I did some work for you.

1. You did not set the boundary of drawingPanel properly.
I changed it to x: -1 t0 1 and y:0 to 2
2. There is something wrong with your code
if ( H1 >= H1max ) Qi = 0 ;
else if (Qi==0&& H1< 0.2)Qi=Qis;

It seems to work now. However, you should change variable values to fit with your case.

You use 12 arrows to represent pipes. It will be better if can use tube elements.

The 3.47 xml file is attached.