Laboratory equipment and calculation procedure to rapidly determine hysteresis of some soil hydrophysical properties under nonsteady flow conditions

Sobczuk, H.; Plagge, Rudolf; Walczak, Ryszard; Roth, Christian

doi:10.1002/jpln.19921550214

Cited by 8 publications

(2 citation statements)

References 14 publications

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“…Therefore the retention curves of soils with heterogeneous pore systems should be directly fitted to measured data. Preferably, these measurements are obtained from a transient flow experiment by simultaneously measuring ½ and 0 in high resolution [e.g., Sobczuk et al, 1992]. The flow characteristics of the experiment can then be used to optimize the two conductivityrelated unknowns, Ks and r, by solving the inverse problem.…”

Section: The Almost Perfect Agreement Between Measured and Estimated mentioning

confidence: 99%

Hydraulic conductivity estimation for soils with heterogeneous pore structure

Durner¹

1994

Water Resources Research

936

825

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The hydraulic conductivity function, which is required to solve the Richards equation, is difficult to measure. Therefore prediction methods are frequently used where the shape of the conductivity function is estimated from the more easily measured water retention characteristic. Errors in conductivity estimations can arise either from an invalidity of the prediction model for a given soil, or from an incorrect description of the retention data. This second error source is particularly important for soils with heterogeneous pore systems that cannot be adequately described by the usually used retention functions. To describe the retention characteristics of such soils, a flexible θ(ψ) function was formed by superimposing unimodal retention curves of the van Genuchten (1980) type. By combining this retention model with the conductivity prediction model of Mualem (1976), conductivity estimations for soils with heterogeneous pore systems are obtained. Estimated conductivities by this model and the classical van Genuchten‐Mualem method can differ by orders of magnitude. Thus reported disagreements between measured and estimated conductivities may in some cases be due to an inadequate description of the retention data rather than due to a failure of the prediction model.

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Section: The Almost Perfect Agreement Between Measured and Estimated mentioning

confidence: 99%

Hydraulic conductivity estimation for soils with heterogeneous pore structure

Durner¹

1994

Water Resources Research

936

825

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“…2).Water conductivity in an unsaturated zone was determined using a laboratory TDR (Time Domain Reflectometry) test measuring moisture, soil water potential, temperature and salinity using the instantaneous profile method (IPM) (Sławiński, 2003;Sławiński et al, 2002Sławiński et al, , 2006Sobczuk et al, 1992). Water conductivity was measured within the range from -0.1 to -100 kJ m -3, which is limited by the tensiometer measurement range.…”

Section: Methodsmentioning

confidence: 99%

Water conductivity of arctic zone soils (Spitsbergen)

Witkowska-Walczak¹,

Sławiński²,

Bartmiński³

et al. 2014

International Agrophysics

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A b s t r a c t. The water conductivity of arctic zone soils derived in different micro-relief forms was determined. The greatest water conductivity at the 0-5 cm depth for the higher values of water potentials (> -7 kJ m -3 ) was shown by tundra polygons (Brunic-Turbic Cryosol, Arenic) -904-0.09 cm day -1 , whereas the lowest were exhibited by Turbic Cryosols -95-0.05 cm day -1 . Between -16 and -100 kJ m -3 , the water conductivity for tundra polygons rapidly decreased to 0.0001 cm day -1 , whereas their decrease for the other forms was much lower and in consequence the values were 0.007, 0.04, and 0.01 cm day -1 for the mud boils (Turbic Cryosol (Siltic, Skeletic)), cell forms (Turbic Cryosol (Siltic, Skeletic)), and sorted circles (Turbic Cryosol (Skeletic)), respectively. In the 10-15 cm layer, the shape of water conductivity curves for the higher values of water potentials is nearly the same as for the upper layer. Similarly, the water conductivity is the highest -0.2 cm day -1 for tundra polygons. For the lower water potentials, the differences in water conductivity increase to the decrease of soil water potential. At the lowest potential the water conductivity is the highest for sorted circles -0.02 cm day -1 and the lowest in tundra polygons -0.00002 cm day -1 .

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