Water supply on hiking trips: the guide

Managing your water supply while hiking can quickly become a challenge on long trips, in full autonomy or with few resupply points along the route. Hydration is essential for any hiker — it's something that must not be overlooked and should be carefully considered in advance. You also need to be fully aware of the risks of contamination from water found in nature, and of course have appropriate means with you to make that water safe to drink. Here is a comprehensive guide to help you ensure you're drinking safe water wherever you are and whatever conditions you face. 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 the contaminants found in water are invisible to the naked eye. So in all cases, treat it as unfit for consumption and purify it to make it safe for your body!

Water supply while hiking: where to collect water?

While any water you find in nature should be considered impure, you should still select it based on a few simple common-sense criteria that will help you avoid the most serious problems:

• Avoid stagnant water sources entirely: harmful micro-organisms and viruses thrive there in whole colonies, and no method will be completely effective at eliminating them entirely.
• Choose the clearest water possible: it's not a guarantee of perfection, 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 prevents a large number of contaminations.

Once your flask is full, if the water still contains visible particles (sand, gravel, mud…), let it settle until the suspended particles sink to the bottom. 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 and purify.

What contaminants might you encounter in water collected from nature?

There are broadly 3 main families of contaminants found in water: biological, chemical and radiological. Biological contaminants: In natural environments, these are arguably the most common. 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.
• Certain waters may also contain viruses (hepatitis A or E, Legionnaires' disease, dengue fever…) ready to infect any passing human.

Chemical contaminants: Found downstream of human activity (industry, agriculture…) and also from airborne contamination through chemically laden rainfall or accidental pollution, so-called chemical contaminants such as pesticides, nitrates or heavy metals can be present in water collected in natural environments. In mountainous areas, water can also be overloaded with minerals (even naturally occurring ones) and therefore toxic to the human body if consumed repeatedly. Radiological contaminants: These are rarer but should not be overlooked. Obviously, areas such as Chernobyl or Fukushima are likely to have high levels of radiological contaminants in natural water sources. But traces of varying significance can be found elsewhere too. The risks associated with water consumption vary from country to country. It is essential to research the sanitary conditions and water-related hazards in the country you are visiting. It is important to understand that ingesting chemically and/or radiologically contaminated water is certainly highly toxic, but in most cases only when consumed regularly. Occasional consumption is less serious. However, drinking biologically contaminated water (with bacteria, protozoa or viruses) presents an immediate risk, even danger. A single sip can be enough to make you ill… Abroad, be wary of a local telling you that water is safe to drink. It can happen that local populations 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 while hiking: water decontamination methods

One of the most effective methods to decontaminate water is simply to boil it. The vast majority of biological contaminants in water are killed after one minute at 100°C. Allow approximately five minutes at 85°C at around 4,000 metres altitude, and 30 minutes at 70°C at 8,000 metres altitude! This time-tested method is safe and eliminates viruses and pathogenic micro-organisms present in water. It has the advantage of being simple and highly effective against biological contaminants; however, it is very time-consuming, uses a lot of fuel, and is ineffective against solid particles and chemical pollutants. Another point not to overlook: apart from making soup or a warm freeze-dried meal, you'll need to wait before drinking as the water will be far too hot. Boiling can also sometimes alter the taste of the water. Filtering water You can very easily filter water with a simple coffee filter or a specialised filter. Most filters available today have pores ranging in size from 0.1 to 0.3 microns (= one millionth of a metre). The smaller the pores, the more effective the filter against particles and micro-organisms — but the longer the filtration process will take. It should be noted that a filter will be completely ineffective against viruses. We'll cover how to deal with them further on. 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 capturing certain chemical components such as chlorine, iodine, herbicides, pesticides and some heavy metals. Another advantage of the carbon core is that it removes the unpleasant chlorinated and iodine taste from water by trapping these substances.
• Fibreglass filter: retention power and filtration quality equal to the ceramic filter, but a significantly shorter lifespan and a somewhat delicate fragility.

Most filtration solutions are fitted with a pump that speeds up water flow but can sometimes require a little physical effort. Some work by gravity or suction but are slower. Many filters are fitted with 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 affordable price make them a must-have for any hiker. 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 clarity of the water. The water often takes on a rather distinctive 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. Common 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 well suited for individual consumption. The UV pen This 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: quick to use and reliable. The UV pen, however, requires batteries to operate and is relatively expensive and quite fragile. Unfortunately, no system is perfect or 100% effective regardless of location. However, bear in mind that any water you consume should at minimum be filtered and then purified. If you choose a clean source with reasonably clear water, filter it through a proper filter, and purify it with a tablet, you eliminate 99% of the risks. While it is recommended to filter and 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, avoid exposing open wounds and cuts to water, and avoid submerging your head. Be particularly vigilant when washing in a river, where even the smallest cut could become infected. Your water supply while hiking will be safe if you follow our advice and equip yourself with the necessary tools to ensure clean water. There's no need to be overly anxious about the risks — simply take the matter seriously and with care. Filtering and purifying your water will prevent the vast majority of contamination issues, and you can focus on enjoying your trek or hike!