Using Tcl/TK to load files and generate input parameters

A question that comes up frequently in ParFlow is how to load in external parameters from a file. This could be for transient forcing for boundary conditions, for Monte Carlo simulation (in addition to changing a random seed) or even in calibration using parameters generated from another program, such as PEST. The example below was from a question recently asked by a ParFlow user and demonstrates how this can be done for a Monte Carlo simulation, though this same approach is adaptable to many other situations.

First, one would load in an array of values from a file using tcl. This is not in the ParFlow manual or addendum, but you can easily do this with native Tcl/TK commands. We use the example from the harvey_flow.tcl. Right now that script does something like this:

set fileId [open stats4.txt r 0600]
set kgu [gets $fileId]
set varu [gets $fileId]
set kgl [gets $fileId]
set varl [gets $fileId]
close $fileId

pfset Geom.upper_aquifer.Perm.GeomMean $kgu
pfset Geom.upper_aquifer.Perm.Sigma $varu
This allows us to provide parameters externally, such as from PEST for calibration (as was done in this example). To modify things, one could do something like this, say to load in file of n Kg's:

set fileId [open stats4.txt r 0600]
for {set i 1} {$i <= $n} {incr i 1} {
set kg($i) [gets $fileId]
}
close $fileId
Farther down in the harvey_flow.tcl script, where we loop over the realizations and change the random seed, we can also loop through the file of values we've read into the arrays for Kg:

#
# Loop through runs
#
for {set k 1} {$k <= $n_runs} {incr k 1} {
#
pfset Geom.upper_aquifer.Perm.Seed [ expr 33333+2*$k ]
pfset Geom.upper_aquifer.Perm.GeomMean $kg($k)...

This approach should work for a number of circumstances as long as you can generate a text file of values outside of the ParFlow simulation script (or one could even generate some relationships within the Tcl script). This can easily be done in FORTRAN, in a spreadsheet or other mathematical program. This approach can easily be modified to load data for wells, boundary conditions or any transient condition as well.