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How Much Water Do You Need for Day Hiking?

Water for Day Hiking

It’s important to bring water with you when you go day hiking to replace the fluid you lose to perspiration, help keep you more alert and flush waste products out of your body.  Not bringing enough water can lead to discomfort, while bringing too much can slow you down. How much water do you need and what’s the best way to carry it?

1 Liter every two hours

If you’re actively hiking, it’s good to drink about 1 liter (32 ounces) of water every two hours. That’s a good rule of thumb based on my experience hiking year-round and in a wide range of climates. You might need more or less depending on the temperature, humidity and body weight, but that’s a good estimate of what you’ll need to carry if you can’t refill on your route.

Water bottles are best carried where they are easily accessible on the outside of a backpack rather than being buried inside it. Backpacks with stretch side pockets are convenient, so you can reach back and grab a bottle to sip from while walking. Can’t drink and walk at the same time? Stop for a few minutes every hour and sip from a water bottle while you take a five minute break.

How do you know how much water to bring?

If you have a guidebook, it should give you a time estimate for your hiking route. If you just have a map, calculate the total distance of your hike. Divide that number by your pace in miles per hour. This will usually be somewhere between 2 or 3 mph. For example, I can hike 3 miles per hour on a flat trail. If the distance of my route was 9 miles, I’d want to bring 3 liters. It’s just an estimate of what I need, but fairly accurate.

Does it have to be water?

No. You can drink any non-alcoholic fluid. Water is usually cheap and easily available, but you can also drink tea or juice if you prefer, or add an electrolyte mix to your water to make it taste better.

What about hydration packs?

If you have a hydration pack or a backpack with a hydration reservoir pocket, being able to sip on a hose while you walk is very convenient for day hiking. It’s great because there’s such a low barrier to drinking and having a hose connected to your shoulder strap is constant reminder to take a sip. Buying a 3 liter hydration pack, like the ones shown above, is a good size for a long day hike. If you don’t need all 3 liters, don’t fill it up fully.

How do you know how much water is left in your hydration pack?

That’s one of the problems with hydration packs. You don’t know how much water is left in the hydration bladder when it’s hidden inside your backpack. That’s why some people prefer drinking out of transparent bottles. Hydration packs are super convenient though and you can just open your pack and check to see how much water you have left if you want to know.

Can you drink too much?

It’s unlikely. Your body is pretty good at flushing extra fluids out by making you pee. Peeing on a hike is normal and you shouldn’t be ashamed to ask your friends to let you take a bio break on a hike. The color of your pee is also a good indicator of your hydration level. If your pee is clear and copious, then you’re drinking enough. If it’s bright yellow or even brownish, you need to drink more water.

Can you refill water bottles or a hydration pack on a hike?

Absolutely. If you want to refill using a natural water source like a stream or lake, it’s best to filter or purify your water using a simple product like the Katadyn BeFree or Sawyer Squeeze that let’s you pour your filtered water int your bottles or hydration bladder. A Steripen is also an excellent option if you’re carrying wide-mouth water bottles.

Being able to refill using natural sources on a hike will let you increase the distance you can hike, improve your self reliance, and hiking skill. How can you tell where water will be along your route? It’ll be marked on your map.

Written 2017.

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  1. I usually carry a liter with me, plus an empty water bottle and a Sawyer squeeze filter. It took me awhile to realize how foolish it was to carry water when I’m walking by streams and rivers full of water all day. Now, I just filter water when my bottle is empty, stop by a brook, eat a snack, filter water and drink it up.

    • I do that too but I also like the convenience of not having to stop by carrying a bit more. It can also be difficult to make a group day hike stop because one person ran out of water and needs to filter.

      • I can see where groups would be different, with different fitness levels and water consumption rates. 2 liters would ensure that planned rest breaks would require a water refill, too.

  2. In additional to proper hydration it is important to restore electrolytes, otherwise you risk a dangerous condition called Hyponatremia in which the sodium levels become abnormally low. Symptoms of Hyponatremia are similar to heat exhaustion/stroke and if left untreated it can be very serious.

    The best way to prevent Hyponatremia is to eat regularly and by adding electrolyte tablets, such as Nuun tablets, to your water on hot days when you are drinking a lot. Another good reason to bring salty beef jerky on your hike!

