Hydration Strategies at Altitude

Water is the medium in which all cellular function occurs. At altitude, the environment is actively conspiring to dehydrate you. A 2% drop in hydration can lead to a 20% drop in physical performance.

The Insensible Loss

High altitude air is cold and extremely dry. Every time you exhale, you lose moisture. This "insensible water loss" can amount to 1-2 liters per day—before you even sweat. You might not feel sweaty because the perspiration evaporates instantly, tricking you into thinking you are dry.

Electrolytes: The Spark Plug

Water without salt is useless. In fact, drinking pure water while sweating heavily leads to "hyponatremia" (low blood sodium), which can be fatal. Sodium drives the thirst mechanism and helps retain fluid.

Urine Color as a Gauge

It's primitive, but effective.
Pale Yellow: Good.
Clear: Over-hydrated (flushin electrolytes).
Dark/Amber: Dehydrated. Drink immediately.

Conclusion

If you wait until your mouth is dry, you are already behind the curve. Drink early, drink often, and salt your water.