Predicting saturated and unsaturated hydraulic conductivity in undisturbed soils from soil water characteristics

Poulsen, T.G.; Moldrup, P.; Yamaguchi, T.; Jacobsen, O.H.

Soil Science 164(12): 877-887


ISSN/ISBN: 0038-075X
Accession: 003530974

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A new model for predicting saturated hydraulic conductivity (Ks) in undisturbed soils from macroporosity ( epsilon 100), defined as the air-filled porosity at a soil-water potential of( psi =-100 cm H2O), was developed using data for 23 undisturbed soils (90 horizons). The new Ks model compared well with measurements when tested against independent datasets for 73 undisturbed soils (191 horizons) from the UNSODA database and gave improved predictions (accuracy within one order of magnitude) compared with existing Ks models. Two new models for predicting relative hydraulic conductivity (K/Ks) in relatively moist, ( psi >-350 cm H2O) undisturbed soils from soil-water content ( theta ) and the Campbell soil-water retention parameter, b, were developed using conductivity and water retention data for the 73 soils from UNSODA. The new K/Ks models represent modifications of the recently presented DLC and SLC models for predicting K/Ks in sieved, repacked soils. The modified DLC and SLC models were combined with the new Ks model, yielding new two-parameter ( epsilon 100, b) models for unsaturated hydraulic conductivity (K( theta )) in undisturbed soil. The two new K( theta ) models were successfully tested against independent K( theta ) data. The classical Campbell [See Soil Science (1974) 117, 311-314] K/Ks model, combined with the new, more accurate Ks model, gave K( theta ) prediction accuracy almost as good as the modified DLC and SLC K( theta ) models. The suggested two-parameter K( theta ) models require knowledge of only the soil-water retention curve, including a measurement at Psi =-100 cm H2O, and seem promising for use in deterministic and stochastic models for water transport in natural, undisturbed soils.