Kelly Duffie,
Sorry so long to get back to this. I had an emergency regarding a property dispute that took my full attention.

The lilies are protecting the pond from evaporation because they protect from direct sun and wind contact.[my hypothesis]
Thank you for your control advice. There are so many ideas out there. I have been doing weed razor manual removal and I am strong and able but it is one heck of a job!
The pond used to be full of fish and now it seems inactive at best.