On mine you can drive the water pump with just the power steering belt...
The AC compressor belt also runs over the water pump pulley, but in my case the AC belt isn't actually capable of driving the water pump at all, the outer part of the pulley on the water pump for the AC belt has a bearing in it and just acts like an idler. This doesn't seem to be common to all years though, just "some" cars.
Regardless, just the PS belt will take care of things.