An analytical solution for predicting solute transport during ponded infiltration

An analytical solution is presented for one-dimensional solute transport in soil during ponded infiltration. The pore-water velocity v = q/ theta in the convection-dispersion transport equation was obtained by assuming that the water flux density q in the soil can be calculated with the Green-Ampt infiltration model, q = a + b/I, in which a and b are constants and I is the cumulative infiltration rate evaluated using Philip's two-term infiltration equation. The water content theta was approximated by the saturated water content, theta sub(s). Through an appropriate transformation, the solute transport equation for transient unsaturated flow conditions was linearized and solved analytically for a general initial concentration profile given by an arbitrary number of straight line segments. The solution compared well with more complete numerical solutions of the transport problem, as well as with several experimental data sets.