Question about how the WRF-Hydro model consider the inflow from upstream

[Lise-Li]

Hi WRF-Hydro team,

I'm trying to establish a WRF-Hydro model for a specific watershed with three upstream tributaries. Since I only have observed streamflow at the basin outlet, I wonder how upstream tributary inflows are considered within WRF-Hydro and how can the inflows from the three tributaries rout to the basin outlet?
If upstream inflows are not considered within WRF-Hydro, in which code file should I make modifications to enable the addition of tributary inflows to the confluence grid where tributaries join the main basin?

Thank you very much for taking the time to check my question! I'm looking forward to your reply.
Best wishes,
Lise Li