Long runs suck when you carry water. I can't stand the sloshing around of a sweaty water bottle strapped to my waist or even worse... in my hand. Talk about a constant distraction that will throw off your rhythm every time. Instead, take the time to drive out a few miles into your run where you can stash a water bottle or two (depending on your distance).
Even better, get your friend to meet you a the even numbered mile markers with some Gatorade. That would be sweet.
Sunday run in the rain.