Today the sun was shining, did the "once" a week top off the pond, have a hose hook up and toss hose out window to pond to fill up in winter. My bottom pond shows the water evaporation as it keeps the tops ponds full, which then spill back down to bottom pond. The bottom pond has a overflow, where the extra water can be carried away to this big tree.
It's good to have a overflow, so that extra water can be overflowed down away from the main pond, to avoid liner slipping and sagging after heavy rain.
We have been lucky this December, lots of Chinnok winds so I have not needed to plug the pond heater in for many days. All the ice is pretty much melted now as you can see.