Skip to main content

Survival: Finding and Purifying Emergency Water

Bob Bahlmann is the executive director of the education nonprofit Explore the Outdoors and has written a series on wilderness survival.


Water Is One of the Essentials for Human Life

Whenever you venture into the wild, be sure to carry a good supply of water. If you find yourself lost without water, locating a safe source should become a priority.

You can lose as much as a gallon of water a day through sweating and urination. This water must be replaced if you plan to stay functional.

Finding water is critical, if not, dehydration will occur. The symptoms you could face include thirst, weakness, decreased mental capacity, nausea, no appetite, and severe headaches.

Some Tricks to Prevent Water Loss

  • rest
  • keep cool
  • stay in the shade
  • seek shelter

Don't wait until you run out of water to start looking for more. You can replace body fluids in more ways than just drinking water. Lots of foods contain water; good examples are fruit and vegetables. Avoid fatty foods, caffeinated beverages, and alcohol because they trigger digestion which uses up fluids.

How Long Can I Survive?

You Can SurviveWithout

Three Minutes


Three Hours


Three Days


Three Weeks


Surface Water Often Contains Impurities


In most parts of the world, surface water is not pure. Avoid water that is cloudy or might have been contaminated by dangerous chemicals such as pesticides, herbicides and fertilizers.

Even clear water can house bacteria and viruses that can cause very serious illnesses, such as diarrhea and dysentery. The fluid you lose through diarrhea and vomiting could be more than you would get from drinking contaminated water.

A common parasite found in even the most remote water sources is Giardia lamblia. It is found worldwide and all over the United States. Giardia causes diarrhea, which leads to dehydration.

How to Find Water

Frigid areas: Melt snow and ice. Do not eat snow or ice without melting! Eating snow and ice will reduce body temperature and could lead to more dehydration and hypothermia. Dirty snow or ice should be purified just like any other water source.

Rainwater: Rainwater is a great source of safe drinking water. Use the biggest container you can find to catch rainwater. A tarp or sheet of plastic can be used to collect even more water and funnel it into containers. Wet clothing can be wrung out for additional water.

Water at the beach: Here is how you can remove most of the salt from seawater. Dig a hole deep enough to allow water to seep in. This will filter some of the impurities as the water passes through the sand. Heat some rocks in a fire and drop the hot rocks into the water in the hole. Hold some cloth over the hole to absorb the steam. Now wring the water from the cloth.

Water in the desert: look for the following indicators to find water in the desert:

  • Valleys and low areas
  • The foot of concave banks of dry river beds
  • The bases of cliffs or rock outcrops.
  • The first depression behind the first sand dune of dry desert lakes.
  • Wherever you find damp surface sand
  • Wherever you find green vegetation

After you spot one of the locations mentioned above, dig holes deep enough to allow water to seep in. It's best to look for water in the desert at night, or at least during the cooler parts of the day. Working in the heat of the day could use up more water than you can replace with a limited water supply.

Cacti can be a source of water. Be careful to avoid the spines, cut off some of the inner cactus flesh and mash or squeeze the pulp. Don't eat the pulp, but place it in your mouth, suck out the juice and spit out the pulp.

Solar Stills

Stills draw moisture from the ground and plant material. You need special materials to build a still. Allow about 24 hours to collect 0.5 to 1 liter of water.

To make a belowground still, you need a digging tool, a container, a clear plastic sheet, a drinking tube, and a rock (see image below).


A Simple Filter Made From a Plastic Bottle

Cut off the bottom of the bottle, turn it over and fill it with progressively large filter material. Pour water into the filter and let it seep down and out the neck of the bottle into a container.

Cut off the bottom of the bottle, turn it over and fill it with progressively large filter material. Pour water into the filter and let it seep down and out the neck of the bottle into a container.

Water Purification

There are three ways to treat water: filtration, boiling and chemical purification. All natural water sources should be purified.


Filtering water doesn't purify it, but it reduces particles and sediment and makes the water taste better. Water can be filtered in many ways. Something as simple as pouring cloudy water through the fabric of a shirt or through a container filled with clean sand can remove most of the floating junk.

Adding a layer of charcoal from your fire can help remove some contaminants and also make the water taste better.

Filtering may not remove harmful bacteria from the water so one of the following purification steps should still be performed.


Boiling is the most certain way of killing all microorganisms. To purify water bring it to a rolling boil for at least three minutes. Boiling removes the oxygen from the water leaving it funny tasting. It is still safe to drink, but pouring it back and forth between clean containers will improve the taste.

Remember, boiling will NOT neutralize chemical pollutants.

Chemical Purification

There are many chemicals that can be used to purify water. Simple household bleach is one. Add five drops of bleach for every quart of water to be treated. Iodine and halazone are among other chemicals that can be used for water purification. Always follow the labels instructions on these and other treatment methods.

Purification Filters that Remove Micro-Organisms

There are microbial purification filters available that not only remove parasites like Giardia but also kill waterborne bacteria and viruses. Be sure to follow the directions that come with these filters.

The video demonstrates just one of these filters. This is included for an example only and is not an endorsement of the LifeStraw filter.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.