Water

I discuss water elsewhere. But to reiterate, the average person loses 2-3 liters of water a day by respiration alone.

The onset and effects of dehydration are:

Dehydration levels and effects on the body. Loss in liters is based on a body weight of 70kg. Number of days is based on a loss of 2 liters per day
Fluid loss (%) Fluid loss (liters) Symptoms Days (maximum)
1-5%
0.7-3.5
Thirst, discomfort, appetite loss, flushed skin, irritability, sleeplessness, nausea
1-2
6-10%
4.2-7
Dizziness, headache, breathing difficulty, no saliva, slurred speech, unable to walk
2-4
11-20%
7.7-14
Delirium, swollen tongue, swallow difficulties, vision blurring, numb and shrivelled skin
4-7
Serious trouble!
Body and brain start to shut down
Pray for rain

If you don't have an assured water supply and you simply don't know where the next resupply is coming from, rationing must be a first priority. In a survival situation aim to make 1 liter of water last about 4 days at 1/4 liter per day for 3 days. The last 1/4 liter is then made to last 3 days at about 80 ml per day. This 80 ml should be taken over 2 doses. Say, midday and night. This is a modest mouthful.

Needless to say, this is an extreme situation and even a glancing reference to the dehydration table above will illustrate how much the limits of water deficit are being pushed. You will be only be slowing the entry in the second and third stages of dehydration, and even then not by much.

If you are fortunate enough to have access to water (I envy those hiking in lovely wet boreal forests!), count yourself lucky. I have been in situations in which finding water is a very serious issue. How can we find water?

Collection

This may seem obvious, but don't waste any opportunity to collect water. If it rains, you would be silly not to place containers at strategic points under your shelter. And when your containers are full, bomb-up (ie. drink any excess). Water running down the sides of hills and rocks can be easily channelled into a water bottle using a stick or similar as a conduit for water to run along. If you have an enclosed tent, lick the inside in the morning. You're not getting new water, just reclaiming some you lost overnight. Oh, and for those who got their survival information pre-WWII, sucking a stone doesn't give you water. It just takes it out of your salivary glands.

Gravity is your friend - dig!

Water, as with everything except Hollywood Stars, Supermodels, and famous Musicians, obey the law of gravity.Water in creek bed What water did before Newton invented gravity is a mystery to me. This is where the Zen of observation I always harp on about comes into play.
Dry creek beds and remnant pools or depressions in the creek bed are good places to start digging for water. The color and wetness of the soil will let you know how close you are getting. Plants do better near water, so try areas in the creek bed where the plant life is flourishing. Look at the banks of the creekline for mini re-entrants which indicate where water drains into the creek bed. Look for water-thirsty vegetation such as mosses. These are good indicators that underground pools are close to the surface.

Water will also travel underground. Occasionally there can be hollow channels like underground rivers, but more usually it is percolating through porous soil layers. A hole dug through these layers will fill with water. It should also be noted this applies to seashore dunes as well. A hole dug behind the line of dunes will contain fresh, not salt water. The hole of course should be above high tide level, but below the landward slope. That gravity thing again.

There are some places in the world where this may not work as nicely as the books say they do. I have been in parts of various Australian deserts where you could have a backhoe and still not find water by digging. This is a serious situation, because to find water you will have to move. To move, you need water. Catch 22. In these places however, I have usually got at least a little bit from condensation form the limited amount of vegetation there is. In other places the water table may be excessively salty so you can't drink it directly, but this can be dealt with by a solar still.

