Pond outlet needed

I was looking at a 15 acre piece of farmland which is clearly dead dirt....but that is another subject.

I noticed salt deposits on the soil, this is a clear indication of drainage problem. Well I would like a pond but i am wondering, dont all ponds have overflow? this is just a flat plowed piece of land so what would you do with the water if the pond over flows?

Sometimes there is no outlet, and this creates a salty pond after a while. When you think about it, why is the ocean, salty? The only way that water leaves, is evaporation.

But a fresh water pond needs an outlet if you are planning on having freshwater fish.

I wish i could have fish but i would settle for a pond to irrigate with. If i had things living in the pond, i guess I would have to keep animals out to prevent contamination but if it an irrigation pond, would letting some ducks or other water bird be ok? How would one keep the mosquito population down?