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SWIM is an acronym that stands for Soil Water Infiltration and Movement. It is a software package developed within the CSIRO Land and Water for simulating infiltration, evapotranspiration, and redistribution. The first version (SWIMv1) was published in 1990 (Ross, 1990b). Version 2 of the model (identified as SWIMv2.0), which combines water movement with transient solute transport and which accommodates a variety of soil property descriptions and more flexible boundary conditions, was completed in 1992.

SWIM v2.0 is based on a numerical solution of the Richards' equation and the advection-dispersion equation. It can be used to simulate runoff, infiltration, redistribution, solute transport and redistribution of solutes, plant uptake and transpiration, soil evaporation, deep drainage and leaching. Soil water and solute transport properties, initial conditions, and time dependent boundary conditions (e.g., precipitation, evaporative demand, solute input) need to be supplied by the user in order to run the model.

Major Features include the ability to deal with:

  • layered and gradational soils such as occur in field soils where hydraulic properties vary with depth down the profile, either abruptly or gradually,
  • saturated/unsaturated conditions as can occur at layer interfaces, which result in locally perched water,
  • surface ponding as can occur under high rainfall intensities,
  • surface runoff, where 'excess' water can be removed from the system,
  • surface sealing, where the properties of the surface may vary directly as a function of rainfall energy, and hence as a function of time,
  • rainfall dynamics, so that real storm intensities (down to 1-minute resolution and below) can be simulated,
  • solute transport,
  • flexible description of hydraulic properties and boundary conditions
  • vapour flow, hysteresis, bypass flow, osmotic effects, and potential subsurface downslope flow,
  • specifications of root length density with depth and time, and potential plant water uptake with time,
  • allows for 'cultivations' or 'disturbances' of the soil surface which enable the application of dry fertiliser (solute) and resetting of the surface conductance and surface roughness values at specified times.

The overall purpose of the model is to address issues relating to the soil water and solute balance. As such it is a research tool that can be integrated in laboratory and field studies concerned with soil water and solute transport. It is also eminently suitable for management and education.

For further information Email Dr Keith Bristow  or Telephone (07) 4753 8596