I'm gonna throw in here too with questions. You said it has never had an issue until now so something has changed. What can you tell about changes? Was it the drought and it got low and caused some "cracking" in the clay? Did you have any work done to clear it or clean out the muck in the bottom?
I am just looking for the changes. I wouldn't think the old pond would just start leaking... Just my thought.
Dave

Thanks
Dave
1 acre pond.