Cormac, I'm also about 5 ft. low in North West Texas. Like you, no rain. The non oxygenated well water isn't a big problem. You can aerate it by running it through baffles. Cecil Baird posted his well thought out contraption here once. Essentially you run the water through a piece of pipe where the water stream is broken up by some kind of materials like mid sized rocks before entering the pond. I have splashed the water onto a piece of tin before it gets into the pond. I doubt that these kinds of measure are really needed if you are just adding top off water but I could be wrong (I usually am).