Yes, technically you are correct. It is not the "only" source of water. This is the second year I had bees at this location. The first year a couple of guys ran a sizable chemical free garden right next to the pond and the hives which was watered regularly. There was no noticeable difference in production or survival compared to the other bee yards. That was not the case last year. There is a small "creek" (and I hesitate to call it a creek) located through some woods considerably farther away than the pond that has water in it in the early spring, and then the rest of the year only water a short time after it rains. Given that the yard is in relatively flat farm ground other than the patch of woods, and the pond is less than 100 yards away from the hives, I think it would be safe to assume that this pond would at least be called the "primary" consistent source of water for the bees, especially at the time of year the pond was treated.