A Limiting Flux Condition in Infiltration into Heterogeneous Porous Media

Infiltration into a porous medium in which the hydraulic conductivity increases with depth is shown to approach at quite early times a limiting flux condition. This condition is defined by a pressure head profile in the saturated zone becoming tangential to the water entry value profile. Equations are presented enabling the values of the limiting flux ( f l ) and the elevation of the point of contact ( z l ) to be calculated in terms of the material properties and the boundary conditions. Below z l an unsaturated zone exists and wetting up in this zone continues under the condition of limiting flux. A method is presented whereby the pressure and water content profiles for this zone can be determined.