Robs:
I have the same situation, but my groundwater is very high. Last year my pond was 9' low (feet not inches).
You will have to check to see how much watershed feeds those areas. Your counties NRCS office should be able to do that for you for no charge.
You then have 2 other options. 1) Use a polymer based product like seekleak (Call Tom @ 402-730-4897), incorporate it into the soil and compact it. Fill with a well or pray that you get enough rainfall and runoff 2) Use a pond liner, then cover it with 12" of soil. Then pray that you get enough rainfall and runoff.
BUT, I am guessing that you will need a well to help keep it full due to evaporation. I pumped 3.2 million gallons of water into my pond from Jan-April this year and rainfall helped top it off.
This company can make a liner up to 1.2 acres in size that is one piece.
https://www.btlliners.com/Their liners are lighter in weight than most other companies liners, and are tougher.
