Water leak in interior

[Ole87]

So I am in the process of an interior build. I have all of the interior panels off. I had someone outside the truck using a water hose so I could check for leaks around the windshield as I recently had it replaced.

On the passenger side where the panel covers the heater valve, it looked as if there was a waterfall. Water was basically coming in from somewhere under the cowl I assume and running down inside the wall and inside the panel. Its not coming in the truck and getting on the carpet or anything, but again just pouring down inside the frame. Surely it's not supposed to do that? I have pic of the area that I will post this evening.

Any thoughts on where under the cowl it would be coming from or cause?