Also, I do not really know what you mean by saying that 4.5 acres is a lot of water to backup and manage.
I think I misread your first post. I thought the pond was 4.5 acres big. That WOULD be a big amount of water to hold back with a dam and to manage in terms of muck reduction or to change fish populations.
But the pictures didn't look like a 4.5 acre lake so I went back to re-read and maybe the watershed is 4.5 acres.
How big is the lake? There are some online tools and apps you can download that help you put markers around your pond on a satellite map and it will compute the area for you.
You will need to know the surface area and the amount of water (gallon estimate using the 'acre-feet' unit of measure) if you end up using any herbicide or fish poison.
