Just a wild hair I had maybe someone could elaborate.

We are thinking that the majority of our leaks are in the bottom of our 1 acre pond. If the lower 1/2 was sealed with a liner, what proportion of seepage goes out the side walls?

I suppose it depends on the soil type..

Any thoughts from the gurus?

Will not work there is no way to mend liner into pond soil to get 100% seal and bond. Best drain pond down locate areas that are leaking and apply clay and knit into existing soil if you have problems in a number of places best to do the entire pond while you have equipment there.If you get a good base down then you can run your clay up the sides and rototill into existing soil and compact. It is possible to seal isolated leaks but consult a pond builder in your area ,could be caused by several different factors.
Good luck

Hi Scott

Didn't really think it would work. We can't get clay very economically so I don't know where this project is headed. Thank you for your input! I appreciate your help!

You want to get a material with 40 to 50% clay so when you mix with exsisting soil you maintain a seal good luck

Scott,
I've had the same problem for the past 3 years. We have had a poor amount of rain for the past 3 years. I have added betonite with not much help. I feel for you and wish I could add a little of encouragement.