ESTIMATION OF THE SOIL-WATER SORPTIVITY FROM INFILTRATION IN VERTICAL SOIL COLUMNS

This paper presents a simple method for estimating the soil-water sorptivity (S) from vertical infiltration experiments at ponding conditions. The proposed estimation method is based on the Haverkamp et al. (R. Haverkamp, J.-Y. Parlange, J. L. Starr, G. Schmitz, and C. Fuentes. 1990. Infiltration under ponded conditions. 3. A predictive equation based on physical parameters. Soil Sci. 149:292–300.) predictive infiltration equation. This equation is simplified, so that a simple analytical solution is obtained for the sorptivity. The new S estimation method requires measurement of cumulative infiltration versus time and independent measurement of the saturated hydraulic conductivity on the same soil cores as used for the infiltration experiment. Criteria for avoiding numerical instability when using the new estimation method are given. Use of the proposed method is illustrated on infiltration data measured on undisturbed sand cores. The method gave good and robust estimates of the soil-water sorptivity (coefficient of variation > 25% for all S estimates). Horizontal and vertical infiltration tests for homogeneous packed soil columns showed good agreement between the new S estimation method and the classical Philip method for horizontal infiltration at nonponding conditions.