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Three-region Campbell Model for Unsaturated Hydraulic Conductivity in Undisturbed Soils

^a Dept. of Environmental Engineering, Institute of Life Sciences, Aalborg University, Sohngaardsholmsvej 57, DK-9000 Aalborg, Denmark
^b Danish Institute of Agricultural Sciences, Dept. of Crop Physiology and Soil Science, Research Centre Foulum, P.O. Box 50, DK-8830 Tjele, Denmark

View larger version (19K): [in a new window]   Fig. 1. Three-region Campbell (TRC) model concept, (a) soil water retention and (b) hydraulic conductivity as a function of soil-water content. Data from UNSODA (Leij et al., 1996) Soil 4032.

View larger version (29K): [in a new window]   Fig. 2. Relation between the Campbell soil-water retention parameters (b2, b3) and the TRC hydraulic conductivity parameters (ß2, ß3) in the mesopore and micropore regions.

View larger version (18K): [in a new window]   Fig. 3. Relation between soil-water retention parameters b2 and b3 for 100 soils from UNSODA. Dotted lines indicate 95% prediction intervals.

View larger version (50K): [in a new window]   Fig. 4. Soil water retention, hydraulic conductivity, and predicted hydraulic conductivity by the Campbell (1974) model with b = b2, the Van Genuchten (1980) model using (KS, S), the Van Genuchten (1980) model using (KS = K2, S = 2), and the TRC model. Data for four undisturbed, structured soils from UNSODA.

View larger version (25K): [in a new window]   Fig. 5. Relative deviation between measured and predicted LogK as a function of scaled water content ( - min)/(s - min) where min is the smallest for which LogK is measured in Fig. 4.

View larger version (32K): [in a new window]   Fig. 6. Soil water retention, hydraulic conductivity, and predicted hydraulic conductivity by the Campbell (1974) model with b = b2, the van Genuchten (1980) model using (KS, S), the Van Genuchten (1980) model using (KS = K2, S = 2), and the TRC model. Data for two undisturbed, non-structured soils from UNSODA.

View larger version (35K): [in a new window]   Fig. 7. Measured and predicted values of hydraulic conductivity for 100 soils from UNSODA using the Campbell (1974) model with b = b2, and the TRC model for sandy soils, loamy and clayey soils and all soils combined.

View larger version (27K): [in a new window]   Fig. 8. Three soils from UNSODA where Region II starts at a soil-water matric head significantly below -10 cm H2O causing over-prediction of unsaturated hydraulic conductivity by the TRC model.

View larger version (26K): [in a new window]   Fig. 9. Soil water retention, hydraulic conductivity, and predicted hydraulic conductivity by the TRC model for three selected sampling locations in three undisturbed Danish soils from (data from Lindhardt et al., 2002).

View larger version (28K): [in a new window]   Fig. 10. Measured and predicted values of hydraulic conductivity by the TRC model, for three undisturbed Danish soils (data from Lindhardt et al., 2002). Dotted lines are 95% prediction interval.