There are a lot of concerns about the river levels since last years drought. I can see this due to the web site statistics. And it is an important questions for a lot of people in river cruise forums. People interested in cruising Europe want to know the the water level for a particular month, and are sometimes really disappointed when they learn that it is too hard to say. WHY is it so hard to predict the river levels? Therefore I try to provide some background information on watersheds, river courses and the main areas where the cruiseable rivers in Europe draw their water from.