Water that goes into the ground can travel a long distance before ever surfacing, or may not surface at all.
On Bull Shoals Reservoir in N. Arkansas, there is a sinkhole in the Jimmie Creek arm where water enters well below normal pool level for the lake, and surfaces about four miles downstream, below the dam on the opposite side of the river.
You could put non toxic tracer dye in the pond after pumping in several thousand gallons, and see if you can find it emerging somewhere, maybe in a nearby creek.
