. The paper reveals that the local occurrence of saline crusts in the dry season could be linked to geological heterogeneity, aquifer levels, the proximity of an impermeable layer at the soil profile scale, and agricultural practices. If agricultural practices can lead to heterogeneity from one field to the other, they can hardly be considered as a distribution factor of salinity inside the same field where practices are homogenous. Geological heterogeneity of material can be found at very local scales especially in lowlying conditions, but do not explain why for the same quality of underground water and the same aquifer level, salt surface contents can vary in the soil within a distartce of a few meters. If the presence of saline crusts is evidence of soil degradation by salinity phenomena at a field scale, little is known about the internal distribution of salinity in the soil in connection with surface phenomena. The objectives of the present work were to study the soil spatial characteristics linked to an area of saline crusts and to examine the reasons for the spreading of salt crusts in conditions where agricultural practices and aquifer salinity are homogeneous.. 30.
Light textured sandy soils are ubiquitous throughout the tropics and constitute an important soil... more Light textured sandy soils are ubiquitous throughout the tropics and constitute an important soil resource on which millions are dependent upon for their livelihoods. Spanning a range of rainfall regimes from the arid to the humid tropics, they present unique sustainability and environmental challenges to resource managers. Over the course of the symposium papers were presented on topics that focused on the physical, chemical and biological attributes of these soils as well as the important social and economic consequences of utilizing this resource. Sandy soils are characterised by the predominance of rigid coarse particles that are inevitably associated with small amounts of clay minerals. These physical attributes contribute to the significant spatial and temporal variability that offers opportunities for greater use of spatial statistics in managing this variability. The inability of these soils to buffer changes in physical, chemical and biological predisposes them to accelerated rates of degradation. A common thread in all of the presentations highlight large differences in soil behaviour associated with minor changes in intrinsic soil properties that cannot be entirely attributed to natural heterogeneity. This may in part be due to the precision and quality of analytical tools used to quantify clay and organic matter quantity and quality, bulk density, pore size distribution or continuity, and sand size distribution. Improved sandy soils characterization would lead to a better understanding of processes of soil change, a better classification of relevant factors into a hierarchical system and finally, to more precise management recommendation that would enhance the sustainable utilization of these soil. Physical, chemical and biological characteristics of sandy soils often act as a severe limitation in crop production. Their sandy nature; low organic carbon content; high hydraulic conductivity rates; low nutrient and water supply capacity; limited buffering capacity; and inadequate biological diversity invariable necessitate high levels of external inputs. This has potential environmental implications under high rainfall or irrigated agriculture, elevated costs of production and very low levels of efficiency. By manipulating the constituent components of the soil through the addition and conservation of organic matter or through the physical application of organic waste and clay materials, the potential productivity of these soils can be realized. There are thus significant opportunities in developing innovative management strategies that enhance the productivity of these systems under the diverse range of climatic conditions in which these soils occur. Any innovation must integrate not only the limited potential of the tropical sandy soils but also the socioeconomic situation of the farmers. Within the tropics, these soils are predominantly occupied by resource poor and often marginalized communities that have limited capacity to address the aforementioned biophysical challenges. There is an urgent need for the disciplines of soil science, agronomy and the social sciences to come together to address these challenges in a holistic manner that effectively result in uplifting the livelihoods of the poorest. This is by no means a trivial task, but one that takes innovation and commitment by governments and leaders. I am confident that your collective wisdom and expertise provide a firm footing to build this strategy. I wish you well in your endeavour and look forward to seeing the output of this symposium. Thank you.
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Papers by Claude Hammecker