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A. Ünal Sorman - One of the best experts on this subject based on the ideXlab platform.
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Research Note: Determination of Soil Hydraulic Properties using pedotransfer functions in a semi-arid basin, Turkey
Hydrology and Earth System Sciences Discussions, 2004Co-Authors: M. Tombul, Z. Akyürek, A. Ünal SormanAbstract:Spatial and temporal variations in Soil Hydraulic Properties such as Soil moisture q(h) and Hydraulic conductivity K(q) or K(h), may affect the performance of hydrological models. Moreover, the cost of determining Soil Hydraulic Properties by field or laboratory methods makes alternative indirect methods desirable. In this paper, various pedotransfer functions (PTFs) are used to estimate Soil Hydraulic Properties for a small semi-arid basin (Kurukavak) in the north-west of Turkey. The field measurements were a good fit with the retention curve derived using Rosetta SSC-BD for a loamy Soil. To predict parameters to describe Soil Hydraulic characteristics, continuous PTFs such as Rosetta SSC-BD (Model H3) and SSC-BD-q33q1500 (Model H5) have been applied. Using Soil Hydraulic Properties that vary in time and space, the characteristic curves for three Soil types, loam, sandy clay loam and sandy loam have been developed. Spatial and temporal variations in Soil moisture have been demonstrated on a plot and catchment scale for loamy Soil. It is concluded that accurate site-specific measurements of the Soil Hydraulic characteristics are the only and probably the most promising method to progress in the future. Keywords: Soil Hydraulic Properties, Soil characteristic curves, PTFs
Harry Vereecken - One of the best experts on this subject based on the ideXlab platform.
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Characterization of Soil Hydraulic Properties using microwave radiometry and ground-penetrating radar
2015Co-Authors: François Jonard, Lutz Weihermüller, Mike Schwank, Harry Vereecken, Sébastien LambotAbstract:Knowledge of Soil Hydraulic Properties is necessary for accurate modeling of water and energy fluxes at the land surface. The objective of this study was to investigate the feasibility of remotely infering key Soil Hydraulic Properties from ground-penetrating radar (GPR and radiometer data.
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Effect of Soil Hydraulic Properties on the relationship between the spatial mean and variability of Soil moisture
Journal of Hydrology, 2014Co-Authors: Gonzalo Martínez García, Yakov Pachepsky, Harry VereeckenAbstract:Summary Knowledge of spatial mean Soil moisture and its variability over time is needed in many environmental applications. We analyzed dependencies of Soil moisture variability on average Soil moisture contents in Soils with and without root water uptake using ensembles of non-stationary water flow simulations by varying Soil Hydraulic Properties under different climatic conditions. We focused on the dry end of the Soil moisture range and found that the magnitude of Soil moisture variability was controlled by the interplay of Soil Hydraulic Properties and climate. The average moisture at which the maximum variability occurred depended on Soil Hydraulic Properties and vegetation. A positive linear relationship was observed between mean Soil moisture and its standard deviation and was controlled by the parameter defining the shape of Soil water retention curves and the spatial variability of saturated Hydraulic conductivity. The influence of other controls, such as variable weather patterns, topography or lateral flow processes needs to be studied further to see if such relationship persists and could be used for the inference of Soil Hydraulic Properties from the spatiotemporal variation in Soil moisture.
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Geostatistical co-regionalization of Soil Hydraulic Properties in a micro-scale catchment using terrain attributes
Geoderma, 2005Co-Authors: Michael Herbst, Bernd Diekkrüger, Harry VereeckenAbstract:Any effort of distributed hydrological modeling requires the spatially distributed input of Soil Hydraulic Properties and Soil thickness. Most of the hydrological models are sensitive concerning these Soil Properties, thus the use of point measurements and co-variables should be optimized for a most accurate spatial prediction. During this study, we focus on the use of terrain attributes as co-variables. In order to determine the dependencies between the Soil Properties and topography, we derived 17 terrain attributes for a small rural catchment (28.6 ha). Correlation statistics between these terrain attributes and Soil Hydraulic Properties calculated from measured grain size distribution and organic carbon content with pedo-transfer functions were used to identify terrain attributes as co-variables for the spatial prediction of the Soil Properties. We detected in particular for the following terrain attributes a high prediction potential for Soil Properties: relative elevation, slope of the catchment area, radiation angle and morphometric units such as slope elements. We also compared the performance of multiple regression, ordinary kriging, external drift kriging and regression kriging model C to estimate the spatial distribution of topSoil and subSoil Hydraulic Properties and horizon thickness. The prediction errors for the spatial structure of Soil Hydraulic Properties according to Mualem/Van Genuchten and horizon thickness were quantified by a cross validation procedure. We determined the regression kriging model C as the most appropriate method with, on average, the smallest prediction errors and because the resulting spatial structure corresponds to recent models of Soil Properties spatial structure. Compared to ordinary kriging without co-variables, the spatial prediction of Soil Properties could be improved with up to 15% by using terrain attributes as co-variables.
