Integrated modelling of the soil–water–atmosphere–plant system using the model SWAP 2·0 an overview of theory and an application

The vadose zone plays an essential role in all types of processes that occur in the soil. Modelling of the processes in the vadose zone helps to understand and quantify effects of, for example, land use, irrigation, salinity and climate changes. Version 2 of SWAP (soil-water-atmosphere-plant) is a numerical model that simulates the (interaction between) one-dimensional soil moisture, heat and solute transport in the topsoil layers. The influence of all these processes on crop growth may be simulated as well. This article describes briefly some of the options the program offers. The results of a sensitivity analysis are discussed, followed by a case study on variations in soil salinity in a coastal area