re: New pond dropping 1/2" per day - normal?

Honestly, it could be one or the other, and possibly both, but it’s not uncommon for newly built ponds to have some temporary leakage/water loss as they compact/“settle in”.

Is this an leveed pond, excavated, or combo? Was the USDA-NRCS involved in the design, soil survey made prior to construction? They can be brought in, after the fact, for advice/consultation if needed. Does this pond have a drain - often leakage/seepage will occur around a drainage structure.

Even in heavy clay soils, a pond can be “dug” too deep, below the clay layer, and into a “sand lens” resulting in a slow or rapid seepage.

I’ll attach fact sheet on pond leakage - hopefully that is not the issue and it’s just a settling in issue. Renovating Leaky Ponds

ETA: I’m a fisheries biologist (retired) & worked with pond owners for 3+ decades. Leaky ponds was not an uncommon issue.