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The Colorado Trail stretches 485 miles through some of the most stunning terrain in the Rockies, but it presents a challenge many first-time thruhikers underestimate: dehydration at high altitude. Unlike lower elevation hikes where you might feel thirsty and think to drink, the combination of altitude, dry air, and physical exertion creates a perfect storm that can leave you dangerously dehydrated before you even realize what’s happening.
Why High Altitude Changes Everything
When you’re hiking above 8,000 feet, and the Colorado Trail regularly pushes past 13,000 feet, your body works differently. The air is thinner, which means you’re breathing harder and faster to get the oxygen you need. Every breath you take releases moisture, and at altitude, you can lose more than twice the water through respiration compared to sea level hikes.
The dry mountain air accelerates this process. Colorado’s humidity often hovers below 30%, and it can drop into single digits. This means moisture evaporates from your skin and lungs constantly, even when you’re not sweating. You might not feel wet or notice yourself sweating because it evaporates so quickly, but your body is still losing crucial fluids at an alarming rate.
Here’s the critical point: dehydration at altitude isn’t just a summer problem. Even in spring, fall, or during cooler weather, your body loses water at elevated rates. The cold air is actually drier, and you’ll still be breathing heavily on climbs. Many hikers make the dangerous assumption that cool weather means less hydration needs. This misconception has ended more than a few thruhikes prematurely.
Warning Signs You Need to Know
Recognizing dehydration early can mean the difference between a successful day on the trail and a dangerous situation. Here are the signs to watch for:
Early warning signs:
- Dark yellow or amber urine (should be pale yellow to clear)
- Decreased urination frequency (you should urinate every 2-3 hours while hiking)
- Dry mouth and lips
- Headache (easily confused with altitude sickness)
- Fatigue beyond normal hiking tiredness
- Dizziness when standing up quickly
Advanced dehydration symptoms:
- Extreme thirst
- Confusion or difficulty concentrating
- Rapid heartbeat
- Sunken eyes
- Little to no urination
- Extreme fatigue or weakness
The tricky part about high altitude is that dehydration symptoms overlap significantly with altitude sickness. Both can cause headaches, nausea, and fatigue. This is why maintaining proper hydration is your first line of defense against altitude-related problems.
How Much Water Do You Actually Need?
Forget the standard “drink 8 glasses a day” advice. On the Colorado Trail, thruhikers typically need 4 to 6 liters of water per day, sometimes more depending on conditions, your pace, and your body size. Hot days, steep climbs, and dry conditions push this number higher.
A practical rule: drink a half-liter every hour while hiking, more during intense climbs or hot weather. Don’t wait until you feel thirsty. At altitude, your thirst mechanism is less reliable, and by the time you feel thirsty, you’re already behind on hydration.
Check your urine color regularly. If it’s darker than pale yellow, increase your water intake immediately. Many experienced thruhikers aim to urinate at least once every 2-3 hours as a hydration check.
Essential Hydration Gear
Water storage is your foundation. Carry at least 3 liters of capacity, but 4 liters is better for the Colorado Trail. The sections between water sources can be long, and some sources may be dry depending on the season.
Hydration bladder vs. bottles: Both work, and most backpackers will choose bottles for easy visibility. But a 2 to 3-liter hydration bladder makes it easy to sip constantly without stopping, which encourages better hydration habits. Add one or two 1-liter bottles for backup, electrolyte mixes, or when your bladder needs cleaning. SmartWater bottles are popular because they’re lightweight, durable, and fit standard water filters.
Water filtration is non-negotiable. The Sawyer Squeeze, Katadyn BeFree, and similar filters are thruhiker favorites because they’re lightweight and effective. Bring backup treatment tablets (Aquamira or chlorine dioxide) in case your primary filter fails. Water sources are abundant on most of the Colorado Trail, but you need reliable filtration to use them safely.
Electrolyte supplements deserve special attention. When you’re drinking 4-plus liters daily, you’re not just losing water; you’re losing sodium, potassium, magnesium, and other crucial minerals. Plain water alone can actually dilute your electrolyte levels dangerously low, causing a condition called hyponatremia.
Pack electrolyte powder or tablets like SALTT, LMNT, Nuun, or Tailwind. These aren’t optional luxuries, they’re essential gear. Use them in at least one liter of water per day, more if you’re sweating heavily. Salt tablets are another option, especially for high-output days.
Water Source Strategy
Plan your water carries carefully. Download the FarOut app or carry updated water source information. Sources that flow in June may be dry by August. Springs are more reliable than streams, and many sections have established water caches maintained by trail angels, though you should never depend solely on caches.
Carry enough capacity to dry camp if needed. Some of the most beautiful campsites are away from water sources, and having 3-4 liters of capacity gives you the freedom to camp where you want while staying properly hydrated through the evening and morning.
Morning hydration is crucial. Start your day by drinking a full liter before you even begin hiking. Your body has been without water for 8-plus hours, and you need to rehydrate before adding the stress of hiking and altitude.
Additional Protection Strategies
Pace yourself, especially in the first few days. Rushing at altitude while your body acclimates is a recipe for dehydration and altitude sickness. Take breaks in the shade when available, and don’t be afraid to take a full rest day if you’re feeling off.
Protect your skin and lips. Use SPF lip balm and reapply frequently. Chapped, cracked lips make drinking uncomfortable, which can subconsciously cause you to drink less. Similarly, sunscreen prevents the increased water loss that comes with sunburn.
Monitor your hiking partners. Sometimes it’s easier to notice signs of dehydration in others. Check in with each other about water consumption and urine color. It’s not embarrassing; it’s smart trail safety.
Eat water-rich foods when possible. Fresh fruit at town stops, and even rehydrated meals, contribute to your overall fluid intake. Salty snacks help retain water, but balance them with adequate fluid consumption.
The Bottom Line
Dehydration at high altitude on the Colorado Trail is preventable, but it requires constant attention and the right gear. Carry sufficient water storage, reliable filtration, and electrolyte supplements. Drink before you’re thirsty, monitor your urine color, and understand that altitude changes how your body processes and loses water.
The Colorado Trail is an incredible journey, but respecting the challenges of high altitude hydration will keep you healthy, strong, and able to enjoy every mile of this magnificent trail. Your thruhike success starts with something as simple as drinking enough water, but at altitude, even simple things require knowledge and preparation.