Cormac,
I may be barking up the wrong tree, but if the pond in question is almost dry now - it may be a never-ending task keeping water later in the year. We are running about 6 inches below normal (in my area), but no where near as dry it will be later in the year. Can you ask a neighbor if the pond usually dries up? If so, maybe you can make some decisions from there...I can�t comment on supplementing water, but it perhaps the well is a good option.