Welcome to Pond Boss, Luke.
Most of the "generic" discussion on the forum about building ponds is for sealed ponds that are filled via surface run-off (rain). Your project is of a different type.
Do you know how stable the groundwater table is on your property?
If it is stable enough for your purposes, then you could actually just build a groundwater pond that is connected to your local aquifer.
However, this pond will always look a bit "strange" since the water level will (usually) be 4 feet down in the bowl you excavate for the pond. A supplemental water well will NOT work in that situation. Any water you add will slow/ly/quickly seep into the aquifer and your pond will return to that water elevation.
If the groundwater pond idea does not work, do you have any clay available on your property? If yes, then if would probably be more affordable to use that clay to make a sealed type pond. If you do not have enough watershed available to keep that pond full, then your supplemental well would work.
If you do not have good clay close, then a pond liner would probably be your best and most affordable solution.
You are correct that a pond liner may balloon in a high water table situation. The physics gets a bit complicated, but the simplified version is that if you keep the water level in your lined pond higher than the "unrestrained" water level of your aquifer, then you should not have a ballooning problem. (If there is lots of high ground nearby and you have a partially constrained aquifer, then it is possible to have ballooning.)
There are some vents and underlayment drains that can be installed to address the problem, but most (all?) must be installed during the initial construction.
I wonder if you could just bury a length of corrugated plastic "drain tile" pipe in the sand across the length of your pond before you install the liner. Run the end into a little pit or vertical culvert. During a wet spell, you might be able to pump down the groundwater directly beneath your pond if needed.
I am not a liner expert, but we do have a few in the forum. Keep reading some posts to learn some more background. If you do end up planning a pond with a liner, maybe come back and get some advice from the experts during the planning stage.
Good luck on your new pond project!