Condensation

I mentioned in the introduction to the Survival Transpiration water collection section that I try all methods that the books suggest. If there is moisture in something, condensation methods work to get it out. The premise is very simple - collect evaporated moisture. The inside of your tent gets wet because your body loses metabolic water through breath and sweat. If you seal a plastic bag around a bush or branch, you can collect the metabolic water breathed out from that plants respiration. The water will be relatively free from salts and oils, which do not evaporate. However avoid doing this with toxic vegetation. While the metabolic water itself is free of any nasties, contamination by rubbing against the leaves or toxic oils leaching out into the bag can contaminate the collected fluid. You will not get a lot of water, but enough to add to a base ration. From experience, this is a pretty inefficient use of a perfectly good garbage bag.
A more useful variant on the condensation theme is a solar still.Solar still These are great. They are the 'new duct tape'. Well, nearly. The basic principle is to dig a hole, say 1m across by 50cm deep; cover it with plastic such as a garbage bag (which you should have in your pack to waterproof gear) or a tarpaulin, secured at the sides so it doesn't fall in; place some stones in the centre to make an inverted cone; and collect the condensed water in a cup. I generally use a garbage bag and I put a hole in the bottom of the cone to collect any dew or rain as well.
We can of course be smart about this solar still malarkey. It makes sense to dig our hole in a place where the soil is likely to be damp. Remember the creek bed mentioned above? Perfect. We know that leaves and other vegetation give off transpiration water, so topping up the hole with vegetation will provide another water source. Caution: Don't let the vegetation touch the plastic or else the fluid will run down the leaves and not into your cup as intended. What else can we throw into the hole I wonder? Urine and, if near the ocean, salt water can be poured into the hole. Salts are left behind from evaporation, which is how table salt is made. From experience, urine can give a bit of an ammonia smell to the water, however the salts contained in urine are left behind. In case there are people in the world who haven't heard - NEVER drink urine or sea water! And, for those who are still pondering Baldrick's question of Blackadder, whether you drink your own or each other's urine is irrelevant. Absorption of water into your body relies on salt gradients. If the fluid you're drinking has higher salt content than your body, water will actually leave your cells. You will be dehydrating yourself further.
A still of this size could provide 0.5 liters over 24 hours. Better than a kick in the ass!
Condensation water distillation You can carry this to the extreme by using a fire to speed up the process and distill the contaminated water. Basically boil the water, collect the steam, and let it drip back into a water container. Now while the ideal diagram indicates you need a convenient bit of hose pipe, it's actually quite easy to jury-rig a still. What do we have that normally collects condensation? Our shelter and our handy stash of garbage bags. Rig these as a tent over the boiling water (don't burn them!), use them as the condensation surface, and channel the water to a container. It's not as efficient, but still (Ha! Geddit?) works pretty well.

Plants and animals

A staple method of survival manuals is how to get fluids from plants directly, such as from tree roots. The basic principle is to cut and stack plant roots, which do indeed contain fluid, and collect the draining fluid. Richard Graves in Australian bushcraft cites 100ml of fluid per meter of root, with the caution that the sap contains sugars as well, and milky sap is generally toxic. I've had next to no success with this method in arid regions. The roots are too dry and heal too quickly.Tree root water collection Cup-shaped plants such as bromeliads and some palms indeed can hold small amounts of water where the branch or frond intersects the trunk. Ants and other insects will also lead to these sources. Bamboo can also contain water. My experience with these sources has been that they are generally found in wet places anyway, so I've found them of limited utility compared to finding free water or condensation methods. Other suggestions have included chewing/sucking vines, roots, palms, and cacti. This does require local knowledge, and while I know many species from a few geographic regions it would be best for the reader to find out about their own species. Generically, I don't recommend these methods. First, some of these plants can be toxic. If they don't kill you, they can make you sick or give you diarrhea and hence increase water loss. Second, some of these fluids may be too salty or sugar rich. As an aside, this includes the old 'suck fish eyes' and 'fish spinal fluid' water sources. I would prefer to condense and drink the water the fish was living in, rather than the salt-concentrated eyes. Not because I'm squeamish (I'm not!) it's just more sensible to bypass the middleman.
Animals can lead you to water. Grazing animals such as deer and goats need free water. Don't bother chasing individuals around, rather look for the tracks. Water treks are regular events which will have strong trails. I personally don't really get much more information from animal tracks than I would by just examining the terrain and vegetation.

Ice and snow

Rather paradoxically, icy and snowy areas high above the snowline can be quite dry. The air can be dry, and free water is locked away. However, heating ice will obviously yield water, but at the cost of fuel. Snow is primarily air bubbles, which is why it is a good insulator, so focus on melting ice or very densely packed snow. Of course it is usually easier to drop below the snowline where there will be no shortage of water.

Filtration and treatment

In a survival situation you can't be too fussy, however you should thinkWater purification tablets about how you treat water from different sources. I've said it before and I'll say it again - condensation is great. The only source of pathogens will be from the plastic and your container. If you have taken water from sources in which there are a lot of livestock, then you have to be careful. Mud can be removed by filtering through a sock or similar, but this doesn't remove pathogens. Ideally water should be boiled, but fuel may become limiting. Purifying tablets should be used when possible. Stomach infections can be debilitating and you can lose vast quantities of fluid from both ends. On the bright side - these can go back into the bottom (so to speak) of the solar still.