Pond plus ducks

Hi all :)

So I'd like to dig a pond and add ducks, but I've a couple of questions.

Here's my plan:
I have a terrace of land just below the well that I can't do much with because it gets too waterlogged in heavy rain. It's around 30m x 15m, roughly rectangle. It's at the bottom of my slightly sloping land, above the neighbouring land (uninhabited) by 1-2m which is held back by big boulders and a dry stone wall.
There is a channel leading from the well overflow hole, which is at ground level on that terrace, to lead the water out the side of the terrace and down into the neighbouring land and away.
So I want to dig the pond on that terrace, and divert the well overflow channel into the pond, and add an overflow channel at the other end of the pond to join up again with the original channel.
The topsoil is sandy clay, the subsoil is heavy clay.
The water in the pond will be on the same level as the water in the well. Although the well is very slightly uphill from the terrace, it's also right next to the terrace and would be about 5m from the edge of the pond.
The well is ancient, stone, 3-4m deep before it overflows. That depth might improve with cleaning. I'm looking into it.
I'd like the pond to be at least 15m long by 10m wide (for 6-8 ducks). I'm not sure how deep it will be, but I'd like at least 2m.

And then I want to install ducks so I can eat them.

What effect will this pond have on the terrace and well? Erosion? Landslips?

Is it feasible to expect to refill the pond in the very dry summer months from the well, which can get low (below ground level) in summer?

What effect will the duck shit have on my well water? I use the well water mainly for plants and trees, but I fill the stone tank next to it in the summer and have a dip in there. Contamination?
Because the land is slightly sloping with the well uphill there wouldn't be any backwash, but maybe seepage?

I'm in Portugal, btw.

All thoughts welcome xx

PS. Pics not possible. The grass is 7ft high down there :)

I identify with your ambitions, and have dug a pond for ducks and used the overflow to passively fertigate my gardens below. I would be concerned about well contamination though, especially for such a shallow well. A deeper well would have more filtration through the earth, but could still be contaminated by overstocking of any animal around it. Ducks also don’t really use water deeper than 1m, and really like the areas below .5m that they can get their bill down into the muck while having their butt in the air. My experience is with muscovies, which are great in my opinion for many reasons, one of which is that they don’t really need a pond, just a clean tub they can submerge themselves in to clean off. Of course they love a pond, but if it’s a matter of the person feeding them getting dysentery and becoming unable to feed them, I think they’re happy settling for some kiddie pools, or a lined pond. It’s not my ideal either but I am in similar situation, with a pond that I’d love to have ducks in but it is above my spring that is my drinking water. I wouldn’t risk it without some serious filtration designed into the system.

Thanks Ben.

Contamination does seem likely.

I might need to wait until I can get the well cleaned out.
Or buy a second hand bathtub and chuck some muscovies in :)