Fire in a dam

I always enjoy the drive from Cape Town to Worcester via Villiersdorp, although it is a bit longer, so I don't go that way often when I visit my dad. About halfway is the Theewaterskloof Dam, that I remember being completed to some fanfare when I was a child. Wikipedia says 1980, so what I remember is probably the post-completion Nationalist euphoria.

On one trip in September 2010, I remember it as a gloomy, overcast day, I noticed something odd while driving past the dam:

There's a stand of dead tree stumps still standing in the dam (I could have sworn there was; I can't find it in satellite pics), and seeing one aflame right in the dam was quite bizarre. I wonder if the fire started when a lightning bolt hit the stump, or if it was a human-made fire.