For the calculation of the direct problem control parameters must be defined during the inverse modelling. Here are some limitations to be considered:

 

Generally, a coupled flow and transport model can be calculated. Dispersivities and other model data only required for the transport are currently not optimized and measured concentrations are not included as observation data. Therefore, the transport calculation is currently not scheduled in an inverse modelling. An exception is the optimization of flow parameters for a density-dependent model. In this case, the transport problem must be calculated as well.

In general, it is possible in a transient calculation, to save the calculated potentials for certain time steps or time series of individual nodes in order to reduce the required storage space. In the inverse modelling, however, the potential heads are needed for each time step of the transient calculation. Therefore the potential heads must be stored for all time steps in a transient inverse modelling.

The continuation of a transient calculation (a “warmstart”) with the null-file is in an inverse modelling calculation not possible. Thus, storing the data of the transient calculation for a continuation of the iteration (out66-file) does not make sense.

In a transient three-dimensional or vertical flow model, which is calculated saturated/unsaturated, the relative K-values can be calculated iteratively within a time step. This is in an inverse modelling not possible. When such problems occur it must be worked with an update of the relative K-values from one time step to the next (i.e. only one iteration per time step and without attenuating the iteration: attenuation factor = ca. 1.0).

As a further limitation with respect to a normal flow calculation the inverse modelling does not work with minimum or maximum in- or exfiltration rates (MXKI, MXKE, MXEI, MXEE). To keep leakage rates still in a certain size, the observation data LKNO can be used.