You are right. The pivot in the middle is usually a pump attached to a well bringing the water up, then another motor boosts the water through the pipes. It was designed for those fields which were not level enough for flood irrigation (laterals, tubes, etc.) but not too much grade, so the wheels couldn't pull themselves up a slight incline. Beautiful, weren't they? Did you also fly over the fires in Colorado? In their own way , they are beautiful. But so awful. We are 30 miles away, and there is soot in all the windowsills, think how bad it must be closer. And so uneccessary. People, be careful.