Drinking water and remaining hydrated is essential for the human body to survive. I remember during Marine Corps boot camp drinking upwards of 12 canteens of water each day depending on the training evolution. We would take water breaks and have to drink a canteen until it was empty, then hold it upside down over our head showing that we drank it all. In the heat of the moment it felt like self inflicted water boarding, but the drill instructors did it for a reason. Because of the level of physical activity done each day we required elevated levels of water to keep our bodies going.

Searching online you’ll find numerous sources with different advice on how much water you should be consuming daily to remain hydrated. Camelbak has a pretty solid hydration calculator to determine how much water you should be drinking based off your weight, height and age. Generally I have my cup or two of coffee each morning, but after that it’s water for the remainder of the day. On average I consume 64 ounces of water in the afternoon using my 32 ounce Nalgene water bottle.

When I go on day hikes I generally only take a single 32 ounce water bottle. Why you ask? My theory is that if I am keeping my body hydrated through regular consumption of water, then I’m not starting out my hike dehydrated (many do and don’t even realize it).

Here is what Kyle Defoor has to say about hydrating:

As we come into summer and hot weather, hydration comes into play more for training and working out. A common trait I’ve seen in the past few years is the over hydration and a dependency of water in some people.

There is no doubt that during strenuous activity you need to replace water. The question is how much. Training continuously with a endless supply of water makes for an unrealistic real-world scenario. It also hampers peak performance. The introduction of the water bladders to the military has, in my observation, resulted in too many drinking too much and not being able to perform without a large amount of water available. Obviously, environmental conditions will make a huge impact on how much water to drink. In extreme heat conditions, or during very high physical activities more will be needed.

How much?

I believe that during normal environmental conditions, 12-24 oz. of water per hour is sufficient. Genetics will play a part in determining which side of the scale you are on. This should be sufficient water to do anything from running to humping a ruck as long as heat is relatively moderate (75-80 max) and there is some sort of prior physical conditioning present in the person doing the task.

In extreme cases, where environmental conditions are harsh (90 and above, or lack of food, extreme terrain) I think a good intake is up to 2 quarts per hour. Anything over that, and the individual’s effectiveness is coming into play.