Are the springs that feed the pond inside the bowl? One possibility is that the very dry weather has lowered the local water table to the point that instead of feeding water into the pond, the springs are now draining water out of it. I agree with your reasoning that there is not a simple, conventional leak; I'm assuming last Winter the ground water level was higher and that the ground water flow has reversed since then.

OTOH 2" - 4" per week is not a whole lot more that I would expect what simple evaporation might total. I know I can lose 1/2" a day here in hot, dry weather. Hopefully some of the other NY PMs will have an idea what evaporation in your area has been.

P.S. As a former Nerd Herd member and current Nerd Herd parent, you have my thanks. Herding cats is probably easier.

"Live like you'll die tomorrow, but manage your grass like you'll live forever."
-S. M. Stirling
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