Initially I have more questions than answers. However bare with me.

Why do you need the pump to be above ground? Will this be electric, diesel? I would think that an above ground one could be noisy, but I really don't know.

I have a well I use to keep my trout pond cool, and top off my other ponds, that has a 1 1/2 hp. 220 volt submersible well pump. It's inserted into the well casing about halfway down, and the water keeps it cool. It's rated at 45 gpms which of course is 2700 gph and 64800 gpd. I run it 24/7 in the summer. Cost for electricity when running 24/7 is about $100.00 per month. But I sell the fish I raise, and recoup my costs, so this is not prohibitive. The well is 88 feet deep although we hit water at about 30 feet.

This well pump is about 4 inches in diameter and the well casing is 4 inches which is standard in our area. You can go with larger diameter well casings for more flow with larger pumps.

I believe the only limiting factor on distance is how much pipe you want to put in. My well is about 100 feet from the first pond and flows downhill underground through a 4 inch pvc pipe that was glued together in sections. Due to severe winters here in the north we decided to bury it, but in retrospect I believe as long as the 51.6 F. water is moving there is no chance of freezing. Additionally I don't run the well in winter anyway.

You don't need much of a slope for the water to flow, in fact, water will flow on a horizontal plane. Just drop some on the floor and you will see!

As far as a holding tank that may depend on the size of your pond. As you know water coming out of the ground tends to be void of oxygen with rare exceptions. If your pond was really small, say under an 1/8 of an acre and the flow was good I would run the water through a packed column (I have a homemade one) for aeration and to blow of nitrogen gas and possibly C02 before dumping into the pond. But if your pond is 1/2 acre of more I would simply attempt to dump it in so it drops and splashes into the water. If by some chance your well head is higher than the pond, (this is my case) then you can actually raise the pipe at the end, as in adding an upturned elbow, proportionally to the drop in height from well head.

I hope this helps some.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.