Hello,
I am not sure whether that is possible or not, but in my case I always do it using Fudaa.
In case you want to use Fudaa, this would be a step-by-step:
1. Open your files (geometry and boundary conditions) in Fudaa.
2. Open a 2D view.
3. Double-click on CULVERTS/WEIRS.
4. Right click on sources-add a source.
5. Select on the 2D view where you want to a source (one by one) and these will be added.
You can edit the source location/discharge/velocity/temperature trough the General Parameters window (as any other KEYWORD). Please find attached an Image that could help.
I hope it helps.
Cheers,
José Andrés.