Evaluation of LEACHMN under dryland conditions. I. Simulation of water and solute transport

2005 ◽  
Vol 85 (2) ◽  
pp. 223-232 ◽  
Author(s):  
O. O. Akinremi ◽  
Y. W. Jame ◽  
C. A. Campbell ◽  
R. P. Zentner ◽  
C. Chang ◽  
...  
Keyword(s):  
Soil Water ◽  
Chloride Concentration ◽  
Preliminary Evaluation ◽  
Retention Data ◽  
Soil Water Retention ◽  
Modified Model ◽  
Water Redistribution ◽  
Fallow System ◽  
Using Data ◽  
Water Transmission

The ability to simulate the dynamics of soil nitrogen under field conditions will aid our understanding of the nitrogen cycle. Our objective was to test the water and solute components of LEACHMN using data obtained from a field lysimeter study conducted on a medium-textured soil in southwestern Saskatchewan, Canada. Our preliminary evaluation of LEACHMN showed that the retentivity and conductivity functions used in this model were not appropriate for our soil as the original model permitted water transmission through the soil profile too rapidly. We, therefore, incorporated the van Genuchten retentivity function into LEACHMN and used the same soil water retention data to generate the van Genuchten parameters. The modified model was able to reproduce changes in water and chloride concentration after minimal calibration. Overall, the value of 0.45 used for the pan coefficient for soil under fallow and 12 mm used for dispersivity produced a realistic estimation of changes in water and chloride within the soil in the 2 yr of the field experiment. The model reproduced soil water redistribution in a fallow system. There was a tendency to under-estimate soil water content during dry periods, mainly as a result of the model’s tendency to over-estimate evaporation. While the centre of mass of chloride was correctly estimated, the model under-estimated the maximum depth of chloride penetration due to a slight tendency to over-estimate evaporation. Based on our statistical and graphical evaluation of LEACHMN, the modified model is adequate for our subsequent nitrate leaching study. Key words: LEACHMN, lysimeter, dryland, water, chloride, nitrate

scholarly journals Changes in the Structure of a Nigerian Soil under Different Land Management Practices

2015 ◽  
Vol 39 (3) ◽  
pp. 830-840 ◽  
Author(s):  
Joshua Olalekan Ogunwole ◽  
Luiz Fernando Pires ◽  
Bello Muhammed Shehu
Keyword(s):  
Soil Water ◽  
Land Management ◽  
Water Retention ◽  
Management Practices ◽  
Cropping System ◽  
Retention Data ◽  
Soil Water Retention ◽  
Physical Quality ◽  
Bush Fallow ◽  
Fallow System

Quantification of soil physical quality (SPQ) and pore size distribution (PSD) can assist understanding of how changes in land management practices influence dynamics of soil structure, and this understanding could greatly improve the predictability of soil physical behavior and crop yield. The objectives of this study were to measure the SPQ index under two different land management practices (the continuous arable cropping system and natural bush fallow system), and contrast the effects of these practices on the structure of PSD using soil water retention data. Soil water retention curves obtained from a pressure chamber were fitted to van Genuchten’s equation, setting m (= 1-1/n). Although values for soil bulk density were high, soils under the continuous arable cropping system had good SPQ, and maintained the capacity to support root development. However, soils under the natural bush fallow system had a worse structure than the continuous arable system, with restrictions in available water capacity. These two management systems had different PSDs. Results showed the inferiority of the natural bush fallow system with no traffic restriction (which is the common practice) in relation to the continuous arable cropping system in regard to physical quality and structure.

scholarly journals Prediction of soil water retention properties using pore-size distribution and porosity

2013 ◽  
Vol 50 (4) ◽  
pp. 435-450 ◽  
Author(s):  
Christopher T.S. Beckett ◽  
Charles E. Augarde
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Soil Water ◽  
Water Retention ◽  
Adsorbed Water ◽  
Retention Data ◽  
Soil Water Retention ◽  
Pore Size Distributions ◽  
Water Retention Properties

Several models have been suggested to link a soil's pore-size distribution to its retention properties. This paper presents a method that builds on previous techniques by incorporating porosity and particles of different sizes, shapes, and separation distances to predict soil water retention properties. Mechanisms are suggested for the determination of both the main drying and wetting paths, which incorporate an adsorbed water phase and retention hysteresis. Predicted results are then compared with measured retention data to validate the model and to provide a foundation for discussing the validity and limitations of using pore-size distributions to predict retention properties.

scholarly journals Investigation into water retention behaviour of deformable soils

