Water supply on hiking trips: the guide

Managing your water supply on hiking trips can quickly become problematic over long distances, in full autonomy or with few resupply points along the route. Since hydration is essential for hikers, this is a point not to be overlooked and one to study carefully in advance. You also need to be fully aware of the risks of contamination from water found in nature and, of course, have the appropriate means with you to make that water drinkable. Here is a comprehensive guide to help you ensure you drink safe water wherever you are and whatever conditions you find yourself in. Not all water found in nature is safe to drink, far from it. Even the clearest water can have been contaminated upstream. Be aware that 99% of contaminating agents found in water are invisible to the naked eye. So in every case, treat it as unfit for consumption and treat it to make it safe for your body!

Water supply on hiking trips: where to collect water?

If the water you find in nature must be considered impure, you should nonetheless select it according to a few simple, common-sense criteria that will help you avoid the most serious problems:

• Avoid any source of stagnant water entirely: harmful micro-organisms and viruses proliferate there in entire colonies and no method will be completely effective in eliminating them entirely.
• Choose the clearest water possible: this is not a guarantee of perfect purity, but it greatly reduces the need for filtration and indicates a degree of reliability.
• Always collect water upstream (above) and as far as possible from human or farming activity: this avoids a large number of contaminations.

Once your bottle is full, if the water still contains visible particles (sand, gravel, mud…), leave it to settle until the suspended particles sink to the bottom of the container. You can then pre-filter the water through a scarf, a t-shirt, or a coffee filter… The more particles the water contains, the harder it will be to filter/purify.

What contaminants might you encounter in water collected in nature?

There are broadly 3 main families of contaminants found in water: biological, chemical and radiological contaminants. Biological contaminants: In natural environments, these are a priori the most numerous. There are several different types.

• Protozoan parasites: these are micro-organisms often of animal or human origin, transmitted via the faecal-oral route.
• Salmonella, Coliform or Escherichia coli (E. coli) bacteria are present in water that has been contaminated upstream by animal or human waste.
• Some waters may also contain viruses (hepatitis A or E, Legionnaires' disease, dengue…) ready to attack any passing human.

Chemical contaminants: Found downstream of human activity (industry, agriculture…) but also in the event of aerial contamination from rain laden with chemicals or accidental pollution, so-called chemical contaminants such as pesticides, nitrates or heavy metals may be present in water collected in natural environments. In the mountains, water can also be overloaded with minerals (even natural ones) and therefore be toxic to the human body if consumed repeatedly. Radiological contaminants: They are rarer but not to be overlooked. Obviously, areas such as Chernobyl or Fukushima must have a high abundance of radiological contaminants in water found in natural environments. But it is not uncommon to find traces of varying levels elsewhere. The risks associated with water consumption naturally vary from country to country. It is essential to find out about sanitary conditions and the dangers related to water in the country you are visiting. It is important to understand that ingesting chemically and/or radiologically contaminated water is certainly highly toxic, but very often only in the case of regular ingestion. Occasional consumption is less serious. On the other hand, drinking biologically contaminated water (with bacteria, protozoa or viruses) presents an immediate risk, or even danger. A single sip can be enough to make you ill… Abroad, be wary of advice from a local who tells you that water is safe to drink. Some populations may have developed a tolerance to water that would make you ill after just one bottle, because your body is not protected against the contaminants it contains!

Water supply on hiking trips: water decontamination methods

One of the most effective methods for decontaminating water is simply to boil it. The vast majority of biological contaminants in water are killed after one minute at 100°C. You should allow around five minutes in water at 85°C at approximately 4,000 metres altitude, and 30 minutes in water at 70°C at 8,000 metres altitude! This tried-and-tested method is safe and eliminates the viruses and pathogenic micro-organisms that water contains. The process has the advantage of being simple and highly effective against biological contaminants; however, it is time-consuming, uses a lot of fuel, and is ineffective against solid particles and chemical pollutants. Another aspect not to be overlooked: apart from making soup or a warm freeze-dried meal, you will need to wait before drinking your water as it will be far too hot. Furthermore, boiling can sometimes alter the taste of the water. Filter water You can very easily filter water with a simple coffee filter or a specialist filter. The majority of filters available today have pores ranging in size from 0.1 to 0.3 microns (= 1 millionth of a metre). The smaller the filter pores, the more effective the filter will be against particles and micro-organisms, but the longer the filtration process will take. It should be noted, however, that a filter will be completely ineffective against viruses. We will look at how to deal with them later. Filters available on the market differ according to their material:

• Ceramic filter: the pores of ceramic filters generally measure between 0.1 and 0.15 microns, making it a highly effective filter. The qualities of the ceramic filter and its long lifespan make it a very popular choice among hikers and outdoor enthusiasts.
• Ceramic filter with carbon core: the addition of a carbon core to the traditional ceramic filter increases its filtration capacity by retaining certain chemical components such as chlorine, iodine, herbicides, pesticides and certain heavy metals. Another advantage of the carbon core is that it removes the unpleasant chlorine and iodine taste from the water by capturing these substances.
• Fibreglass filter: a retention capacity and filtration quality equal to that of a ceramic filter, but with a much shorter lifespan and a somewhat delicate fragility.

Most filtration solutions are fitted with a pump that speeds up the water flow but sometimes requires a little physical effort. Some work by gravity or suction but are slower. Many filters are mounted on a pipette or connected directly to a bottle or flask. Here again, the finer the pores, the harder and slower the suction will be. Purification tablets: Water purification tablets are practical, effective and easy to use. Their lightweight nature and accessible price make them a must for hikers. Whatever the brand, they effectively eliminate bacteria and viruses and are now widely used across all outdoor activities. The purification process is, however, quite lengthy: between 30 minutes and 2 hours depending on the type of tablet and the cleanliness of the water. The water often takes on a rather unusual flavour (though you can correct this by adding an energy gel, a mint tablet or a tea bag). Unfortunately, tablets are relatively ineffective against solid particles and chemical pollutants. Classic disinfectants: Chlorine, bleach or iodine can also be used to purify water; however, these products require precise dosing and must act for at least 30 minutes to be effective without being toxic. They are mainly used to purify large volumes of water (jerrycans, camping-car tanks…) but are not particularly well suited to individual consumption. The UV pen It is the equivalent of a pen that you dip into a container of water to neutralise pathogenic micro-organisms. The system is very lightweight and compact: it is quick to use and reliable. The UV pen does, however, require batteries to operate and is, despite everything, quite expensive and very fragile. Unfortunately, no system is perfect or 100% effective everywhere. That said, it is worth remembering that any water you consume should be filtered and then purified as a minimum. If you choose a clean water source with fairly clear water, filter it with a proper filter and purify it with a tablet, you eliminate 99% of the risks. While it is recommended to filter/purify the water you drink, it is equally important to use safe water for cooking or brushing your teeth, for example. When washing and bathing, take care not to let your open wounds and cuts come into contact with water, and avoid submerging your head. You should be especially vigilant when washing in a river, where even the smallest wound can become infected. Your water supply on hiking trips will be safe if you follow our advice and equip yourself with the necessary tools to ensure clean water. There is no need to be overly anxious about the possible risks — simply take the matter seriously and with caution. Filtering and purifying your water will prevent the vast majority of contamination problems, allowing you to focus on enjoying your trek or hike!