Do you guys think 40gpm will be sufficient for a "maintenence" well? You know, keep the pond at full pool during dry years like these?
Yes 40 gpm will work fine for that. I use a 45 gpm to fill three 100,000 gallon ponds after draining annually (takes only a couple full days) and it will fill my 1,000,000 gallon pond too if I drain it, which I will this fall.
So you should be good for topping off a pond during dry weather.