I would use the well even if it takes a month to fill the pond. Late winter and spring rains with your well water should have the pond full by early April. The sooner you get it full after they are finished the better. then you can asses the water holding ability. There are several good threads here to determine amount of leakage vs evaporation. You should be able to monitor water level up and down on your dock posts.
Thanks for the advise Bill.
I have read in several places where posters have dug separate wells to keep the pond level full. Other than be in close proximity to the water source what would be the advantage as I assume the water source (aquafier) would be one and the same.