A Two‐Phase Numerical Model for Prediction of Infiltration: Case of an Impervious Bottom

Abstract

A numerical procedure to describe soil moisture evolution in a column with an impervious bottom for varied boundary conditions at the soil surface is presented. The procedure accounts for viscous resistance to simultaneous flow of water and air and for air compression. The method was programmed for the computer. In one case study a 10‐cm‐deep soil column is subjected to a steady rainfall at the surface. Moisture profiles and infiltration rates are calculated by both the one‐ and two‐phase approaches. Comparison demonstrates the magnitude of the error incurred when air effects are not incorporated in the analysis. In a second case study a 100‐cm‐deep soil column is subjected to a sequence of two different rainfall rates. Again comparison of results by the two approaches (traditional versus two phase) provides a measure of the error resulting from the neglect of air effects in the analysis. Not only is capacity infiltration rate greatly reduced after ponding of soil surface but the ponding times themselves are greatly reduced due to increased viscous resistance to flow when airflow is considered in the analysis. The more rigorous analysis complicates little the basic numerical procedures and performs the calculations at essentially no extra cost.