Current article on river level in Hungary & Slovakia
Found this current article (10/2/03) about river levels in Budapest: http://www.csmonitor.com/2003/1002/p07s02-woeu.html
I canít cut & paste because of their copyright requirements but check it out. It states that water is lower now than in September (lowest since 1947) and that 66 passenger hydrofoils from Vienna to Budapest have been replaced by 44 passenger boats because of low water. Seems to me that Viking is well aware of the current and past water levels.