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How Much Water Do You Really Need?

Water for Day Hiking

via SectionHiker, Phillip Werner

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.