The differential equations described are supplemented by the boundary conditions:

• Boundary condition 1st type: Specification of fixed concentrations (attribute 1KON): c = c*

• Boundary condition 2nd type: Specification of a diffusive-dispersive mass flow on the boundary. However, the (almost) exclusive practical application is to make the boundary impermeable to diffusion and dispersion, so that the following applies:

(N denotes the outward-pointing normal to the model edge).

The system of equations can only be solved if a boundary condition of the first type is defined at a minimum of at least one node

For a transient mass transport equation, initial conditions must be specified for the start time in the entire model area.

Initial condition: Initial concentration for the start time t₀ of the transient calculation (attribute AKON):

c(t₀) = c*₀

Input parameters