Here is an example of springs in a ground water aquifer fed pond, this is one of several old sand/gravel pits fed by 2.5 million gallons per day of flow from the island aquifer in Muscatine, Iowa
The flow of water is predictable on some bodies of water but changes from time to time on others. This pond is just 20 acres of over 750 total in the area. Picture is from the 26th
The only place where I can think of that may have a tappable ground water feed might be something like Ha-Ha Tanka state park in Lake of the Ozarks or similar. Water seeps to the surface through limestone caves/crevices
