Most people will never really venture above 2,500m, let alone with a boat, yet they may experience light altitude sickness. The usual danger zone is in the region between 3,000 to 4,500m as ascent into those altitudes (in the Himalayas, Karakoram and Andes) is decently easy and involves standard trekking routes.

Obviously there are various prevention methods, the most important one being a slow ascent once above 3,000m. The aspects of altitude sicknesses (AMS, HAPE, HACE) are not the issue here but knowing the dangers and symptoms are important once you plan to ascend higher than 2,500m.

Kayaking at low altitudes can be challenging already. Once advancing to altitudes greater than 4,000m, the aspect of lesser oxygen saturation is an issue when attempting difficult rivers. I have traveled and kayaked in altitudes up to 5,600m and never really experienced serious problems in altitude.

Rivers are graded between I-VI with difficult or expert rivers are starting from IV-V with VI being the exemption of navigable possibilities.

Carrying weight (loaded boats can weigh up to 50kgs) and doing physical exercise starts to affect a trained person at an altitude of 4,000m plus when arterial oxygen saturation will be below 90 percent and it takes extra effort and concentration to make the necessary paddle stroke or while doing a portage along a cliff.

But fitness is definitely not prevention for altitude sickness, as most visitors to high grounds are climbers, skiers or other athletes more fit then the average person, yet they still come down with variations of AMS. Slow acclimatization is the key to avoid problems in altitude and descent to lower regions, the only real treatment (apart from pressure chambers) if any symptoms occur.

With many rivers in the Himalayas and Karakoram starting at altitudes between 2,500 and 4,000m and high passes to be crossed for access, it is important to not underestimate the impact of AMS and to be aware of the symptoms. Exhaustion and, in altitudes above 4,000m, also mental exhaustion can and will be an issue for the success of an expedition in high altitude kayaking.

There are only a few rivers in the world which will still be navigable once above 4500m. The usual build up of Mountain Rivers in the Himalayas will give you good waters at an altitude of about 3,500 to 4,500m and then usually descent into deep boulder choked gorges formed by the still young and changing mountains there. The steepest part of the rivers will be over at roughly 2,500m with challenging rapids all the way into the Ganges plains with only 80m above sea level.

Recommended places to try kayaking in altitude are: the Tibetan plateau (recently opening up to commercial trips), the Zanskar and Tsarap Chu Rivers in the Ladakh area (Indian part of the Tibetan Plateau), the Indus, Braldu and other Karakoram Rivers in Pakistan.