    • I was going to say the same thing. In addition to drinking water, you need electrolytes. The beauty of hiking (instead of running, which is very bouncy) is that you can actually eat real food instead of relying on liquid electrolytes and GU packets. If you drink only water and don’t eat anything, you can definitely get hyponatremia, which is just as bad as (worse than?) dehydration. It’s very dangerous to think that it’s not possible to drink too much water. People have died from drinking too much water. We humans are a delicate balance of just enough water and it’s important to not tip the scale too far in either direction.

    • 1 liter/2 hours is about right for most days.

      I don’t think it is worth bothering with sugary electrolyte drinks or “gu” if you are an ordinary day hiker (assuming you don’t love the taste of said Nuun/Gu/etc). Plain water and lightly salted nuts and dried fruit (“gorp”) will take care of the electrolyte situation and are cheaper. This avoids the bottle/hydration bladder cleaning and the hungry wasps. I think that the Nuun/Gu/etc option is most useful for runners. It is quite hard for hikers with normal renal function to both hike at a reasonable speed and over-hydrate.

      Here’s another vote for “take extra water bottles for training”. If nothing else, at the end of the hike on a hot summer’s day, swabbing down with the left-over water is both refreshing and may make one more publicly acceptable. ;)

  3. On day hikes I don’t mind carrying the extra water for training purposes ;). I also refrigerate water bottles the night before a day hike when weather is hot. Sometimes I cache water on dry routes where I do a double loop.

    • That you shouldn’t do. Your body will not be able to cool as efficiently if you hit it with cold water in hot weather – in fact it will work to keep its temperature at 37 °C and thus warm that cold water even faster than non-refrigerated water. The result is -you guessed it!- you get hotter.

      Save yourself the trouble ;-)

      • Actually, recent scientific studies have shown that drinking cold water is better.

      • * Citation needed.

      • I live in AZ and am a fitness hiker, so I’m out there even when it’s 110F and above. I have found that drinking ice cold water helps to cool me down, especially when I’m climbing.

        I have not found that drinking cold versus warm causes any less cooling efficiency. Just the opposite.

  4. Actually the comment on how do you know if you are drinking enough? Too much water can kill you. Your urine ideally would be a light straw colour, if it is clear then you are drinking too much fluid. Check Google for the correct amount, not some hillbillies granny.

  5. It is possible to drink too much water which can lead to hyponatremia and seizures. It’s more common in endurance racers, etc. but can happen in hikers. Here’s a link to an article which describes the problem;http://wildernessmedicinemagazine.com/1041/articles/1041/eah_pg_epub.pdf

  6. Hyponatremia is clearly a thing, and some people die from it. But just curious. How many people have you seen go to the hospital for heat/dehydration related issues? And how many people from hyponatremia? Because for me, I’ve seen dozens of people with serious dehydration related issues (I’ve ended up in a hospital for multiple days due to dehydration in fact) and pretty much no one with a serious hyponatremia issue. I’ve seen tons of mild electrolyte deficient athletes at endurance races, but they have never been in any real danger other than having their muscles cramp up — they eat a bag of chips and perk right back up.

    I don’t think the emphasis on drinking more water is misplaced with the caveat that two disclaimers are added: ‘don’t be ridiculous with hydration’ and ‘don’t not eat’.

    • I’ve never seen anyone go to the hospital for either of those things but I had a friend on a hike last summer get both dehydrated AND electrolyte-deficient. He was not eating and he obviously didn’t drink enough either. We took a nice break at a stream, drank a lot of filtered water and ate some and then he felt better. So both can actually happen at the same time. And even though he didn’t get bad enough to need medical attention, I’m sure he still felt pretty lousy.

    • As mentioned above, clear urine is actually a danger sign!

      If I drink plain water, it goes in one end and out the other–frequently, with dire results if I don’t “get behind a tree” every half hour! And I’m still ravenously thirsty even though my urine is clear. If I add electrolytes to the water, my thirst is quenched with less water, my urine is normal (pale straw color), I don’t have to “go” as often, and I have far more energy.

      I do try to find an electrolyte that has less sugar and less sodium than most. Salt alone doesn’t do the job, and if I eat salty food, I retain fluid (swollen ankles, etc.). It appears to be the potassium and magnesium that I need the most.

