Ouch, that sounds rough on your leg, but I guess they say you are lucky to have one! Hope the knee replacement helps, my uncle just had it done on Dec 31.
My pond ran over a few times last spring and I kept letting some water out the drain because whenever it ran over it skimmed my YOY fry right off the top and down the overflow by the thousands. I settled on trying to keep it right at 8 inches below full pool, and since middle of May 2020 it has stayed right there and hasn't fluctuated 2 inches either way since, we would get a little rain to bring it up an inch then pro evaporation it would drop an inch, it is setting on about 7 in low still. I was amazed at the minimal effect that evaporation did have. almost nothing.

All the really good ideas I've ever had came to me while I was milking a cow.