WAVES

The interactions between climate, vegetation and soil are all around us. They provide the driving forces and fluxes for the atmosphere above the ground, and the large groundwater systems below it. Understanding and quantifying these interactions has therefore long been of great interest to researchers.

In the Australian context, the main questions are what is the current water balance, how has it changed from historical levels, and what is the optimum land management regime to satisfy a range of competing needs? Dryland salinity is a good example of a disturbed water balance with land management implications. Historically groundwater levels were well below the soil surface, and were kept there by deep-rooted perennial native vegetation. Widespread clearing of this vegetation, and replacement with more shallow-rooted annual cropping and grazing systems, has led to an increase in groundwater recharge. This has caused groundwater levels to rise, mobilise the stored salt in the soil profile, and bring it close to the surface where evaporative concentration has resulted in dryland salinity. The question being addressed in this field is whether rising water level trends can be halted or reversed using only vegetation management, or in combination with engineering options.

WAVES is a one-dimensional daily-timestep model that simulates the fluxes of mass and energy between the atmosphere, vegetation, and soil systems, which has been under development since 1993. It is a process-based model that couples these systems by modelling the interactions and feedbacks between them. WAVES attempts to model each sub-system with a consistent level of detail, so that no area is over emphasized or requires too many parameters, and similarly no area is treated in a trivial manner. More than this, WAVES tries to strike a balance between the complexity of the model as a whole, the usefulness of the model and its ease of use, and the accuracy of the model outputs. If these balances have been struck, then WAVES should be easy enough to use, but accurate enough to believe.

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