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Posted by Bill S on October 21, 2007 at 9:22:52 pm EDT
In reply to Water posted by sabino on October 21, 2007 at 8:34:38 pm EDT

I'm not sure there is a "norm". In my local hills, I see people carrying a liter/hour for their hike and consuming it all in a 10 mile, 2800 ft total climb hike (5 liters or so), and others who carry only a 1 pint (half liter) bottle and have some left (and the runners who carry nothing for their run of the same trail.

Recommendations are the canonical "1 liter per hour" or some amount adjusted for temperature and humidity (i.e., drink more on a hot humid day, or "winter days at altitude dry you out, so drink more under those conditions").

The real way to judge is the old "clear and copious" criterion. Since each person is different, and every day on the trail is different, the only real way to judge whether you are properly hydrated is by the color and volume of your urine. The normal color should be clear to "pale straw". If it is yellow to dark orange (or darker), you are dehydrated (if it is darker, you are so dehydrated that you are getting blood from your kidneys into your urine). "Copious" means having to go about once an hour. You probably shouldn't worry if it is 2 hours, but much longer is another signal that you are dehydrated.

Another measure is your body weight - severe dehydration, with probable feeling of faintness, dizziness, etc, occurs at 10% loss of body weight (15 pounds for a 150 pound person), and in races, officials in sanctioned races will pull people from the race at a loss of 5 pounds (that's a deficiency of 2.5 liters of water or so). Of course, you don't carry scales with you, but you can learn to judge by measuring your weight before and after an exercise session.

In the Northeast in June (that's getting close to the 90-90 point, certainly day temperatures in the 70s and 80s and humidities well above the 50-60% range), the liter an hour prescription during your hiking is a good place to start. But at least you have plenty of streams to refill your bottle, so you don't have to carry 5 liters from the trailhead (11 pounds of water). You can get by with a 1 liter bottle (ok, 2 bottles, so you can fill one from the stream and put purification chemicals in it while you drink from the other bottle).

You can't judge dehydration by how thirsty you are - if you feel thirsty, you are already significantly dehydrated. Drink early and often.

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