There is an O-ring seal between the water pump and the block that may have gone bad. If the pump itself is not leaking, I would suspect the seal.

I had the same problem you describe,. I spent lots of time under the car trying to pinpoint the lead and it seemed to be coming from behind the mounting bracket.

The bad news is that you have to completely remove the water pump to replace the o-ring. If you're going to go through the trouble of removing the water pump, you might as well put on a new one (unless you have time to spare for that sort of thing).