First I want to make sure we're on the same page... You keep saying rubs, which I interpret as horns rubbing trees... That's just one way that bucks mark their territory... They also make "ground scrapes" with their hoofs.

They make the rubs, and scrapes to mark a territory... The territories are not perfect circles, but are circular in nature. No doubt those ponds will fall within one or more bucks territory. Bucks make the scrapes, and rubs in places were other bucks are likely to find them. So I guess a water source could be a motivating factor to cause a buck to make a scrape or rub.