Water is continually lost through the normal bodily functions of urination, excretion, breathing, and sweating. The amount of water lost through sweating dramatically increases when in hot conditions or during any kind of physical activity.

The greater the exertion, the more you lose. So it is vital to keep topped up by sipping regularly rather than gulping large quantities with long periods of time between.

2lt should be the daily consumption of an adult and you should take on more when working hard. It is interesting to note that most backpackers are dehydrated more during winter than summer!

During a long backpacking trip you need to be aware that you could need as much as 6 litres per person. 2-3lt to drink, 2lt to wash, clean your clothes, or yourself and another 2lt for cooking, brews etc.

So it is vitally important to be aware of your water sources, contamination and purification as you travel through unknown territory.

Heat Loss

We all want to be comfortable when on the hills and perhaps this explanation about how and why we lose heat, can help you think through the clothing contents of your rucksack and help you lose some bulk.

How we lose heat and why we should use technical clothing

In cold conditions we lose heat through a number of different processes, which if left unchecked will reach the point where the body loses heat faster than it can generate it. In temperatures below 25C the body will automatically lose heat, this will lead to a lowering of our internal core temperature, and if ignored, result in hypothermia and finally, death.

Why women and children get cold quicker

Smaller people, children, teenagers and women lose heat much faster than the average adult male due to the fact they have a larger body surface area in relation to their body mass. They also generally have much less body fat so it is vital to ensure on a regular basis, they are comfortable and using their layers correctly. Not for example; overheating and venting incorrectly, or venting too much and loosing heat too rapidly via convection.

Types of Heat Loss

We lose up to 65 per cent of our total heat through the combination shown above. Radiated body heat warms the cool air or moisture around our bodies, which is then stripped away by conduction or evaporation. Heat loss is greatest from exposed skin, particularly on areas of the body that have a large blood supply, such as the head and neck. The head alone accounts for 47% of the heat loss. 90% of the circulation in our hands is used to keep warm which is why our cold hands quickly lose dexterity. Therefore it is vitally important to reduce this danger by using high wicking base layers and covering up with hats, balaclavas, hoods and gloves.


The body heats the layer of air or moisture next to its surface. When this is taken away by cold air passing across the body, the wind or air caused by arm movement, convection takes place. This is substantially reduced by windproof clothes.


Conduction is heat which is transferred by direct contact between objects. The rate of body loss is determined by the conductivity of the material with which we are in contact. Pay attention to the surfaces you are in contact with (sitting on or leaning against) as you will be losing heat through these materials. To help reduce this process use cut up foam sleeping mats for sitting on at rest stops.


To change from a liquid to a gas, water requires energy. So when we sweat, or when moisture in our clothes evaporates, the fluid draws energy warmth from our body to make the transformation. In hot weather, we sweat and this can keep us cool, however in a cold climate this works against you. Water conducts heat away from your body 25 times faster than air. As we sweat in cold weather we replace the warm air trapped between our clothing layers with sweat. Then as the wet clothing dries on your body, heat is lost by evaporation. It is for this reason high wicking base and mid layers are important as they keep moisture off your skin.


We breathe in cold air, we warm it and then when we exhale our breath expels heat. This increases when in a cold atmosphere and is extreme in the dry cold artic, where more heat is lost as energy.


Every time we eat something your body is generating internal heat, which keeps us alive. We expend heat as we exercise and if we don’t replenish our internal supply we soon become exhausted. Exhaustion is a major contributor to hypothermia as well as creating a bad mental approach to our circumstances, anger, frustration and disappointment. Even if you are wearing the best gear, hypothermia is easily brought on by not eating and drinking regularly to stave off the effects of the cold.

The body heats the layer of air or moisture next to its surface. When this is taken away by cold air passing across the body, the wind or air caused by arm movement, convection takes place. This is substantially reduced by windproof clothes.