Where does the dampen come from within larger man-made ponds? More particular, a pond the size of 1 acre +/-. How...

More particular, a pond the size of 1 acre +/-. How are they made and what keep the water smooth?
Turf, grass seed or neither?
Answers:    They have pipes and pipe it surrounded by.
How do i take seed form Gerberas?
Around here(Nebraska) the ground water is high-ranking enough to stuff them, other places it has to be from runoff after a rainfall or snow or I imagine they would enjoy to pump the water to compress them.