Hi, kdub.
I don't know if I actually get dehydrated faster, but I'm certainly more aware of it, having been reminded by several docs not to let myself get dehydrated. I tended to drink a lot of water even before my donation, but I definitely notice when it's been a bit too long since my last drink. I know that, before the donation, I would often wait to get home, rather than buy a terribly-overpriced bottle of water in town. Now, I've trained myself simply to pony up whatever necessary, if I happen not to be carrying a water bottle in my brief case. On the scale of things....
Actually, I do think that I get knocked-out a bit faster, since the donation, if I haven't been drinking enough water. Especially first thing in the morning, I just seem to "run better" if I have a glass or two of water.
In any case, it's good to drink lots of water. But, if you notice significant changes, etc., don't be afraid to check with the doctor.
Be kind to your (one) kidney, and hopefully it will be kind to you!
Stay healthy,
Snoopy