Willibald Loiskandl - One of the best experts on this subject based on the ideXlab platform.
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temporal dynamics of Soil Hydraulic Properties and the water conducting porosity under different tillage
Soil & Tillage Research, 2011Co-Authors: Andreas Schwen, Gernot Bodner, Graeme D. Buchan, P Scholl, Willibald LoiskandlAbstract:Abstract Soil Hydraulic Properties are subject to temporal changes as a response to both tillage and natural impact factors. As the temporal and spatial variability might exceed cultivation-induced differences, there is a need to better differentiate between those influence factors. Thus, the objective of the present study was to assess the impact of different tillage techniques – conventional (CT), reduced (RT), and no-tillage (NT) – on the Soil Hydraulic Properties and their temporal dynamics. On a silt loam Soil, tension infiltrometer measurements were obtained frequently over two consecutive years. The data was analyzed in terms of the near-saturated Hydraulic conductivity, inversely estimated parameters of the van Genuchten/Mualem (VGM) model, and the water-conducting porosity. Our results show that the near-saturated Hydraulic conductivity was in the order CT > RT > NT, with larger treatment-induced differences where water flow is dominated by mesopores. The VGM model parameterαVG was in the order CT
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Modeling Soil Water Dynamics with Time-Variable Soil Hydraulic Properties
2009Co-Authors: Andreas Schwen, Gernot Bodner, Andrea Schnepf, Daniel Leitner, Gerhard Kammerer, Willibald Loiskandl, Boku ViennaAbstract:Modeling Soil water dynamics requires an accurate description of Soil Hydraulic Properties, i.e. the retention and Hydraulic conductivity functions. Generally, these functions are assumed to be unchanged over time in most simulation studies. However, there is extensive empirical evidence that Soil Hydraulic Properties are subject to temporal changes. In this paper, we implemented temporal changes in the Soil Hydraulic Properties in a Richards' equation simulation of Soil water dynamics. Based on repeated measurement data of the Soil water retention curve over a vegetation period, we compared the impact of using constant vs. temporally changing Hydraulic functions on water flow simulation for different tillage methods. We observed distinct differences in the Soil water content between the simulations for all tillage methods. The results show the remarkable effect of time-variable retention parameters on the Soil water dynamics for tilled and non-tilled top Soils.
G.b. Chirico - One of the best experts on this subject based on the ideXlab platform.
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Uncertainty in predicting Soil Hydraulic Properties at the hillslope scale with indirect methods
Journal of Hydrology, 2007Co-Authors: G.b. Chirico, H. Medina, N. RomanoAbstract:Several hydrological applications require the characterisation of the Soil Hydraulic Properties at large spatial scales. Pedotransfer functions (PTFs) are being developed as simplified methods to estimate Soil Hydraulic Properties as an alternative to direct measurements, which are unfeasible for most practical circumstances. The objective of this study is to quantify the uncertainty in PTFs spatial predictions at the hillslope scale as related to the sampling density, due to: (i) the error in estimated Soil physico-chemical Properties and (ii) PTF model error. The analysis is carried out on a 2-km-long experimental hillslope in South Italy. The method adopted is based on a stochastic generation of patterns of Soil variables using sequential Gaussian simulation, conditioned to the observed sample data. PTFs of Vereecken [Vereecken, H., Diels, J., van Orshoven, J., Feyen, J., Bouma, J., 1992. Functional evaluation of pedotransfer functions for the estimation of Soil Hydraulic Properties. Soil Sci. Soc. Am. J. 56, 1371???1378] and HYPRES [Wo¨sten, J.H.M., Lilly, A., Nemes, A., Le Bas, C., 1999. Development and use of a database of Hydraulic Properties of European Soils. Geoderma 90, 169???185] are applied. The two PTFs estimate reliably the Soil water retention characteristic even for a relatively coarse sampling resolution, with prediction uncertainties comparable to the uncertainties in direct laboratory or field measurements. The uncertainty of Soil water retention prediction due to the model error is as much as or more significant than the uncertainty associated with the estimated input, even for a relatively coarse sampling resolution. Prediction uncertainties are much more important when PTF are applied to estimate the saturated Hydraulic conductivity. In this case model error dominates the overall prediction uncertainties, making negligible the effect of the input error
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Uncertainty in predicting Soil Hydraulic Properties at the hillslope scale with indirect methods
