Mark,
Actually, the Kumbh Mela happens every year, but this is a special (Maha, or great) one that occurs every 12 years.
Awesome photos! I'm actually going there (not for that reason), but since I'll be there, I'll join in the festivities for an afternoon. I wish I had a press pass, because the last thing I need is some corrupt police officer confiscating my 1D X.