Scaling Parameters of the Lewis-Kostiakov Water Infiltration Equation Across Soil Textural Classes and Extension to Rain Infiltration

Authors: Ahuja, Lajpat; Kozak, Joseph; Andales, Allan; Ma, Liwang

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2007
Publication Date: 8/24/2007
Citation: Ahuja, L.R., Kozak, J.A., Andales, A.A., Ma, L. 2006. Scaling Parameters of the Lewis-Kostiakov Water Infiltration Equation Across Soil Textural Classes and Extension to Rain Infiltration. Transactions of the ASABE. Vol.50(5): 1525-1541.2007.

Interpretive Summary: A recent study showed that the Brooks-Corey equation parameters for soil hydraulic properties were strongly correlated to the pore-size distribution index (lambda), the slope of the log-log soil moisture characteristic curve across eleven soil textural classes from sand to clay. It further showed that lambda’s related and scaled cumulative infiltration across textural classes under different rainfall and initial conditions using normalization of the Green-Ampt equation and empirical relations. The objectives herein were to explore if establishing more compact scaling could be achieved through relationships between the parameters of the empirical Lewis-Kostiakov infiltration equation and lambda or the effective saturated hydraulic conductivity Ks across different soil types for instantaneous ponding cases. The Root Zone Water Quality Model simulated instantaneous ponding at two initial pressure heads (-1500 and -100 kfa) using the detailed hydraulic parameters for each soil. The two Kostiakov parameters (alpha, k) were shown to have fairly strong explicit relationships with lambda ( r2 =0.78-0.88) and stronger with Ks (r2=0.94-0.99). Additionally, alpha was essentially the same for the two initial pressure heads. The intercept k varied with the pressure head condition but was related to the initial soil water deficit in the same way as sorptivity. Upper time limits for applicability of Lewis-Kostiakov equation (t b) were also more strongly related to Ks (r2 = 0.99). Finally, infiltration at times >t b estimated from alpha, k, and Ks agreed very well with the simulated data (RMSE=0.041-0.59). These empirical relations of Kostiakov (Lewis) equation parameters with lambda or Ks for intermediate soils can be used to approximate parameters and infiltration for other soils and conditions by interpolation, and provide a basis for estimating spatial variability of infiltration and soil water on the landscape.

Technical Abstract: A recent study showed that the Brooks-Corey equation parameters for soil hydraulic properties were strongly correlated to the pore-size distribution index (lambda), the slope of the log-log soil moisture characteristic curve across eleven soil textural classes from sand to clay. It further showed that lambda’s related and scaled cumulative infiltration across textural classes under different rainfall and initial conditions using normalization of the Green-Ampt equation and empirical relations. The objectives herein were to explore if establishing more compact scaling could be achieved through relationships between the parameters of the empirical Lewis-Kostiakov infiltration equation and lambda or the effective saturated hydraulic conductivity Ks across different soil types for instantaneous ponding cases. The Root Zone Water Quality Model simulated instantaneous ponding at two initial pressure heads (-1500 and -100 kfa) using the detailed hydraulic parameters for each soil. The two Kostiakov parameters (alpha, k) were shown to have fairly strong explicit relationships with lambda (r2 =0.78-0.88) and stronger with Ks (r2=0.94-0.99). Additionally, alpha was essentially the same for the two initial pressure heads. The intercept k varied with the pressure head condition but was related to the initial soil water deficit in the same way as sorptivity. Upper time limits for applicability of Lewis-Kostiakov equation (t b) were also more strongly related to Ks (r2 = 0.99). Finally, infiltration at times >t b estimated from alpha, k, and Ks agreed very well with the simulated data (RMSE=0.041-0.59). These empirical relations of Kostiakov (Lewis) equation parameters with lambda or Ks for intermediate soils can be used to approximate parameters and infiltration for other soils and conditions by interpolation, and provide a basis for estimating spatial variability of infiltration and soil water on the landscape.