Salt and water transport in unsaturated soil for non-conservative systems

Abstract

An analytical solution is developed for one-dimensional salt and water transport in soil systems with a steady intake velocity. Both water and solutes are non-conservative in the sense that they are removed by plant roots. Additionally, the solute (or any water-transported entity) may be lost through a first order reaction. The unique feature of the solution is the coupling of unsaturated flow to solute uptake by the use of a “reflection coefficient” describing selective uptake by the roots. Hydrodynamic dispersion is included in the initial formulation, but is assumed negligible in actual calculations. Four numerical examples illustrate the utility of the solution. In the first example the effects of rooting pattern are shown for two different discretely-layered uptake functions. Example two shows results of changes in the magnitude of the first order reaction coefficient while in the third example, computations are made for differences in the reflection coefficient including changes with depth. The final comparison shows the effect of varying leaching coefficients.