2013 ◽  
Vol 50 (2) ◽  
pp. 200-208 ◽  
Author(s):  
Simon Salager ◽  
Mathieu Nuth ◽  
Alessio Ferrari ◽  
Lyesse Laloui
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Water Retention ◽  
Void Ratio ◽  
Degree Of Saturation ◽  
Retention Data ◽  
Soil Water Retention ◽  
Retention Behaviour ◽  
Wide Range ◽  
Water Retention Behaviour

The paper presents an experimental and modelling approach for the soil-water retention behaviour of two deformable soils. The objective is to investigate the physical mechanisms that govern the soil-water retention properties and to propose a constitutive framework for the soil-water retention curve accounting for the initial state of compaction and deformability of soils. A granular soil and a clayey soil were subjected to drying over a wide range of suctions so that the residual state of saturation could be attained. Different initial densities were tested for each material. The soil-water retention curves (SWRCs) obtained are synthesized and compared in terms of water content, void ratio, and degree of saturation, and are expressed as a function of the total suction. The studies enable assessment of the effect of the past and present soil deformation on the shape of the curves. The void ratio exerts a clear influence on the air-entry value, revealing that the breakthrough of air into the pores of the soil is more arduous in denser states. In the plane of water content versus suction, the experimental results highlight the fact that from a certain value of suction, the retention curves corresponding to different densities of the same soil are convergent. The observed features of behaviour are conceptualized into a modelling framework expressing the evolution of the degree of saturation as a function of suction. The proposed retention model makes use of the theory of elastoplasticity and can thus be generalized into a hysteretic model applicable to drying–wetting cycles. The calibration of the model requires the experimental retention data for two initial void ratios. The prediction of tests for further ranges of void ratios proves to be accurate, which supports the adequacy of formulated concepts.

scholarly journals Modelling of soil-water retention curve considering the effects of existing salt solution in the pore fluid

2021 ◽  
Vol 337 ◽  
pp. 02001
Author(s):  
Hamed Sadeghi ◽  
Ali Golaghaei Darzi
Keyword(s):  
Soil Water ◽  
Osmotic Potential ◽  
Water Retention ◽  
Pore Fluid ◽  
Water Retention Curve ◽  
Model Parameters ◽  
Retention Data ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Retention Curve

Soil-water retention curve (SWRC) has a wide application in geoenvironmental engineering from the predication of unsaturated shear strength to transient two-phase flow and stability analyses. Although various SWRC models have been proposed to take into account some influencing factors, less attention has been given to consider the effects of pore fluid osmotic potential. Therefore, the key objective of this study is to extend van Genchten’s model so that osmotic potential is considered as an independent factor governing the SWRC behavior. The new model comprises only six variables, which can be calibrated through minimal experimental measurements. More importantly, most of the model parameters have physical meaning by correlating macroscopic volumetric behavior and general trends of SWRC to osmotic potential. The results of validation tests revealed that the new osmotic-dependent SWRC model can predict the retention data in terms of both total and matric suction for two different soils and various molar concentrations very good. The proposed modeling approach does not require any advanced mercury intrusion porosimetry (MIP) tests, yet it can deliver excellent predictions by calibrating only six parameters which are far less than those incorporated into similar models for saline water permeating through the pore structure.

scholarly journals Studying Unimodal, Bimodal, PDI and Bimodal-PDI Variants of Multiple Soil Water Retention Models: II. Evaluation of Parametric Pedotransfer Functions Against Direct Fits

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 896 ◽  
Author(s):  
Amir Haghverdi ◽  
Hasan Sabri Öztürk ◽  
Wolfgang Durner
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Water Retention ◽  
Organic Matter Content ◽  
Pedotransfer Functions ◽  
Model Parameters ◽  
Retention Data ◽  
Soil Water Retention ◽  
Data Set ◽  
Free Parameters

A high-resolution soil water retention data set (81 repacked soil samples with 7729 observations) measured by the HYPROP system was used to develop and evaluate the performance of regression parametric pedotransfer functions (PTFs). A total of sixteen soil hydraulic models were evaluated including five unimodal water retention expressions of Brooks and Corey (BC model), Fredlund and Xing (FX model), Kosugi (K model), van Genuchten with four free parameters (VG model) and van Genuchten with five free parameters (VGm model). In addition, eleven bimodal, Peters–Durner–Iden (PDI) and bimodal-PDI variants of the original expressions were studied. Six modeling scenarios (S1 to S6) were examined with different combinations of the following input predictors: soil texture (percentages of sand, silt and clay), soil bulk density, organic matter content, percent of stable aggregates and saturated water content (θs). Although a majority of the model parameters showed low correlations with basic soil properties, most of the parametric PTFs provided reasonable water content estimations. The VGm parametric PTF with an RMSE of 0.034 cm3 cm−3 was the best PTF when all input predictors were considered. When averaged across modeling scenarios, the PDI variant of the K model with an RMSE of 0.045 cm3 cm−3 showed the highest performance. The best performance of all models occurred at S6 when θs was considered as an additional input predictor. The second-best performance for 11 out of the 16 models belonged to S1 with soil textural components as the only inputs. Our results do not recommend the development of parametric PTFs using bimodal variants because of their poor performance, which is attributed to their high number of free parameters.

