I know that running water is supposed to ground out magical forces, but what effect does it have on the making of magically-bound oaths and promises? Does making these oaths over running water ground them out, or are they still legitimate? I don't remember if the books had mentioned anything like this - it's been a while. The only instance I really remember is in Grave Peril when Harry keeps Lea and her minions out of the graveyard due to the flowing water.
Additionally, if oaths CAN'T be made over running water, what about over still or tamed water? Does being on a man-made lake decrease the effect of water on impairing magical forces? After reading The Paranet Papers I was inspired with the idea of a magical riverboat that travels the waterways, secretly entrapping mortals in unintended oaths as well as being a place where supernatural big-wigs could throw down some power.