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Media type:
E-Article
Title:
Prediction of the absolute hydraulic conductivity function from soil water retention data
Contributor:
Peters, Andre;
Hohenbrink, Tobias L.;
Iden, Sascha C.;
van Genuchten, Martinus Th.;
Durner, Wolfgang
Published:
Copernicus GmbH, 2023
Published in:
Hydrology and Earth System Sciences, 27 (2023) 7, Seite 1565-1582
Language:
English
DOI:
10.5194/hess-27-1565-2023
ISSN:
1607-7938
Origination:
Footnote:
Description:
Abstract. For modeling flow and transport processes in the soil–plant–atmosphere system, knowledge of the unsaturated hydraulic properties in functional form is mandatory. While much data are available for the water retention function, the hydraulic conductivity function often needs to be predicted. The classical approach is to predict the relative conductivity from the retention function and scale it with the measured saturated conductivity, Ks. In this paper we highlight the shortcomings of this approach, namely, that measured Ks values are often highly uncertain and biased, resulting in poor predictions of the unsaturatedconductivity function. We propose to reformulate the unsaturated hydraulic conductivity function by replacing the soil-specific Ks as a scaling factor with a generally applicable effective saturated tortuosity parameter τs and predicting total conductivity using only the water retention curve. Using four different unimodal expressions for the water retention curve, a soil-independent general value for τs was derived by fitting the new formulation to 12 data sets containing the relevant information. τs was found to be approximately 0.1. Testing of the new prediction scheme with independent data showed a meanerror between the fully predicted conductivity functions and measured dataof less than half an order of magnitude. The new scheme can be used wheninsufficient or no conductivity data are available. The model also helps topredict the saturated conductivity of the soil matrix alone and thus todistinguish between the macropore conductivity and the soil matrixconductivity.