I hate stinging insects but when my pond went up it was wasp city in and
around as I am a good source of water for them. They even tried building
a nest close by two years in a row which I quickly disposed of.
Chances are is that you do have a nest close by but not visible.
All I can say is to leave them alone and they should leave you alone
especially when you are providing them with food and water.
I tend to do my maintenance later in the day when the wasps are at home.

Otto Pylot wrote:
Our pond just turned one year old this month. However, we have a huge
yellow jacket problem. We had our summer algae bloom a few weeks back
but got it under control. What algae we have now is just part of the
ecosystem. Unfortunately, it's attracting the yellow jackets big time.
They seem to prefer to land on the parrots feather and get water and I
assume the algae that has accumulated there. We've hung those wasp
traps which does work but has not even put a dent in the problem.
Nobody's been stung yet because it appears that the wasps aren't
interested in anything but the water and algae. In fact, they are so
full that they fly slower and will actually run into you without
stinging. I haven't found any nests around our house. Is there anything
that we can do or will they just go away (soon I hope).