Predicting Infiltration for Shallow Water Table Soils with Different Surface Covers

ABSTRACT TWO approximate methods were used to predict infiltration for shallow water table conditions. The method proposed by Bouwer (1969) was modified so that it would predict saturated flow through the column after the water table rose to the surface; air pressure ahead of the wetting front was not considered in this method. The second method which did consider the air impedance, was a three-stage model based on the work of Adrian and Franzini (1966). Results of these two prediction models were compared with experimental infiltration measurements on soil columns with three different surface conditions: fallow or bare, soybean, and fescue grass. Comparisons were made at different stages of the crop production cycle. Results showed that the three-stage model gave better predictions than the modified Bouwer's model for the conditions considered in this study. When original saturated hydraulic conductivity values were used, all prediction models underestimated infiltration for profiles with grass surface cover and overestimated infiltration for profiles without a surface cover. Much better predictions were obtained when hydraulic conductivities were measured after the crop had been established or, in the case of bare profiles, after the surface had been weathered or disturbed.