# HydroGeoSphere/Transport Conditions (Initial)

It should be noted that the instructions given here affect the behaviour of one or more solutes, which should already have been defined according to the instructions given in Section 5.6.3.1.
Currently the initial condition (for both mobile and immobile zones if dual porosity) defaults to 0.0 unless one of the following instructions are included.

## Initial concentration

* bc_val(i), i=1,nspeciesmob Initial concentration [M L$^{−3}$] for each solute.
Chosen nodes in the currently active media (see Section 5.8.1) are assigned an initial concentration value.

## Initial concentration from output file

* fname Name of the file which contains the initial concentration data.
All nodes in the currently active media (see Section 5.8.1) are assigned an initial concentration value which is read from a previously generated output file with a name of the style prefixo.concentration.suffix, where suffix is a 3-digit number identifying the output file. Since it is applied to the current media type you can use, for example, prefixo.concentration.003 for the porous media and prefixo.concentration_overland.003 for the surface domain. This can be useful, for example, when a run crashes (since you don’t have to start simulation from scratch).

## Initial immobile concentration from output file

* fname Name of the file which contains the initial immobile zone concentration data.
As above for the instruction Initial concentration from output file except immobile zone initial concentrations are assigned. This insures that the mobile and immobile zones will be in equilibrium at the start of a simulation if the same file concentration output file is used to define the initial conditions.

## Initial concentration from file

* fname Name of the file which contains the initial concentration data.
All nodes in the currently active media (see Section 5.8.1) are assigned an initial concentration value which is read from a free-format ascii file. The concentrations must be listed in the file in order from node 1 to node NN. Each line can contain one or more values.

## Initial concentration for zones

* izone, czone...end Zone number, initial concentration.
This instruction takes as input a list of zone numbers and initial concentrations. Nodes that are in the currently active media (see Section 5.8.1), and that are also in elements whose zone number is in the list will be assigned the listed initial concentration value. All other nodes will be assigned an initial concentration of zero. If a node straddles the boundary between one or more zones, an average initial concentration value is assigned.

## Initial immobile zone concentration

* val Initial concentration [M L$^{−3}$].
All nodes are assigned an initial concentration value for the first solute only.

## Initial immobile zone concentration from file

* fname Name of the file which contains the initial immobile zone concentration data.
All nodes are assigned an initial concentration value, for the first solute only, which is read from a free-format ascii file. The concentrations must be listed in the file in order from node 1 to node NN. Each line can contain one or more values.

## Restart file for concentrations

* transport_restart_file_name Name of the file which contains the results of the previous transport solution.
All nodes are assigned an initial concentration value which is read from the file. This allows concentrations from a previous run to be used as initial conditions for a subsequent simulation, for example, if one wants to carry on the simulation further in time without restarting from time zero.
Since, by default, concentration values for the last time step are output in BINARY format to a file with the suffix prefixo.cen, these are always available for restarting a transport run. It is recommended that this file be renamed in order to avoid accidentally overwriting it and changing the restart conditions for a later run.