I just popped the hood and checked to see which pump is making noise.
When car first starts up, water pump comes on at normal speed after a few seconds. There are no warning lights on dash at this point. Then about 15 to 20 seconds later, the yellow warning light comes on, and the water pump RPMs increase.
The pump making the noise is on driver side under the battery - I believe that one is OK.
The other pump, a small one on passenger side, is making no motor noise. It does make a gurgling sound, and some bubbles are appearing in the reservoir above it. I pulled the power plug for the pump and noise didn't change at all, so it is not running at that point.
Both reservoirs are full, and I am not seeing any leak issue.