Hello!
You can have a look at what is done in the test case Rouse from telemac3d and especially in the utimp.f subroutine.
The part IF(NCSIZE.GT.1) allows you to select a local node number corresponding to global ID 46. Note that there is a subroutine called global_to_local_point.f in sources/utils/bief that also allows to switch between global and local node numbers.
To get your results for water depth, the best would be to print them in a formatted results data file, see corresponding keyword. To write in this file, simply add a line like:
WRITE(LU_file,*) AT,H%R(your_local_node_ID)
LU_file is the logical unit corresponding to the formatted result file you use. See more info in the .dico file and I guess in the user manual.
AT is the current time step in seconds
Good luck!
Best regards
PL