It turned out the reservoir was very empty. So I filled it. Nothing leaked out over several days, though the car stayed in the driveway. Weatherdude indicated that he, too, had added coolant recently when the light came on and that his was very low as well. Not to worry, right?
Today we did a landfill run and Weatherdude put the stinky mess in my Volvo, partly so we could test drive it. It's about 20 miles to the landfill with a stop at the farmer's market on the way. At the landfill, a good 5 miles from any source of water or coolant, the light came back on. Ironically, this is where my light came on when it was a false alarm several years back: at the landfill.
The reservoir still had coolant/water, but the level was lower than it had been when we started (I had checked). We banged on it in case the indicator was stuck. The light went off. It then came back on. I pulled over. Weatherdude was able to see some wet spots indicating a probable leak, presumably when under pressure. We still had about 4 miles to go, but he thought the car would be fine getting to the nearest place in town. But that was pretty much it for me. I couldn't look at that indicator light coming on and going off. So we switched drivers.
Water was added and we finished the drive home with the light not coming on again. Presumably something is going on and the car needs to go to the mechanic.
But, we thought at the same time, "this is why we got the new car." Living in the country, things like this can happen when you're pretty far from any real assistance. (Someone at the landfill would probably have had some water.) And with Weatherdude with me, no one was home to bring another car to us. I was most glad to have someone with me so I could deflect my sense of panic that my Very Wonderful Vehicle had, well, limitations now. That my beautiful 225k car was no longer perfect and might have tires of clay.
I drive 20k a year, mostly by myself or with Miss E in the car. I got into my seat this morning and felt a sense of "ah!" that the seat was set for me and was exactly how I like to sit. The VW has yet to prove to me that it can adjust to a position I find comfortable. But I will try very hard to find that position. Because for now, that's the new long distance car that will likely rack up a good 15k per year.