Need some advice on renovating a 1/4 acre pond on a property that boards dogs.

A little backstory:

We purchased a 15-acre property with a nice house and a big barn 20 years ago. At the time, there were two small ponds, one a runoff pond at the bottom of a steep incline on both sides. The other pond was simply overflow for the primary one. Both were full and thriving with frogs, turtles, and fish (?).

About 10 years ago, the secondary pond dried up, almost overnight. Then slowly the primary pond has been losing volume so that this year, even after huge snows and rainfall, you can see the bottom and the water is almost gone.

The pond is critical for the operation of the dog boarding business so I need to do something.

I have reached out to some locals who suggest I drain it, dredge it, find the source of the apparent leak, reline it with clay, and reroute water to it.

I am a total novice in this area. Does this sound correct? Advice? Pitfalls?

Thanks in advance.