How much water, honestly
We've spent four lessons on gain and profiles and spreadsheets. Today we're talking about water, and I'll tell you straight off, this is the one people get wrong the most.
Here's the thing about water. It's heavy, so people pack less than they need. A liter weighs about 2.2 pounds. Two liters is 4.4 pounds sitting on your back before you've added anything else, and your brain does the math and thinks "I'll just carry one, I probably won't drink that much anyway." That's the mistake. I'd rather you haul the extra weight down a trail than run out on the way up.
On my third real hike, I brought a half-liter of water for a six-mile route. Half a liter. I didn't know any better yet, hadn't built the spreadsheet, hadn't thought hard about it, just grabbed a bottle from the kitchen the way I'd grab one for a walk around the block. I turned around at mile two with a headache starting behind my eyes. Not heat stroke, not an emergency, just plain dumb underpacking, and it ended my hike before it really started. That headache taught me more than any article I'd read.
Our air up here doesn't help. Utah County sits dry most of the year, and at elevation you lose water through your breath and skin faster than you'd think, without the obvious sweating that tips you off in humid places. You can be dehydrating and not feel soaked and sticky the way you would somewhere else. That's the trap. You feel fine, then you feel awful, and there's not much warning in between.
How much to actually carry
My rule of thumb, and your mileage may vary depending on your body and the day: half a liter per hour of hiking, minimum, in normal summer conditions. If it's hot, if you're doing serious gain, if you're someone who sweats a lot, push that toward three-quarters of a liter an hour.
So a four-hour hike, at minimum, is two liters. A six-hour hike is three liters. That's before you account for heat or a rough uphill grind.
Do the math for your specific hike before you leave the house:
- Estimate your total hiking time. Use your gain-per-mile numbers from the last few lessons. A hike with real elevation gain takes longer than the mileage alone suggests.
- Multiply hours by half a liter, minimum. Round up, not down.
- Add a margin for heat. If it's forecast above 80, add another half liter per person. If you're hiking after 10 a.m. in July, just plan for it to be hot, because it will be.
- Add a margin for kids or anyone new to hiking. Kids dehydrate faster and don't always tell you they're thirsty until they're cranky about something else entirely. Assume they need what you need, maybe more.
What this looks like at home
Before you ever get to the trailhead, do a dry run in your kitchen. Fill the bottles or the bladder you're actually planning to hike with and see how many liters that setup holds. You'd be surprised how many people don't know their own pack's capacity until they're standing at the trailhead trying to remember.
Weigh it too, if you're curious. Two liters is close to 4.4 pounds. Three liters is over six and a half. Put it in the pack, put the pack on, walk around the block. That tells you something real about what you're signing up for, better than staring at the number on a page.
If your total comes out higher than what your pack holds, you've got two choices: get a bigger pack or bladder, or plan a shorter hike. Don't talk yourself into "I'll just ration it." I've seen people try that. It doesn't go well, and it's exactly how you end up like I did at mile two with a headache and a long walk back to the car.
One more practical note. Electrolytes matter more than people think, especially on longer hikes in the heat. Plain water is fine for most day hikes, but if you're out there four-plus hours in real heat, tossing an electrolyte tablet or packet into one bottle isn't a bad idea. I don't do it every time, that's just me being honest, but on the hot ones I do.
The plain caution
Dehydration headaches can look like a lot of things, and it's easy to write off early symptoms as tiredness or a bad night's sleep. If you start getting a headache, feeling unusually irritable, or notice you haven't needed to use the bathroom in hours, stop and drink, don't push through it hoping it passes on its own. Turning around because of dehydration isn't a failure. It's exactly the kind of decision this whole class is about.
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Before next time: pick one upcoming hike from your spreadsheet, run the water math above, and see what number you get. Bring it to class, we'll compare notes.