drinking water, hiking, mountains
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We had just completed a 10-mile trek across the southern section of the Mojave Desert when we hit the water cache. Two days prior, we’d heard there were 60 gallons of water here. Now it was bone dry. I had a quarter of a liter left, but my husband was completely out. If we had been at home in the Pacific Northwest, we wouldn’t have worried much. Just shrugged out shoulders and moved on, confident that a small pond or trickling stream would appear before too long. But this was the Mojave — land of sand, rock, Joshua trees, and not much else. We thought we had taken enough from the last water source, a barely-flowing creek, 10 miles back. We were wrong.

Balancing Water Against Weight

If you’ve never spent time in an arid landscape, you might wonder why someone would cut their survival water supply so close. Why not just carry double, or even triple, the amount of water you think you’ll need before the next cache?

Because water, as it turns out, is pretty heavy: A gallon of water — what FEMA recommends an individual plan on per day for sedentary activities — weighs more than eight pounds. Two gallons — what you might expect to need for a day of strenuous activity (like trekking) in a temperate environment — weighs more than 16. For many of us, that’s already more than our pack weighs. And while outdoorsmen and women may end up carrying that much weight in a pinch, attempting to carry that much on a regular basis will not only slow you down, but eventually wreak havoc on your knees and joints.

But the risk of carrying too little water is even greater. Dehydration will impair your judgement and compromise your body — possibly even leading to death. Taking the time to balance the risks on either side is essential for successfully completing your journey.

Know the Conditions

A rule of thumb for the Mojave is one liter of survival water per person per five miles of travel. But there are a number of factors that can increase or decrease the amount of water you, personally, need. These include temperature (you will certainly need more water in hotter temperatures, and may need less in cooler temperatures); aridity (think of the high plateau in the Rocky Mountain West, where the aridity can suck the moisture right out of your skin); altitude (higher altitudes require more water); and, of course, you. While it is true that the larger you are the more water you’ll need, there is also a huge amount of individual variation. Knowing your own body is key.

The distance between your current water source and your next water source is also an important consideration, as is the terrain you expect to encounter along the way. Carry more water for rough terrain that will slow you down, and also for significant elevation gain. Slight decline on smooth single track, on the other hand, may mean you can get away with carrying less water than usual. Finally, consider where you are stopping for the day. If your planned camp is at or near a water source, you won’t need to account for overnight water consumption. But if you are planning to stop miles from the next spring, bring along an extra liter or two; more if you plan to cook with water.

The Role of Uncertainty

Perhaps most importantly — as my husband and I learned that fateful day — is the unpredictability of water sources. We should never have trusted that a water cache in the middle of the Mojave would stay stocked for long. How certain you are of a water source will depend on a variety of factors. Are you looking at a seasonal creek, or a year-round spring? How was the winter snowpack? Were you able to confirm with someone headed the opposite direction that the water source was running? If your planned water source is dry, how far is the next reliable water? If that’s too far, are you willing to backtrack?

Survival Water — Making a Plan

Eventually you’ll have to decide how much survival water you are taking with you. If you’re traveling with another person, discuss the factors that will impact your carry choice: how far you are traveling, how long it will take, what the terrain will be like. More importantly, discuss your backup plan if the next water source is dry. Will you backtrack? Plow forward? Detour to something off your route? It’s essential to make this decision in advance, as you are more likely to make a rash or foolhardy decision when things have gone wrong, you’re out of water, and in panic.

That day in the Mojave, my husband and I chose to go forward, and make a one-mile detour to a known spring in the middle of the desert. Those five miles were some of the hardest we ever hiked, and when we finally reached the spring, we both inhaled liter after liter of (filtered) water until we felt normal again, and then drank some more before refilling our stocks and heading back into the unforgiving sun. We’d learned a valuable lesson that day: how much water is enough also depends on how much water is in your belly to start with.

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