It seems intuitive that "head" pressure would depend on the total weight of the water in the pipe (ie, a big pipe fill of water would have more pressure than a small one), but it actually doesn't - it only depends on the height of water.
A thin vertical tube full of water that's (say) 4ft tall will have exactly the same pressure at the bottom as a 4ft tall barrel of water, or a 4ft deep pond. It's also the same pressure as a 500ft long pipe full of water that has one end 4ft higher than the other. They sure don't weigh the same amount.. but the pressure per square inch is the same.
Of course, that changes when the water starts to move - if you push 3000GPH through a horizontal 4 inch pipe, the pressure at the pump end is very low. Try to push the same flow through a garden hose, and the hose will probably explode.
Still, it's kind of a moot point - a valve big enough to shut off any pump you'd want in a pond, would probably cost more than a second run of pipe anyway