Abrupt Water Loss
The water level in my pond dropped about 9-10" overnight after doing a water change. The water level has been stable from fall, through the winter and into our rainy spring. I have an overflow drain that keeps the water at a constant level when it rains.
After a few days without rain I figured time for the first water change of the season. I pumped some water out, put some water in, filling the pond. All seemed well. The next day the water level was down 9-10" (140 sq ft of surface +/-). I filled it again with the same result.
I have a fuzzy memory of this happening before but can't bring it in focus. A search didn't reveal anything close to this problem. I welcome thoughts, speculations to guide me systematically in trying to resolve the mystery.
Thanks - Mike