Welcome to Pond Boss!

Nasty muskrats are one almost sure-fire way of making a pond leak. You may have fixed some leaks when you repaired the dam yourself, but perhaps there were still some muskrat holes that allowed some additional leaks.

I think the easiest way to analyze your "spring fed" question, is to pump your pond dry. If it stays dry, then it is NOT fed by long term, stable springs. However, many times the springs themselves can be seasonal, or at least affected by longer term precipitation trends. During our most recent 3-year drought, my two spring-fed ponds went dry because the water level in the aquifer dropped lower than the bottom of those ponds.

If you can pump your pond dry during a wet spring (for example), then you have probably confirmed it is not a groundwater or spring-fed pond.

If you do determine it is a spring-fed pond, and decide to go the pond liner route, do you have enough surface water flows (or an alternate water source) to keep the lined pond full?

Good luck on your pond renovation project!