I have an orifice control curve that's based on the depths at an upstream storage tank. The idea is that when the tank depth rises it uses the curve to resemble the operation of a downstream motorized gate which is an orifice in the model. The gate is to start in the open position (curve setting=1.0) and begin to close as the depths increase, but never fully close. The problem I've noticed is that the gate does completely close even though the curve shouldn't allow it to!

Looking for some ideas to why this might be happening? I've included a picture of the curve and the orifice graph-setting & flow.

Curve.jpg OrificeGraph-Setting.jpg OrificeGraph-Flow.jpg

Another thing that I'm having trouble trying to explain is that although the gate is closing I'm seeing volumes downstream. Why?

Thanks for the help.