Hi Lynn!

A lot depends on your water temperature. As long as your water temperature stays at or above 45 degrees, you'll be getting some benefit from your filtration and your filters and pumps should be allowed to run. Your fish will be active enough to need the filtration. If your water temps drop below 45 degrees, all you are getting is mechanical filtration and since you won't be feeding the fish, biological filtration isn't as much of an issue.

Continued water circulation over your falls will maintain some oxygenation, especially if you've got a lot of turbulence and water movement.

The point at which the falls become a liability is the point when your air temperature drops below freezing and stays there. Water over the falls will tend to freeze in interesting patterns, with the real possibility that your water will be diverted out of the pond, leaving your fish stranded.

I suspect that long-term freeze is rare in North Carolina. Run your pumps as long as you can.

Happy ponding,

Bob