Analysis of salinity profiles in lateritic soils of south-western Australia

Salinity profiles in deeply weathered lateritic soils of south-western Australia frequently exhibit very high concentrations in the unsaturated zone above a less saline water table. A one-dimensional steady-state model using the simultaneous mass balance equations for water and solute is used to predict salt profiles which are compared with those observed. The model assumes input of salt in rainfall and water uptake by plants. Model parameters imply magnitudes of transpiration, water flux rates and possible mechanisms for water movement to the saturated zone. Some salt profiles cannot be accounted for with the steady-state model. In some cases there appears to be an injection of low salinity water at depth which could occur by movement through preferred pathways from the soil surface. In other cases the probable explanation is that the profiles are accumulating salts under the present hydrologic regime.