Hello,
I am not an API specialist, but I have a few questions or suggestions.
Where have you found the name FLOWRATEQ?
Reading the TelApy user manual available here:
wiki.opentelemac.org/doku.php?id=documentation_latest
or the api_handle_var_t2d subroutine (in $HOMETEL/sources/api folder),
I can read that this variable is for solid transport flowrate, not for source discharge. This latter variable seems to be currently available for TELEMAC-3D, not for TELEMAC-2D.
If you need to add a variable not available, you should read the TelApy user manual, in particular the subsection "How to add access to a new variable".
Hope this helps,
Chi-Tuan