During the past 10 years, the simulation model SWAP (Soil, Water, Atmosphere, Plant) was developed by the Sub-Department Water Resources of Wageningen University jointly with the Department Water and Environment of Alterra Green World Research. SWAP simulates vertical transport of water, solutes and heat in variably saturated, cultivated soils at field scale level and during whole growing seasons. Different versions of the model have been applied worldwide in research, education and as a decision support tool in the management of agricultural, horticultural and natural systems water flow in homogeneous and heterogeneous soils with or without the influence of groundwater. The main features of and theoretical concepts behind SWAP are described, in particular soil water flow, solute transport and crop growth
