Every hiker knows how important it is to stay hydrated while hiking, but if you love the mountains, keeping hydrated is much more of a task than it is for flatlanders.
Once you start rising, the air becomes drier and has a lower pressure, this means that moisture begins to evaporate more quickly. While this might mean you will feel a little less sweaty, that doesn't mean it isn't happening. In fact, you are losing a lot of moisture from a variety of sources.
In higher elevations, not only are your still losing the same (or more) amount of moisture from sweating, but not feeling it, you are also losing moisture as you breathe.
The less oxygen present at higher elevations makes us breathe faster and harder, and with every breath, your lungs are expelling precious moisture that needs to be replaced. Finally, since you have to huff and puff your way up every tiny hill, even if you are in good shape, this loss of moisture means you need to take in at least a liter or two more water than you normally would.
Dehydration is Bad, Altitude Sickness is Worse
Dehydration at any altitude should be a worry, but it is often much more likely at higher altitudes, and actually more important to prevent as well. Once you get about 8,000 feet or higher, you run the risk of developing altitude sickness.
While dehydration can be dangerous, altitude sickness can be downright deadly. Unfortunately, the early symptoms often mimic dehydration. This means if you feel dizziness, headache, or weak and think it is dehydration, you might be well on your way to serious altitude sickness.
If you don't treat altitude sickness and just continue to hike thinking it is just a wee bit of dehydration, the symptoms will only get worse, primarily the dizziness. This means you run an increasingly higher risk of tripping and falling down, something that, when on a mountain, isn't exactly a great idea.
Luckily, altitude sickness is easily treated with the right medication, which is why many mountain guides will lecture you long and hard about the importance of staying hydrated so they can get you treated for altitude sickness as soon as the symptoms manifest instead of wondering if you are just dehydrated.
The unfortunate side effect of altitude sickness medicine is that it also makes you urinate more. Since our bodies also increase urination from the altitude alone (another way we dehydrate faster!) expect to have go a lot. This means if you are camping you will need to get up every two hours in the middle of the night, so best make the most of the time you do get to sleep.
High Altitude Hydration Strategy
Now that you know that you need to stay hydrated at high altitudes not just because you are losing a lot more fluid that usual, but also because you could accidentally fall off a mountain from altitude sickness, all that is left if to take a drink, right?
Well, if you have never been high altitude hiking before, you don't know, but not only are you're losing more fluid, but you are also less thirsty.
The reason we become less thirsty isn't because of the elevation at all, it is because of the temperature. At lower temperatures, like those higher up or even on winter hikes on flat land, we get less thirsty but still lose roughly the same amount of moisture as we do in warm temperatures.
Unfortunately, since high altitude hiking is particularly hard work, hikers often can't carry the amount of water they need. This is where hydration packs really come in hand. Not only does it make carrying more water easier, but it allows you to have frequent sips of water without having to stop and fumble around with a water bottle.
Of course, even with a hydration pack, even on moderate hikes you will still need to have somewhere to fill-up with water along the way since you will need to intake a liter or two more than you normally would. However, you can still treat the water you get up from the mountains with your typical means even if you are using a hydration pack.
Their wide openings make for super easy and fast refills, and you are still perfectly fine dropping water treatment tablets in, tossing in the old UV filter, or boiling it beforehand, but you still need to make sure it is relatively not scalding hot before refilling the bladder just so it doesn't melt.
So hydrations bladders are the best equipment for the job, but how frequently should you be drinking?
Since you carry your water on your back and are perfectly able to take a drink while walking, you can either sip frequently or take a long draw every now and then, the choice is yours.
However, while it is up to preference, you shouldn't wait until you are thirsty since, by this time, you are likely already dehydrated.
The best advice is to set milestones and landmarks on your hike such as hiking across a small saddle, making it up a hill, or reaching the next vista. After each milestone, you should enjoy your success and the view by taking a drink from your hydration pack. While you may need to adjust depending on your hike and your needs, this is the best way to remember to hydrate even if you aren't thirsty.