How to Find Water
After you've dealt with any immediate safety issues and have taken care of building an emergency survival shelter, one of your next immediate concerns should be procuring water. After all, you can survive for many days and even weeks without food, but you'll die after a few days without water. Finding water in an emergency situation often just requires a little creativity.
Collect Rainwater and Dew
You'll need a container of some sort. Anything will do such as a bowl, plate, helmet, even plastic shaped appropriately. In dry environments, condensation forms on surfaces overnight so set up a system to collect this water with a tarp. To collect dew, which forms in the early morning, tie clothing to your ankles and walk through grass and other foliage. The dew will soak in to the clothing which you can wring out later.
Look for Lush Forests
If your immediate location is dry and barren, but green trees lie off in the distance, consider heading towards them. Plants need water just like people do. The trick is not to walk so far that you expend too much of your energy.
Look for Bird Droppings
I bet you're thinking that I'm going to suggest you consume bird droppings. Fear not. The presence of bird droppings can indicate a source of water as they often congregated around cracks where water collects. If you find such a crack, shove a cloth in to it soak up the water.
If you're lucky enough to be in an area where banana trees grow (say a deserted island), you'll be able to get water from them. You'll need to cut it down and then scoop out the center of the stump. The roots will continue to pull water out of the ground which will collect in the stump. The first batch will be bitter, but subsequent batches will taste fine. This technique will last for 4 days.
Remember that these suggestions are for emergency use only. Every source of water may be contaminated with bacteria and viruses that can make you quite sick. Rainwater collected in a clean container is the safest. And generally speaking, moving water (e.g. river) is safer than standing water (e.g. pond).
Also remember that saltwater is not safe to drink because of the salt. Consuming salt water, or sea water, causes water to be drawn out of the cells and into the blood plasma. This leads to cellular dehydration which is a very dangerous condition that can cause death. However, in extreme situations you can drink less than 32 ounces of seawater per day and keep the effects to a minimum.
The Worst Case Scenario Survival Handbook – Travel by Joshua Piven and David Borgenicht