beginner's swale for small duck pond

Hello, we have a 1,000 gallon stock tank that we are using for our duck pond. It's hooked up to a swirl filter. On the occasion where we need to dump/clean/refill the pond, I was thinking of digging a 30-40ft long berm and swale system along the fenceline, and plant some trees and shrubs that will occasionally provide forage for our ducks and chickens.

Looking at a recent topo map, the fenceline where I want to dig this is roughly on contour. If I do this without precisely measuring this out, will I regret it?

Also, is it a bad idea to fill the swale with rocks?

Thanks, I'm new at this.

My immediate reaction is "measure twice, cut once". You may be surprised as to where contour lines actually fall. Other than that, I'd say you've got a pretty good idea there. Filling with rocks will probably be ok but if there's a lot of organic material in the water, you may have issues with things clogging up. between the rocks. Good luck and post some pictures if you can.

I think it would be ok to be off contour so long as that meant the water would be flowing slightly away from the stock tank. I would not want the water to stagnate around the stock tank myself. Recipe for nasty.

I have had a lot of luck using water to level my swales. Basically all of mine are dug by hand in the rain. Start at point that you can't move, your tank or pond, and go from there. Also if the gradient ins't too steep a deeper swale and larger berm can accommodate minor changes in the contour. I filled mine with wood chips and it soaks up all the water.