Rainfall and soil moisture

To model a rainfall event, we need to define both the characteristics of the rainfall event and the initial soil moisture conditions.

In the model, the characteristics of a rainfall event are described by two grids:

• Total rainfall (mm) : total height of rain event
• Effective duration (min) : effective duration of the event, i.e. the duration during which the rainfall intensity is greater than 0 mm/h.

Note: the model is not dynamic. It is therefore not possible to study an event with variable rainfall intensity. The model is run at constant rainfall intensity.

Initial soil moisture at the start of modelling is described according to two grids:

• Imbibition rainfall height (mm) : initial loss before the onset of runoff; imbibition is a function of soil texture and structure, but also of initial soil moisture;
• Soil water storage capacity (mm) : maximum height of water equivalent to total filling of soil porosity; a function of soil thickness and porosity ;