On a long dry trail (as per above --the desert!), we usually take a good long drink, and then take 64 ounces of water each. That's a ton of water. But it's going to be a long dry trail, and we don't like getting dehydrated.

We figure on drinking about 32 ounces of water every hour between the two of us--that's actually what most physicians recommend for exercise--so if the trail is shorter, or water sources more frequent, we adjust that accordingly.

We find we are guided by the principles:

1. WE don't like getting dehydrated. ever. It makes you slower, and stupid.

2. You don't get prizes for arriving at the end of the trail with water in your pack. Drink it. That's what it's for.

3. We pump/filter all our water--and that takes time. It's easier to pump a lot in the morning than to stop every hour on the trail, break out the pump, and go to work.