Estimation of the Saturated Hydraulic Conductivity in Clay Soils from Soil Moisture Retention Data

A generalized Kozeny-Carman equation was employed to relate saturated hydraulic conductivity (Ks) to effective porosity (φe) in clay profiles in Sweden with clay content >15% were analyzed. The value empirical constants. The term φe was defined as porosity (φ) minus soil-water content at −30 kPa. Around 500 horizons from 60 soil profiles in Sweden with clay content >15% were analyzed. The value of n was tested with two statistical methods. According to the first method, a regression test on the log-log relationship between Ks and φe with least-squares lines fitted through the data, the exponent n was found to lie around 2 for soils with high clay content (>40%), and 3 for soils with lower clay content (15–40%). The correlation coefficients were moderate, ranging from 0.51 to 0.71 for different clay soil groups. In the second method, the cumulative frequency distributions of scaling factors for Ks determined from measured values of Ks were compared with scaling factors for Ks determined from φe. Reasonable agreements were obtained with n = 4 to 5 for soils with clay content >40%, and with n = 5 to 6 for soils with clay content 15 to 40%. The second method gave n-values that correspond well with other recent published work. The results indicate that the spatial distribution of Ks is estimated reasonably well from φe values, whereas the individual values of Ks are not estimated as well.