water/food intake on long runs

I think this is one of those stupid questions that I can't find an answer to because everybody else already knows the answer so there's nothing to talk about...

I used to only ever run about 2-3 miles a few times a week. For 3 miles, I had some water before I ran and after and never had to worry about anything. This summer I started running 5 miles regularly, and have done a number of 8-9 mile runs. I don't have a problem with the 5 mile runs, although it's nice when there's a water fountain after the first 3, but when I run 6+ miles, I start to get significantly dehydrated on sunny days, and even when I'm not sweating profusely, I start running out of energy.

I seem to get the impression that this is fairly normal, but what do you guys do about it? I've heard people talking about belts that hold water bottles. When you go on a 10+ mile run, do you just stick some kind of belt that you stick a sports bar in?

I ride my bike about 30 miles from time to time, and then it's easy to take things with you, but it seems pretty inconvenient when running.