Journal of Hydrology, 2006Co-Authors: G.b. Chirico, H. Medina, Nunzio RomanoAbstract:Summary Several hydrological applications require the characterisation of the Soil Hydraulic Properties at large spatial scales. Pedotransfer functions (PTFs) are being developed as simplified methods to estimate Soil Hydraulic Properties as an alternative to direct measurements, which are unfeasible for most practical circumstances. The objective of this study is to quantify the uncertainty in PTFs spatial predictions at the hillslope scale as related to the sampling density, due to: (i) the error in estimated Soil physico-chemical Properties and (ii) PTF model error. The analysis is carried out on a 2-km-long experimental hillslope in South Italy. The method adopted is based on a stochastic generation of patterns of Soil variables using sequential Gaussian simulation, conditioned to the observed sample data. The following PTFs are applied: Vereecken’s PTF [Vereecken, H., Diels, J., van Orshoven, J., Feyen, J., Bouma, J., 1992. Functional evaluation of pedotransfer functions for the estimation of Soil Hydraulic Properties. Soil Sci. Soc. Am. J. 56, 1371–1378] and HYPRES PTF [Wosten, J.H.M., Lilly, A., Nemes, A., Le Bas, C., 1999. Development and use of a database of Hydraulic Properties of European Soils. Geoderma 90, 169–185]. The two PTFs estimate reliably the Soil water retention characteristic even for a relatively coarse sampling resolution, with prediction uncertainties comparable to the uncertainties in direct laboratory or field measurements. The uncertainty of Soil water retention prediction due to the model error is as much as or more significant than the uncertainty associated with the estimated input, even for a relatively coarse sampling resolution. Prediction uncertainties are much more important when PTF are applied to estimate the saturated Hydraulic conductivity. In this case model error dominates the overall prediction uncertainties, making negligible the effect of the input error.
M.r. Khaledian - One of the best experts on this subject based on the ideXlab platform.
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No-Tillage impacts on Soil Hydraulic Properties compared with conventional tillage
Journal of Biological & Environmental Sciences, 2012Co-Authors: M.r. Khaledian, J.c Mailhol, Pierre RuelleAbstract:Soil Hydraulic Properties are very important in precision irrigation, water and solute transport and irrigation scheduling. Tillage can change near surface Soil Hydraulic Properties. In this study Beerkan methodwas used to better understand tillage and no-tillage impacts on transmission Properties of topSoil. Beerkan is a simple in situ method using a single ring to measure infiltration rate. This method depends on an algorithm namely BEST to estimate Soil Hydraulic Properties. This study was carried out at Cemagref experimental station in Montpellier in the South-eastern France. Three different infiltration measurement series were done in both no-tillage and conventional tillage treatments. The first infiltration measurement series was performed after harvest of durum wheat; the second one was performed after sowing of corn and finally the last one was performed after the harvest of corn. By using those three series as input data, BEST model estimated saturated Hydraulic conductivity (Ks), sorptivity, the mean characteristics of Hydraulically functional pore size and capillary length. The results indicate that after harvest, Hydraulic Properties were not significantly different; however after sowing of corn, Ks was significantly higher in CT system (p
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Temporal variability in Soil Hydraulic Properties under drip irrigation
Geoderma, 2009Co-Authors: Ibrahim Mubarak, J.c Mailhol, Pierre Ruelle, Rafael Angulo-jaramillo, Pascal Boivin, M.r. KhaledianAbstract:Predicting Soil Hydraulic Properties and understanding their temporal variability during the irrigated cropping season are required to mitigate agro-environmental risks. This paper reports field measurements of Soil Hydraulic Properties under two drip irrigation treatments, full (FT) and limited (LT). The objective was to identify the temporal variability of the Hydraulic Properties of field Soil under high-frequency water application during a maize cropping season. Soil Hydraulics were characterized using the Beerkan infiltration method. Seven sets of infiltration measurements were taken for each irrigation treatment during the cropping season between June and September 2007. The first set was measured two weeks before the first irrigation event. The results demonstrated that both Soil porosity and Hydraulic Properties changed over time. These temporal changes occurred in two distinct stages. The first stage lasted from the first irrigation event until the root system was well established. During this stage, Soil porosity was significantly affected by the first irrigation event, resulting in a decrease in both the saturated Hydraulic conductivity Ks and the mean pore effective radius ξm and in an increase in capillary length αh. These Hydraulic parameters