Jon's Quick Guide to Water in the Wilderness

This guide soley based on my personal experience and wilderness training at Cornell Outdoor education.  This by no means comprehensive.

Posted by Jonathan Bar on December 15, 2018
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Step 1: Finding sources of water

Remember the rule of 3s.  You can survive 3 minutes without oxygen, 3 hours without shelter (due to hypothermia risk), 3 days without water, and 3 weeks without food (provided you have water).  Therefore, water should be on everyone’s top priority list in a wilderness setting.  

On any wilderness expedition, I recommend that you carry at least 2 liters of water per person per day at an absolute minimum.  More if you anticipate staying overnight or will be in a hot, humid environment, or if you anticipate sources of water to be scarce.  It is prudent practice to identify sources of water on a map prior to heading out on any expedition.

If you are unsure of where to find water, a good bet is to descend.  Water from runoff and snowmelt generally flow downhill and coalesce into streams which become rivers and eventually lead to people.

Another good way to find water is to look for green plants.  Green plants need water.  You can also watch the animals.  They need to drink to and if you pay close attention, they will show you what you need to know.  In particular, pay attention to birds.  Flocks of birds tend to congregate over waterholes at sunrise and sunset.  

Ideal water sources are running clear water without animal feces or carcasses nearby.  However, in a pinch, just about any water source can be purified.

If you cannot find a stream or pond or other large body of water to resupply from, you will have to look for other sources.  

Note: If you have no water, DO NOT EAT.  Eating increases thirst and require more water.  If you must eat, high carbohydrate foods are best, such as a jolly rancher.  Avoid very starchy foods or meats.

The following sources of water from nature can be consumed without further purification:

Snow/ice melt (melt before drinking, DO NOT Melt in your mouth, as this consumes additional calories and lowers core temp).

Rainwater:  Be opportunistic and lazy!  Take what nature provides!  Look in rock crevices, holes in trees, place your shirt in and wring the water out if need be.  If the water looks like it has been standing for a long time, you should use one of the purification methods below.  

Water from vines and bamboo-the plants naturally filter the water from the ground which can be accessed by cutting into the plant.  The vines with the most water tend to be thicker and woody.  A neat trick is to poke a hold in the vine without severing it completely.  This will cause water to drip out which you can collect in a container.  The vine will eventually heal this hole but you can reopen it and repeat this process to have a continual source of fresh water.  

NOTE: DO NOT DRINK Water from any vine that tastes bitter.  It may have toxins from the plant in it.

Transpiration from Plants: All plants give off water from their leaves which you can capture by placing plastic bags over branches

Dew: easiest way to gather it is to wrap a shirt around your leg as you walk through tall dew covered grasses.  The water can then be wrung out of the shirt.

Coconut water: delicious and rehydrating, it contains electrolytes and saturated fatty acids (unusual for a plant).  The water from green coconuts is preferable as the water from brown coconuts can have a laxative effect.

Step 2: Purify the water

All other sources of water in the wilderness should be purified/disinfected.  The major risk is diarrheal illness from Giardia or cryptosporidium.  In general, the incubation period for these infections is 1-3 weeks so if you anticipate rescue before then, it may be worth the risk of consuming unpurified water in a true emergency. However, you still risk E coli, hepatitis, and other enteric pathogens depending on where you are in the world which have a much shorter incubation time. 

Conventional Methods of purification:

  1.  Boiling:  The heat from boiling the water kills just about all bacteria and parasites.  At Sea level, 1 minute is long enough.  Add an additional minute for every 1000ft above sea level you are.  If unsure, 10 minutes is safe everywhere.   This is my personal favorite method, as I usually carry my army issue canteen which comes with a metal cup to boil in.  If you do not have a metal container to boil in, you can make a wooden container out of bark (white pine works well for this), or using controlled burning techniques (lesson for another day) and then drop hot rocks in the water.  The rock boiling technique can actually be pretty quick and take under 5 minutes.  NOTE: DO NOT USE SEDIMENTARY ROCK for this as these rocks already have water in them and may explode if heated (I know from experience).  The main disadvantage of boiling is that it requires a head source such as fire or a portable stove.  It is also time consuming.  In in a wilderness medicine setting, boiling can be helpful to sterilize instruments as well.

  2. Chemical purification-There are many commercial products, most of which contain iodine or chlorine to disinfect water.  I’ve used these frequently on short backpacking trips.  They carry the advantage of being lightweight, work quickly (usually in 30 minutes or less depending on the product), and are very effective.  I’ve never gotten sick using iodine.  The disadvantage of these methods is that they expire, are probably unhealthy if used long term, and give the water a chloriny, pool water taste.  One trick when using iodine is to add a vitamin C tablet to the water after the disinfection process is completed.  I find that this helps take away some of the bad taste.  Follow the manufacturer’s instructions for use.

  3. Filters-There are a variety of commercial products out there for this. I’ve used several different ones.  I find that they are helpful for large groups because you can filter a large amount of water quickly.  They are also very effective. I’ve never gotten sick using water from filter.  They are also decently lightweight.  The main drawback is that they have a limited lifespan.

Emergency Methods of purification:

These methods are really only to be used when you have nothing else.

  1. Build a still.  This works on the principle that when water evaporates, only water evaporates (leaving the salt, bacteria, and just about everything else behind).  You start by digging a hole.  Then put the contaminated water in the hole and a container in the middle of the contaminated water.  You then cover the hole with a plastic sheet and place a rock in the middle.  The contaminated water will evaporate overtime, collect along the plastic sheet then drip towards the middle and fall down into your collection container.  The water in the collection container is now safe to drink.  One cool advantage of this technique is that you can purify salt water in this way.  The main disadvantage is that the process is painstakingly slow.  I’ve done this for over 24 hours and ended up with about a gulp of fresh water.  If you have the resources, you can boil the contaminated water to speed the process up, but you will need to weigh whether or not the energy expended to make such a system is worth it in your given situation.

  2. Make a filter:  The way I’ve done this before is to tie off a pant leg (any cloth back will work though and then add several alternating layers of filtering material such as sand, followed by grass, more cloth, and charcoal.  The more layers the better.  Then pour the contaminated water through it.  This will filter out large debris, dirt, feces from very contaminated water, but will not clear microorganisms.  The resultant water should then be purified using another method.  Alternatively, you can let very muddy water sit for 12 hours.  This will allow the debris to settle out and you can pour the water out from the top.  This water should also still be purified with another method if possible.