I live about 90 miles south of you and have been experiencing the same drought since early May. My pond was dug last year and is down about 4-5" from full. I am not an expert, but assume some of my loss is "new pond" as well, so evaporation (FishinRod) and some absorption could be enough.
I looked at the pictures and would like to ask if they dug a core trench for the dam, did they use a roller to compact anything, and did they see sand or gravel layers or veins? I would guess that it could be that some of the loss is due to seams or veins in the soil not fully compacted.
