In a perfect world somewhere upstream would be enough elevation gain that you could gravity-feed the pond through a pipe and some filters. However I think that is frowned on in most areas.
But yeah, the going estimate around here in WNY is ~2K per 1/4 acre for ave 10ft no transporting of soil. My desired 1 acre pond wound up deeper with less surface area due to some miscalculation but since I like to dive, I will take it. So if it were around here for a 3 acre pond averaging 10ft would be $24K, probably more as you have to move the soil a greater distance unless you make islands and peninsulas (which I would have done in a larger pond) to prevent having to move the soil so far.
I heard around here we need ~6 acres of watershed per acre of pond, but if you get really lucky and hit a spring which is sourced by a lot more area than you think, then bonus! I didn't get lucky in the pond, but there is a good spring that dries in the summer up hill that runs into it for a few months out of a year.
To be perfectly honest I don't know what my watershed is, but I think it is around 10-12 acres or so into my 0.7 pond based on the little research I was able to do myself. I am a tad worried that some of our drier summers will cause quite a variation in height, but not about to drain drinking water tables with a well to fill a pond. I don't believe 6 acres per 1 acre claim either.
Annoyingly just down the road a quarter mile away a new house was built with an artesian (sp?) well which had so much back-pressure the water sprayed out of the lid like a fire-hydrant until they could cap it better. No pump required. I would probably hit the salt layer below before I saw water like that and be able to raise ocean fish. Oh, and we get natural gas in our wells which makes things "interesting".
-Mark
