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How Much Water Do You Need for Hiking and Mountaineering?

Nothing can ruin a day in the mountains quite like dehydration. If you're not careful about keeping up with hydration on the trail, it's easy to fall behind. When that happens, your body can shut down surprisingly quickly.

So, how much water should you be drinking during trips into the mountains? In this guide, I'll cover everything you need to know about how much to drink, how to carry it, and how to take advantage of backcountry sources.

How Much Water Do You Need?

Let's start out by talking about how much water you actually need to stay hydrated. If you're looking for a quick, simple answer, 0.5 to 1 liter of fluid per hour is a good rule of thumb.

Of course, the real answer depends on a variety of factors: temperature, humidity, wind, elevation, your fitness levels, your sweat rate, and how hydrated you were at the start of the day all play a role in determining the amounts of water you need to drink.

If you're not sweating much, you might be able to drink as little as half a liter every one to two hours. On the other hand, if you're climbing a sunny slope in midsummer heat, you might need more than a liter per hour.

The best way to figure out how much you need is to keep track of how much you drink and how you feel over the course of your hikes under different conditions.

How Much Water Should You Carry?

Another common conundrum mountaineers face is how much liquid to carry. Water weighs in at two pounds per liter, so it's much heavier than food or gear. If you need six liters throughout the day, it's important to plan ahead so that you won't be carrying all of that at once!

The key to deciding how much water to carry is to plan ahead. Look at your maps and past trip reports to find out where there are water sources along your route. Then estimate how long it will take you to travel from one water source to the next, and calculate how much you need to carry based on that.

Ideally, you should carry at least a little extra in case the terrain is more difficult or more exposed to direct sunlight than you expect.

In order to refill water safely, you'll need a filtration system. There are many different types available, including pumps, gravity filters, squeeze bags, and Steripen UV filters. Any of these filters can make water you find in a backcountry creek or lake safe to drink, so choose whichever option feels most convenient for you to use.

Never drink untreated water in the backcountry except in extreme emergencies. As bad as dehydration is, it's still much better than getting a parasite like Giardia.

How to Carry Water: Bottle vs. Bladder

Another choice you'll need to make is whether to carry your water in a bottle or a hydration bladder.

In my experience, I much prefer using a bladder. They enable you to sip without taking off your pack, so you're more likely to keep up with water intake as you hike. They're also made of flexible materials, so they collapse down when you're not carrying much water.

The only real downside to using a bladder instead of a bottle is that it's hard to know how much water remains inside the bladder. However, you can develop a feel for how much is left over time - or simply open up your pack and check the water level. 

Water bottles can be convenient because they're easy to drink out of and refill with a water filtration system. If you do opt for a bottle, consider using collapsible bottles since these save space in your pack as you drink through your water supplies.

Ultimately, the choice between bottles and bladders comes down to personal preferences. Try them both out and see which container encourages you to drink more on your next climbing or hiking trip.

Water vs. Electrolytes

While drinking water is a big part of proper hydration, it's not the only part. You also need to think about replenishing the salts that your body sweats out as you hike. Electrolyte loss can be just as tough on your body as water loss.

Unfortunately, backcountry water sources often have very low salt concentrations because they are derived from snowmelt. So, you'll need to bring your own electrolyte mix with you on every trip.

You can blend Gatorade powder or salt tablets into your water, or plan to eat salty trail mix throughout the day if you want to keep your water and electrolytes separate.

The Signs of Dehydration

How can you tell if you're not drinking enough? Dehydration can creep up slowly, but it usually makes itself known through symptoms like nausea, cramps, and headaches. These can be mild at first, and they should go away within an hour or two once you rehydrate. If your urine is a dark color, that's a strong sign that you need to drink more as well.

In extreme cases, you may notice that your body stops sweating. Don't confuse this as a signal that you're well-hydrated or no longer hot. It's a sign that you're severely dehydrated and your body is conserving all the water it can.

While it is possible that you can overhydrate, most hikers and mountaineers don't need to worry about this. As long as you're eating food throughout the day, overhydration is extremely uncommon.

5 Tips for Staying Hydrated

There's more to hydration in the backcountry than just the basics of how much to drink. Here are five tips to help you keep your fluid levels balanced.

1. Keep Your Water Handy

If your water is stashed deeply in your pack, it's easy to rationalize going without drinking. Pretty soon, you're behind on your hydration.

In fact, this is one of the main reasons I use a bladder instead of a bottle. If you can drink without stopping, or if you can reach your water without opening your whole pack, you're simply more likely to keep sipping as you hike.

2. Set a Timer

Especially in colder temperatures, it's easy to forget to drink. The best way to combat that and to stick to your hydration plan is simply to set a timer on your watch or phone. Every 20 or 30 minutes, the alarm will remind you to drink.

3. Replenish During the Morning and Evening

If you're sweating a lot during the day, there may simply be no good way to stay hydrated. Your body can only process so much water per hour, even if you're sweating out at a greater rate.

So, the solution is to recover during the morning and evening. This is especially important during multi-day backpacking and mountaineering trips.

Try to take in as much fluid as you can during the hours when you're not moving to get your body back to its ideal hydration levels.

4. Use Sun and Wind Protection

The more exposed you are to sun and wind, the faster you lose water. Sunburn in particular can cause your body to lose a lot of water very quickly.

Simply using sunscreen or adding a light jacket or hat to your outfit can go a long way towards conserving fluids.

5. Drink More at High Elevations

Your body loses water faster the higher up in the mountains you go. That's because the air is drier and your body has to deal with the stress of breathing in less oxygenated air.

In fact, if you're climbing above 10,000 feet, you should plan to drink an extra liter of water each day. You'll also need to take in more electrolytes at high altitude, even if you don't feel like you're sweating more.

Conclusion

Staying hydrated while hiking and mountaineering is incredibly important. While it takes some trial and error to determine how much water your body needs, you should aim to drink between 0.5 and 1 liter per day while you're in the backcountry. Don't forget about electrolytes, and be sure to adjust your hydration to the weather and conditions.

I live in Bellingham, Washington, at the base of the wild North Cascades. Over the last ten years, I've explored much of the region's steep terrain and endless layers of ridges and peaks, both on foot and on skis, often linking far-flung ridges together to push deeper into the range.

*The information on this site is based on research and first-hand experience but should not be treated as medical advice. Before beginning any new activity, we recommend consulting with a physician, nutritionist or other relevant professional healthcare provider.