Hi Clemens
In the telemac system, if you add a fortran file to your steering case, the new subroutine replace the previous one even it was already compiled.
You could easily check this capability by adding a write with a comment in your fortran file.
Nevertheless, if you prefer to implement this updated subroutine in the default version of telemac you should recompile the whole or part of the system, depending on which program the new fortran file is included.
For example, if the new fortran file is in bief or parallel or paravoid, you should recompile thhis library and all the programs (artemis, sisyphe, tomawac, telemac2d and 3d)
If the subroutine is in telemac2d, you should only recompile telemac2d (because it's the higher level).
Just take care that telemac include sisypeh and tomawac libraries so if the change is in sisyphe, you should compile sisyphe and Telemac.
I hope it's clear for you now
Regards