Managing your water supply on a hiking trip can quickly become a real challenge over long distances, in full self-sufficiency or with few resupply points along the route. Since hydration is essential for any walker, this is not something to overlook — it deserves careful advance planning. You also need to be fully aware of the risks of contamination from water found in the wild, and of course carry the appropriate means to make that water safe to drink. Here is a comprehensive guide to help you ensure you are always drinking clean 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-looking water may have been contaminated upstream. Be aware that 99% of the contaminating agents found in water are invisible to the naked eye. So in all cases, treat it as unfit for consumption and process it to make it safe for your body!
Water supply on a hiking trip: where to collect water?
Although water found in nature should always be treated as impure, you should still 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 at all costs: harmful micro-organisms and viruses thrive there in their millions, and no method will be completely effective at eliminating them entirely.
- Choose the clearest water possible: it's no guarantee of perfect purity, but it greatly reduces the need for filtration and is a sign of some degree of reliability.
- Always collect water upstream (above) and as far as possible from human activity or livestock farming — this avoids a good number of contaminations.
Once your water bottle is full, if the water still contains visible particles (sand, grit, mud…), let it settle so that 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 and purify.
What contaminants might you encounter in water collected in the wild?
There are broadly 3 main families of contaminants found in water: biological, chemical and radiological.
Biological contaminants:
In natural environments, these are a priori the most common. Several different types exist.
- 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 water may also contain viruses (hepatitis A or E, Legionnaires' disease, dengue fever…) ready to strike any human being who passes through.
Chemical contaminants:
Found downstream of human activity (industry, agriculture…) but also in cases of airborne contamination from rain laden with chemical products or accidental pollution, so-called chemical contaminants such as pesticides, nitrates and heavy metals may be present in water collected in natural environments. In mountain areas, water can also be overly rich in minerals (even natural ones) and therefore 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 are likely to have a high concentration of radiological contaminants in natural water sources. But traces — sometimes significant — can be found elsewhere too.
The risks associated with drinking water vary considerably from country to country. It is essential to research the sanitary conditions and water-related hazards in the country you are travelling to.
It should be noted that ingesting chemically and/or radiologically contaminated water is certainly highly toxic, but in most cases only through regular consumption. A one-off intake is less serious. However, consuming 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 a local telling you that a water source is safe to drink. It can happen that local populations have built up a tolerance to water that would make you ill after just a single bottle — your body simply isn't protected against the contaminants it contains.
Water supply on a hiking trip: 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. 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!
This age-old method is reliable and eliminates viruses and pathogenic micro-organisms from 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 aspect not to be overlooked: aside from making soup or a hot freeze-dried meal, you'll need to wait before drinking, as the water will be far too hot. Additionally, boiling sometimes affects the taste of the water.
Filtering 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 (= one millionth of a metre). The smaller the filter pores, the more effective the filter 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 further on at how to tackle them.
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 trapping certain chemical compounds such as chlorine, iodine, herbicides, pesticides and certain heavy metals. Another advantage of the carbon core is that it eliminates the unpleasant chlorine and iodine taste from the water by capturing these substances.
- Glass fibre filter: retention capacity and filtration quality equal to a ceramic filter, but a much shorter lifespan and a fragility that makes it rather delicate to handle.
Most filtration solutions come with a pump that speeds up the flow of water but sometimes requires 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. 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 light weight and affordable price make them a must 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 unusual flavour (though you can correct this by adding an energy gel, a mint tablet or a tea bag). Unfortunately, tablets are largely 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 be left to act for at least 30 minutes to be effective without being toxic. They are mainly used to purify large volumes of water (jerrycans, camping reservoirs…) and are not particularly well suited to individual use.
The UV pen
It works like a pen that you dip into the water container to neutralise pathogenic micro-organisms. The device is very light and compact: 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 and 100% effective regardless of where you are. That said, remember that any water you consume should at a minimum be filtered and then purified. If you choose a clean water source with reasonably clear water, filter it through a proper filter and purify it with a tablet, you eliminate 99% of the risk.
While it is recommended to filter and purify the water you drink, it is equally important to use clean water for cooking or brushing your teeth, for example. When washing or bathing, take care not to let any open wounds or cuts come into contact with the water, and avoid submerging your head. You should be particularly careful when washing in a river, where even the smallest wound can become infected.
Your water supply on a hiking trip will be safe if you follow our advice and equip yourself with the right tools to ensure clean water. There's no need to be overly anxious about the possible risks — simply take the issue seriously and proceed with care. Filtering and purifying your water will prevent the vast majority of contamination problems, and you'll be free to focus on the enjoyment of your trek or your hike!
