Hitting the sand/clay mix well before the water started coming in, makes me think there was a clay bottom to this pond at one time. It does not seem to drop steady, hot/windy days it drops more than cloudy cool days, as expected. During the cooler months, it does not seem to drop much, if any. I would guess evaporation more than anything. As it gets dryer, maybe the trees around the pond start pulling more water out during the day as well? I guess what I am getting at, I do not think it is a steady drain to the water table by any means.
As another reference, here is another picture taken in March of this year. The test hole was dug approximately where the puddle to the left is in this picture.