scholarly journals Parametric soil water retention models: a critical evaluation of expressions for the full moisture range

2018 ◽  
Vol 22 (2) ◽  
pp. 1193-1219 ◽  
Author(s):  
Raneem Madi ◽  
Gerrit Huibert de Rooij ◽  
Henrike Mielenz ◽  
Juliane Mai
Keyword(s):  
Hydraulic Conductivity ◽  
Soil Water ◽  
Water Retention ◽  
Minor Effect ◽  
Residual Water ◽  
Retention Data ◽  
General Criterion ◽  
Soil Water Retention ◽  
Retention Curve ◽  
Soil Hydraulic

Abstract. Few parametric expressions for the soil water retention curve are suitable for dry conditions. Furthermore, expressions for the soil hydraulic conductivity curves associated with parametric retention functions can behave unrealistically near saturation. We developed a general criterion for water retention parameterizations that ensures physically plausible conductivity curves. Only 3 of the 18 tested parameterizations met this criterion without restrictions on the parameters of a popular conductivity curve parameterization. A fourth required one parameter to be fixed. We estimated parameters by shuffled complex evolution (SCE) with the objective function tailored to various observation methods used to obtain retention curve data. We fitted the four parameterizations with physically plausible conductivities as well as the most widely used parameterization. The performance of the resulting 12 combinations of retention and conductivity curves was assessed in a numerical study with 751 days of semiarid atmospheric forcing applied to unvegetated, uniform, 1 m freely draining columns for four textures. Choosing different parameterizations had a minor effect on evaporation, but cumulative bottom fluxes varied by up to an order of magnitude between them. This highlights the need for a careful selection of the soil hydraulic parameterization that ideally does not only rely on goodness of fit to static soil water retention data but also on hydraulic conductivity measurements. Parameter fits for 21 soils showed that extrapolations into the dry range of the retention curve often became physically more realistic when the parameterization had a logarithmic dry branch, particularly in fine-textured soils where high residual water contents would otherwise be fitted.

scholarly journals Modelling Soil Water Retention Using Support Vector Machines with Genetic Algorithm Optimisation

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Krzysztof Lamorski ◽  
Cezary Sławiński ◽  
Felix Moreno ◽  
Gyöngyi Barna ◽  
Wojciech Skierucha ◽  
...  
Keyword(s):  
Genetic Algorithm ◽  
Support Vector Machines ◽  
Soil Water ◽  
Water Retention ◽  
Model Development ◽  
Water Retention Curve ◽  
Support Vector ◽  
Retention Data ◽  
Soil Water Retention ◽  
Vector Machines

This work presents point pedotransfer function (PTF) models of the soil water retention curve. The developed models allowed for estimation of the soil water content for the specified soil water potentials: –0.98, –3.10, –9.81, –31.02, –491.66, and –1554.78 kPa, based on the following soil characteristics: soil granulometric composition, total porosity, and bulk density. Support Vector Machines (SVM) methodology was used for model development. A new methodology for elaboration of retention function models is proposed. Alternative to previous attempts known from literature, theν-SVM method was used for model development and the results were compared with the formerly used theC-SVM method. For the purpose of models’ parameters search, genetic algorithms were used as an optimisation framework. A new form of the aim function used for models parameters search is proposed which allowed for development of models with better prediction capabilities. This new aim function avoids overestimation of models which is typically encountered when root mean squared error is used as an aim function. Elaborated models showed good agreement with measured soil water retention data. Achieved coefficients of determination values were in the range 0.67–0.92. Studies demonstrated usability ofν-SVM methodology together with genetic algorithm optimisation for retention modelling which gave better performing models than other tested approaches.

scholarly journals Performance of the Groenevelt and Grant Model for Fitting Soil Water Retention Data from Brazilian Soils

2019 ◽  
Vol 43 ◽  
Author(s):  
Robson André Armindo ◽  
Quirijn de Jong van Lier ◽  
Maria Eliza Turek ◽  
Aline Mari Huf dos Reis ◽  
Marina Luciana Abreu de Melo ◽  
...  
Keyword(s):  
Soil Water ◽  
Water Retention ◽  
Retention Data ◽  
Soil Water Retention ◽  
Brazilian Soils
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