Well thanks for all the @addy's! I will tell you my thoughts, may or may not work, but should based on how my bees have acted.
You need to break their habit. They have communicated to all the bees in the hives, that this is the place to drink from. To break the habit you need to make the water not accessible to the bees, a netting (fine so they can't get though, shade cloth, burlap etc.) Leave it for 4-5 days, maybe longer (it will take some time with that many hives of bees).
While they are learning that there is no water source there, give them an alternative source. My bees do not drink from my pond. Maybe once in a great while I will see one a lily pad.
They do drink from the small slow flowing ponds, which I allow algae, string algae, plants to over crowd. They do drink from my deck pond, which has a ton of plants and only flows a few times a day with the big pump, circulates with a small pump. They love my streams small ponds full of aracharnis. They use it to land and drink.
The other place they love to drink from, if you prefer not to have a stagnant pool of water sitting around, fill a tub with some pea gravel and water put in plants, creeping jenny, grab some algae if you have it, fill with pond water, they love smelly water btw. Keep the water level just at pea gravel height. A good way to do this is to put in a liter bottle full of water upside down, it will drain out as the water level changes in the gravel.
Once they learn that here is good water to drink safe, easy to reach, they will fly back do the wiggle dance and tell all the other bees drink here. Put this tub as close as possible to the hives, watch the flight path ,of the bees, that will tell you the best place to put it.
I have some stuff I put in their sugar water that drives them crazy, it smells great, pm me your address I can send you a few ounces. Too expensive to have you buy a whole bottle. BTW we add vinegar to their sugar patties that I make for them, they inhale in the winter. I don't think they do not like the smell of vinegar.
Vanilla, lemon grass oil (is used to try and catch a swarm they love it)
Once they start visiting the new water source then uncover your pond. Thinking on it I would leave it covered for around a week, if it was mine. Sucks but it will change their drinking hole.
Oh and another choice, go buy some cheap honey, at their new watering hole sprinkle a little on the pea gravel edge of the new drinking tub etc. They can smell a drop of honey from far far away, it is unreal how that attracts them. If you belong to costco they carry honey real cheap, you could even dilute it. They will come there to eat it and also start coming to drink, wiggle dance with all the other bees come here.
Really sucks that bee keeper won't do anything to help, it is so easy, a tub of water with a small pump and they would drink there. The pump just to keep it fresh.
