The first reason for dehydration is the drier and cold air. This literally pulls the moisture away from your body. And also sweat will be absorbed very quickly by the air. And then your body continues to sweat. The physical effort of winter sports also means that your body uses more moisture. Sporty skiing provides extra moisture loss
Furthermore, there is also a reinforcing factor at height and that is the fact that you will breathe faster in the mountains because there is less oxygen in the air. Add to this the physical effort of skiing and you breathe even faster. That way you lose more moisture. The higher the area the more you will suffer from this. This also applies to the acclimatization process in which you will urinate more at the beginning of your stay. Lose weight by drinking water. The higher the harder your body needs to acclimatize and the more fluid you lose. The latter applies mainly to the really high areas.
How do you know if you are drinking enough water. So drink enough, several liters extra per day. A good indicator is the color of your urine when urinating. This must remain light colored. The most important thing is to get enough fluid, the type of drink is less important, but no alcohol of course. During strenuous efforts, read sporty skiing, off-piste skiing or ski touring, isotonic drinks are sometimes just a bit more effective, but more about this soon. Soft drinks, up to 7 cubes of sugar. Healthy drinks instead of water.