Improved Prediction of Hydraulic Conductivity with Soil Water Retention
Curve that Accounts for Both Capillary and Adsorption Forces
Abstract
Hydraulic conductivity curves (HCCs) are important parameters in land
surface modeling. The general way for predicting HCC from soil water
retention curve (SWRC) requires an additional input of the saturated
hydraulic conductivity. The time-consuming in measurement and more
importantly, the macro-effect near saturation, however, often result in
difficulty and poor performance in predicting the conductivity. In this
study, we provided a physically based method for predicting the HCC
fully from SWRC requiring no additional parameters. This is achieved by
applying an estimated conductivity (from SWRC) in the dry range as new
matching point, in together with modifying the HCC model developed by
Wang et al. (2018) that accounts for both capillarity and adsorption
forces. Testing with a total of 159 soil samples yielded that the new
model significantly improved the predictions of HCC, with
R2 being 0.74 and root mean value being 0.84 cm
dā1, nearly double and half of the
value predicted with the input of the saturated hydraulic conductivity,
respectively. The abrupt drop near saturation of the HCC model that
provided by Wang et al. (2018) for soils with small n values
close to 1, a parameter in shaping the SWRC, was also overcome by
introducing a non-zero air-entry value.