I think banning water from festivals is a poor idea.   However, I do beiieve the promoter or people who run the festival have the right to make the rules for their event.    As the customer, you have the right to decide whether you want to purchase their product.

If they ban water and that is an important issue to you- stop going to the festival.    If enough people feel the same way the promoter will either change the rules or go out of business.

Some festivals allow tape recorders and VCR's.   Other ban them.   It is their perogative to set those kind of rules- no matter how stupid they seem to other people.   If you don't like it start your own event.

PS:   On the subject of water rationing- the funniest remark I heard was about 5 years ago during a draught.   Our city went to a odd/even lawn watering system.   They interviewed an inner city woman who insisted that there was no odd/even system.    She stated that she lived in an even numbered house, but every time she turned on the hose on odd numbered days, the water continued to come out.    It is hard to aruge with stupidity like that.