Collect water from a pond overflow pipe?

I have a pond that is pretty ordinary, no liners, just one big dam made of dirt, and a big pond. The pond has an overflow pipe that goes from the top of the pipe, down into a stream below, and that usually keeps it from flooding over, on occasion the overflow cannot handle it and the water spills over the emergency spillway. I am looking for a way to collect the water that flows into the overflow pipe, but still have a system flexible enough so that when it pours, I can let the overflow do its job.

Really and truly all i want to do is collect water from the pond without having to dig an all new trench and put in pipes, I want to find a way to use the water from the existing overflow.

I don't understand your question. You want to collect the water from the overflow. So I would expect you'd make a large tank or pond at the bottom of the overflow pipe? Or is that not possible? What do you want to use the water for? How much water do you hope to collect at most?

If the overflow is operating, surely there will be plenty of water about?
I think if you need to collect that water, you will need another wall down stream of the existing wall.
Make sure any water captured downstream does not back up and dampen the toe [ bottom of wall ] of the original dam wall.