Solute transport modelling in soil for irrigation field experiments with alkali water

To assess the effects of alkali water use for irrigation on soil and ground water quality, experiments have been conducted. These experiments indicate how the soil solution concentrations and cation exchange complex composition change under the influence of irrigation water composition. To understand the complicated chemical processes that affect the solute transport through soil, numerical simulations have been done. The simulated solution and exchange complex compositions were compared with the results of the experiments that were performed in the field. The comparisons show a good agreement. This suggests that the dominant processes that were accounted for in the numerical simulations have been adequately identified. To investigate whether this is indeed the case, even simpler analytical solutions have been used for comparison with both the experimental and numerical results. These analytical solutions require that the concentration fronts for different cations can be decoupled. The analytical solutions describe the observations in the experiments well and support that the major processes have been identified and that model parameter values are appropriate. These results may be useful to assess long term effects of alkali water use and sodic soil reclamation.