Effect of soil water hysteresis on solute movement during intermittent leaching

The use of a computer‐based numerical solution of the hydrodynamic dispersion equation, coupled with a program for the movement of soil water incorporating an interpolative hysteresis model, is described. Results are presented for nonreactive solute movement during an intermittent leaching regime under a constant concentration boundary condition at the surface, both including and excluding the effects of soil water hysteresis. When hysteresis data is included in the analysis, the solute mass profiles indicate that the solute moves through the soil profile in a series of well‐defined peaks. This is in marked contrast to the situation in which hysteresis is neglected. For this case the well‐defined peaks disappear after the first infiltration event, and the solute becomes fairly uniformly distributed much deeper in the profile. The possible application of intermittent leaching is discussed briefly.