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Hydration/How much to drink backpacking in the Mountains

Good morning, since I'm not sure I drink enough last year and headaches can be caused by both hydration and altitude and wondering if there is a base amount of water per mile/hour of activity that is suggested. I've tried to find the advice to drink before you're thirsty, but I'm not good even in real life at drinking enough so I'm wondering how much people try to take in so I can compare it to what I have been doing. Hope everyone is enjoying some great hikes this year.

12 Replies

Hi there!

the amount of water to consume while hiking is a mix of personal preference and some minimum liters per day. 

I recommend a minimum of 1 liter per day, 5 miles or less. The more you go up in mileage, heat, the strenuous nature of the hike you’ll want to increase your water intake. 

for example when I do a 12 mile round trip overnight hike I’ll plan to drink 2.5 to 3 liters of water on that trip. Some people prefer closer to 4 liters and others don’t mind less. 

hopefully that helps!

It does vary a lot.  I've backpacked 6 miles with 2000' elevation gain on a liter, but it isn't long in camp when I am drinking more.  My adult daughter will wipe out 3 liters in the same distance. Dayhiking I can go a lot farther (yesterday, 9 miles, 2600' uphill, not even a full liter gone). A personal guide is the color of urine--deeper orange means you'd best be drinking up. The other thing to keep in mind is salt.  Ironically, drinking too much water can lead to a deficit of salt (sodium)  in the bloodstream and can produce symptoms very much like classic altitude sickness. Here's a 2017 Denver Post article about this.

After getting heat exhaustion (not a happy situation), I've become a big fan of electrolyte gels/powder/tablets.  If I notice my mouth is getting dry, I add some electrolytes and it really seems to help.  Now  I carry some in my first aid kit and hand them out like candy to other people who seem to be getting heat stressed.   

great topic/question, but we're going down 2 different paths

how much water to drink so you don't get dehydrated and how do you tell? 

The best/most common way to tell is the color of your urine.  The clearer and lighter it is, the more hydrated you are.  To get it clear(er), you must drink more - period. 

That said, you'll be 'going' more as well.

dehydration can lead to cramping, but cramping can also be caused by lack of electrolytes (potassium+sodium chloride (salt)), you can be fully hydrated but also cramp up because your lacking electrolytes.

Most backpackers/hiker, especially is weather causing you sweat, will 'tank up' with water containing some off the shelf electrolyte product.

I'm no doctor (obviously), but I advise looking at the ingredients before you buy, you are looking for a combination of SODIUM CHLORIDE PLUS POTASSIUM, if the product lacks either one or just has a wee amount of either, go to the next product.

Anyone up for arguing discussing the effects of caffeine? 😉

REI Member Since 1979

Sure,  +1 for caffeine in moderation.  When in the mountains...High Sierra 8000ft +  I generally use NUUN SPORT tablets ( with caffeine in the morning and possibly up to mid afternoon in addition to morning coffee. I switch to a non caffeine flavor in the afternoon/evening if necessary ( eg: need to flavor the water)

It is probably helpful at altitude...depending on your personal tolerance for it of course.  Like many, I'm an addict to the extent that caffeine is mildly addictive but I have no known deleterious side effects.

Caffeine is a mild diuretic (make you pee).  It may not the best choice to overdo in desert environments (including cold deserts) if water is in short supply.  See section on Fluid Homeostasis...


Hey everyone. 

Obviously everyone's water intake will vary.  And there are differing opinions on what is "correct".  I personally don't think there's only one right answer.  However, I just recently went through a cardiac rehab program, and the licensed nutritionist is a proponent of anyone/everyone drinking 64 oz (approx 2 liters) of water per ordinary day.  More than that to correspond to weather conditions and exertion level.  Among its other benefits, being properly hydrated actually lowers blood pressure.  And, you should try to drink consistently, a little at a time,  not guzzling 1/2 liter every few hours.

And definitely, the electrolytes are necessary to replenish when you're sweating a lot, and should be considered supplementary, not recommended to replace drinking water.

I have found that having a hydration reservoir in my pack tends to make it easier to maintain consistency.

Drink up!  Skol!



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The amount of water and E's you will need vary tremendously with relative humidity, temperature, and level of activity.  As others have stated, monitor the color of your urine.  if you are consuming a normal diet, you usually don't need to add E's to your water, but it i worthwhile to carry some tablets, just in case

In Southern Arizona deserts, I often would drink a gallon of water on the trail when it was sunny and hot. On the California Channel islands, relatively cool, humid, if not downright foggy, I could often go comfortably (with pale urine, no less) on a liter or less.

Water is heavy,  probably the heaviest items most of us carry, but it is beyond priceless when needed.  Take it from an old desert rat.....

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How much water is as important as what's in the water and how to carry.  I recently put 'Electrolytes' in 750ml smart water bottle (and carry bladder too - range from 1-3L depending on length and water availability).  I seldom drink less than 1 L per 10 miles and average ~15 miles / day regardless if backpacking or day-hiking.  I hate the weight of more water, but hate running out too soon more.  I like to hit the car or campsite with <200ml left.


Amen to that @mdf59 !

I have, as I'm sure many others have, occasionally underestimated and run out of water before a hike concluded.  It's a miserable feeling, and can be quite dangerous.  It's always best to carry more than you think you will need.

Superusers do not speak on behalf of REI and may have received
one or more gifts or other benefits from the co-op.