The vertical movement water in stratified porous material: 1. Infiltration

The infiltration law of Green and Ampt has long been established as an adequate approximation in uniform soil profiles. It is here extended to include heterogeneous profiles. Formulas are developed to express three relationships. Firstly, the infiltration law is derived for a profile consisting of a succession of n different layers with conductivity decreasing from the surface. Secondly, an expression is derived for the conductivity profile that will give a specified infiltration law, and in particular a linear infiltration law with specified parameters. Thirdly, this expression serves to determine the conductivity when the infiltration law is observed. Experiments are described to measure the infiltration rates into layered columns or porous material, the results of which confirm the theory.