Reevaluation of the Evaporation Method for Determining Hydraulic Functions in Unsaturated Soils

Wendroth, Ole; Ehlers, W.; Hopmans, Jan W.; Kage, Henning; Halbertsma, J.

doi:10.2136/sssaj1993.03615995005700060007x

Cited by 153 publications

(103 citation statements)

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“…The samples were collected at the same depth than for K s determination and with similar number of replicates. They were saturated in the same way than for K s determination (Wendroth et al, 1993 andTamari et al, 1993). The mathematical procedures used to calculate K from Darcy's law, and the procedure used to fit Van Genuchten (1980) model are described in the work of Mohrath et al (1997).…”

Section: Sampling and Methodsmentioning

confidence: 99%

Change in the hydraulic properties of a Brazilian clay Ferralsol on clearing for pasture

Balbino¹,

Bruand²,

Cousin³

et al. 2004

Geoderma

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Ferralsols under native vegetation have a weak to moderate macrostructure and a welldeveloped microstructure corresponding to subrounded microaggregates that are usually 80 to 300 μm in size. The aim of this study was to analyze how the hydraulic properties of a clay Ferralsol were affected by a change of structure when the native vegetation is cleared for pasture. We studied the macrostructure in the field and microstructure in scanning electron microscopy. The water retention properties were determined by using pressure cell equipment. We determined the saturated hydraulic conductivity, K s , by applying a constant hydraulic head to saturated core samples, and the unsaturated hydraulic conductivity, K(Ψ), by applying the evaporation method to undisturbed core samples. Results showed a significant decrease in the water retained at −1 and −10 hPa from 0-to 40-cm-depth when the native vegetation is cleared for pasture. That decrease in the water retained was related to a smaller development of microaggregation and greater proportion of microaggregates in close packing. For smaller water potential, there was no difference of water retained at every depth between native vegetation and pasture. Pedotransfer functions established earlier for Brazilian Ferralsols and using clay content as single predictor gave pretty good results but the precision of the estimation decreased when the water potential increased. This decrease in the precision was related to the lack of predictor taking structure into account. K s and K(Ψ) showed an upward trend with depth under native vegetation and pasture. Except at 0-7-cm depth between the Brachiaria clumps in the pasture where smaller K s and K(Ψ) than at the other depth was recorded whatever land use, we did not record any significant difference of K s and K(Ψ) at every depth between native vegetation and pasture. The upward trend shown by the hydraulic conductivity with depth was related to the increase in the development of microaggregation with depth.

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Section: Sampling and Methodsmentioning

confidence: 99%

Change in the hydraulic properties of a Brazilian clay Ferralsol on clearing for pasture

Balbino¹,

Bruand²,

Cousin³

et al. 2004

Geoderma

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“…The difference between the f min values of the best and the worst fit is for soils 4 to 6 about one to two orders of magnitude ( Table 2). Note that the evaporation experiment comprises no information about conductivity close to saturation, as pointed out by Tamari et al [1993], Wendroth et al [1993], and Peters and Durner [2008]. The best-fit parameters of all seven soils are listed in Table 4.…”

Section: Coupled Estimation Of Q(h) and K(h)mentioning

confidence: 99%

A simple model for describing hydraulic conductivity in unsaturated porous media accounting for film and capillary flow

Peters

Durner

2008

Water Resources Research

118

150

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[1] The commonly used models for characterizing hydraulic conductivity of porous media rely on pore bundle concepts that account for capillary flow only and neglect film flow. Experimental evidence suggests that water flow at medium to low water contents in unsaturated porous media can be significantly underestimated by these capillary bundle models. We present a new model that combines a simple film flow function with the capillary flow model of Mualem. This new model can easily be coupled to any water retention function. Moreover, due to its mathematical simplicity, it can easily and efficiently be implemented in existing codes for the numerical solution of unsaturated flow problems. We investigated a set of soil water retention and conductivity data from the literature that all reached dry conditions and were poorly described by existing capillary bundle models. These data were well described with the new model if the model was coupled with an appropriate retention function. Investigation of conductivity data from the UNsaturated SOil hydraulic DAtabase (UNSODA) database showed that, in 75% of all data sets, the new model achieved the best performance using a modified version of Akaike's information criterion. The numeric simulation of an evaporation scenario using Richards's equation showed that by neglecting film flow, the evaporation rate may be underestimated by more than an order of magnitude.Citation: Peters, A., and W. Durner (2008), A simple model for describing hydraulic conductivity in unsaturated porous media accounting for film and capillary flow, Water Resour. Res., 44, W11417,

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“…These cores were used to determine (desorption) water retention curves, the unsaturated hydraulic conductivities and bulk densities. The unsaturated soil hydraulic properties were determined in the lab during transient conditions using the evaporation method (Wendroth et al, 1993) and during steady-state conditions using the hanging water column method and a pressure apparatus (Dane and Topp 2002). Hydraulic conductivities were calculated using the approach of Wind (1968).…”

Section: Lab Measurementsmentioning

confidence: 99%

Land-use effects on flood generation – considering soil hydraulic measurements in modelling

et al. 2009

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Abstract. The investigation in the catchment of the Mulde (51 • 0 55 N, 13 • 15 54 E Saxony, Germany) researches the effect of afforestation measures on the soil hydraulic properties. The concept of a "false chronosequence" was used to quantify the time-dependent dynamical character of the forest impact. Four adjacent plots were identified at a test location with comparable pedological start conditions and a set of tree stands of different age: (1) arable field (initial state); (2) 6-year-old afforestation; (3) 50-year-old afforestation; (4) ancient natural forest ("target" stocking). Water retention curves and unsaturated conductivities were analysed in the lab. In the field, the undisturbed infiltration capacities were measured quantitatively (hood infiltrometer) and qualitatively (brilliant blue tracer). Pronounced differences between all 4 plots were detected. The afforestation causes an increased infiltration and soil water retention potential. Especially the topsoil layers showed a distinct increase in conductivity and portion of coarse/middle pores. The influence of these changes on rainfall-runoff calculations at the test location was analysed in this study.

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Reevaluation of the Evaporation Method for Determining Hydraulic Functions in Unsaturated Soils

Cited by 153 publications

References 0 publications

Change in the hydraulic properties of a Brazilian clay Ferralsol on clearing for pasture

Change in the hydraulic properties of a Brazilian clay Ferralsol on clearing for pasture

A simple model for describing hydraulic conductivity in unsaturated porous media accounting for film and capillary flow

Land-use effects on flood generation – considering soil hydraulic measurements in modelling

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