you run the risk of freezing ground pushing in the sides. Once you have
plants and/or fish, you will definitely need to leave the water in.

I agree i wouldn't drain it either with or without fish in it.....I don't think
it would be good for ANY kind of liner to be exposed to below freezing
temps.....if it is filled with water it will not get that cold Jerri

http://www.fringeweb.com/Ponds/JerrisPond