reached their extreme values at the end of this stage. This behavior was explained by the Hydraulic compaction of the surface Soil following irrigation. During the second stage, there was a gradual increase in both Ks and ξm and a gradual decrease in αh when the effect of irrigation was overtaken by other phenomena. The latter was put down to the effects of wetting and drying cycles, Soil biological activity and the effects of the root system, which could be asymmetric as a result of irrigation with only one drip line installed for every two plant rows. The processes that affected Soil Hydraulic Properties in the two irrigation treatments were similar. No significant change in ξm and αh was observed between FT and LT. However, as a result of daily wetting and drying cycles, which were strongest in LT, the Soil in this treatment was found to be more conductive than that of FT. This showed that most of the changes in pore-size distribution occurred in the larger fraction of pores. The impact of these temporal changes on the dimensions of the wetting bulb was studied using a simplified modeling approach. Our results showed that there were marked differences in the computed width and depth of wetting bulb when model input parameters measured before and after irrigation were used. A temporal increase in capillary length led to a more horizontally elongated wetting bulb. This could improve both watering and fertilization of the root zone and reduce losses due to deep percolation. As a practical result of this study, in order to mitigate agro-environmental risks we recommend applying fertilizers after the restructuration of tilled Soil. Further studies using improved models accounting for temporal changes in Soil Hydraulic Properties are needed.
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Temporal variability in Soil Hydraulic Properties under drip irrigation
Geoderma, 2009Co-Authors: Ibrahim Mubarak, J.c Mailhol, Pierre Ruelle, Rafael Angulo-jaramillo, Pascal Boivin, M.r. KhaledianAbstract:International audiencePredicting Soil Hydraulic Properties and understanding their temporal variability during the irrigated cropping season are required to mitigate agro-environmental risks. This paper reports field measurements of Soil Hydraulic Properties under two drip irrigation treatments, full (FT) and limited (LT). The objective was to identify the temporal variability of the Hydraulic Properties of field Soil under high-frequency water application during a maize cropping season. Soil Hydraulics were characterized using the Beerkan infiltration method. Seven sets of infiltration measurements were taken for each irrigation treatment during the cropping season between June and September 2007. The first set was measured two weeks before the first irrigation event. The results demonstrated that both Soil porosity and Hydraulic Properties changed over time. These temporal changes occurred in two distinct stages. The first stage lasted from the first irrigation event until the root system was well established. During this stage, Soil porosity was significantly affected by the first irrigation event, resulting in a decrease in both the saturated Hydraulic conductivity Ks and the mean pore effective radius ξm and in an increase in capillary length αh. These Hydraulic parameters reached their extreme values at the end of this stage. This behavior was explained by the “Hydraulic” compaction of the surface Soil following irrigation. During the second stage, there was a gradual increase in both Ks and ξm and a gradual decrease in αh when the effect of irrigation was overtaken by other phenomena. The latter was put down to the effects of wetting and drying cycles, Soil biological activity and the effects of the root system, which could be asymmetric as a result of irrigation with only one drip line installed for every two plant rows. The processes that affected Soil Hydraulic Properties in the two irrigation treatments were similar. No significant change in ξm and αh was observed between FT and LT. However, as a result of daily wetting and drying cycles, which were strongest in LT, the Soil in this treatment was found to be more conductive than that of FT. This showed that most of the changes in pore-size distribution occurred in the larger fraction of pores. The impact of these temporal changes on the dimensions of the wetting bulb was studied using a simplified modeling approach. Our results showed that there were marked differences in the computed width and depth of wetting bulb when model input parameters measured before and after irrigation were used. A temporal increase in capillary length led to a more horizontally elongated wetting bulb. This could improve both watering and fertilization of the root zone and reduce losses due to deep percolation. As a practical result of this study, in order to mitigate agro-environmental risks we recommend applying fertilizers after the restructuration of tilled Soil. Further studies using improved models accounting for temporal changes in Soil Hydraulic Properties are needed
