...
The Irrigator demand model is based on the existing demand models, including the NOW IQQM Crop Model 2, Victorian Pride Model and the FAO crop water use guidelines (FAO-56FAO56). The strengths from each of these demand models have been extracted and included into the Irrigator demand model. In addition, new functional requirements identified by NSW NOW reviews and Victorian studies have been included.
...
The soil water balance for each crop is modelled using a single layer moisture store (Equation 1), as outlined in FAO 56 FAO56 – Chapter 8. Equation 85 from FAO56 represents the water balance of the rootzone.
...
Crop evapotranspiration is calculated using the single crop coefficient approach described in FAO-56 FAO56 (Equation 6). For further information on how this approach is implemented in Source see Crop coefficients at various growth stages can be modelled in Source as described in the Irrigation Demand Model Crop Factors SRG entry. Alternatively, Source also offers sufficient flexibility to apply daily crop factors if they are known for a particular crop based on a different source or method.
The effects of soil water stress on crop ET are calculated by multiplying the crop coefficient by the water stress coefficient (Ks). The Ks value is evaluated based on soil water depletion at the start of the time-step.
...
Effective rain considers that a proportion of rainfall will be interception or lost and not infiltrate. FAO-56 FAO56 proposes an interception loss of 0.2 * ETo. This interception loss is included into Irrigation to define effective rain as described in (Equation 7).
...