    • A voice of reason. You don’t need Nuun tablets or to muck up you hydration bladders with sport drinks, folks! Bring a bag a potato chips, jerky, salted nuts, etc. and you’ll get all the salt…electrolytes you need.

      • What Philip said. On super hot days, pre-hydrate before you start hiking. On trail drink when slightly thirsty and you won’t have to worry about hyponatremia. Your body knows when it needs more water.

        I wonder how many cases of hyponatremia arise because people have been hammered with advice to constantly hydrate. Drink, drink, drink with no regard to what your body needs.

        Not me. When I’m hiking in 100+ temps, I pre-hydrate, then sip periodically, or as needed when thirsty (such as when ding a big climb and sweating a lot). If I’m out for more than a couple of hours I take electrolyte capsules. I also eat something salty. I am never dehydrated in the least.

    • Following a major surgery seven years ago, I started drinking a gallon of ice water a day and ended up with hyponatremia. I passed out twice one morning and the falls resulted in a broken ankle and high and low ankle sprains. I started adding electrolytes and haven’t had an episode since. I still drink a gallon of liquid a day. The high intake is needed for some healrh issues.

      • …health issues.

        I was typing on my phone with my misshapen arthritic fingers… more health issues!

  7. “I can hike 3 miles per hour on a flat trail. If the distance of my route was 9 miles, I’d want to bring 3 liters.”

    One liter every two hours, huh?

  8. Backpacks w/side water bottle storage: Water is normally the heaviest item carried in or on a pack.
    Bio-mechanically, this is a poor method of carrying water.
    You are thrusting the water bottles forward and back w/each step you take.
    When you remove the water bottle to drink and consume some of it, the bottle on the other side has more or less of the bottle you are drinking from. Your load carrying is now asymmetrical.
    Additionally, you try and return the bottle(s) through the elasticized outer pocket. Most frequently, you have to take the pack off to return it to the pocket.
    Bladders are a better solution in that the load is essentially center on your spine and include a hose and bite valve for on the go drinking.
    However, bladders suffer from the need to be cleansed hygienically, the water tastes lousy and they weigh substantially more than a typical water bottle.
    Regarding electrolyte, I prefer bee pollen. A tiny lump in the center of my palm provided me with elimination of cramped thighs on very hot hike. Additionally, It provides me with a solid source of energy without an up or downer as would a sugary drink. An excellent source of energy and electrolyte.

  9. I’m a hiker and a Registered Nurse. If anyone reading this doesn’t believe the linked scientific article in Nigh’s comment or believe in science, they are showing their ignorance.

    While you are at it try to understand the difference between dehydration and hyperthermia.
    Confuse them at your peril.

    People, drink when you are thirsty, trust your body and stop pushing it to the breaking point.
    When you are hiking listen to your body.
    Take salt and sugar, food and water when you crave it.

    Please try to think this idea through and pay attention to you.

    It’s the journey, not the destination grasshopper.
    (And it sure as hell isn’t the miles.)

    Relax and enjoy the hike.

    Bill RN

  10. Hmmm, lots of, um, interesting theories. Seems like notions around food, diet, and even water are as varied—and sometimes as faith-based—as religion.

    I won’t presume to prescribe for others, but what’s always worked well for me on the trail is to supplement plain water occasionally with an electrolyte replacement drink (currently powered Vitalyte) mixed with some powered coconut water and, sometimes, a bit of a “natural” sugar. For those times when i’m not really hungry and water by itself doesn’t seem adequate, a bit of electrolyte drink hits the spot and keeps my energy level up. I carry a pint-sized container to mix this stuff in. On longer breaks, i’ll gnaw on some gorp/trail mix, or almonds and coconut. I also usually carried some dehydrated bananas (good for potassium).


    I hadn’t seen/heard the quart-per-two-hours rule of thumb. Seems about right, though i imagine it might vary somewhat depending of the factors mentioned as well as the general climate. On some trails in the Grand Canyon not near the river and at times of year when side-canyon springs are unreliable, one might be carrying most of a gallon at times.

  11. As a trip leader, I am constantly concerned when half the group never takes a “separation break”, even on a 7-8 mile 2000 ft gain trip with temperatures in the 70s or 80s.

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