Outdoor_Quest, I'm just curious. Are you asking this question from a "How much water should I plan to take along?" perspective, or more of a "How much should I be drinking during this activity?" perspective? We've had some good answers to the latter question, but the former question is very difficult to answer because of all of the variables involved.

The best answer is probably just doing a personal experiment yourself in the conditions you're interested in, observing how much you drink and whether you think it was adequate or not, and making a decision based on that experiment. Some people are apparently part-camels while others seem to run out of water while the car is still in sight.