Today we are installing a 14” pipe straight down about 8’, backfilling around it with gravel and dirt, and setting my 6’ stock tank over the top of it.   Geothermal heat!  In Nebraska 

wont happen unless you either have heat or something to keep the water moving...

those pop bottles that everyone talks about - does not work..  if they break than you have salt water = not good.

Our mirafount automatic waters work off of geothermal heat like that but they don't have near the amount of water that your tank will have.

I would sure look into insulating (probably put an insulated box of some sort) around your tank since you won't have anything above ground to help.  (unless you just didn't mention that).