I am on a bit of a intensive study session at the minute. My topic of choice is water procurement and purification.
Imagine you are out on a hike in warm weather. You have a full water bottle, more than enough for the day, and are well hydrated. You feel strong and decide to head to a view point you heard about a few miles off the trail. You don't have a map but you know the area well.
The climb to the view point is brutal and you are sweating buckets. You reach a place which looks like what was described and stop for a drink only to discover that your bag was not closed properly and your water bottle has dropped out. Oops.
Anyway you feel thirsty now and are still sweating and breathing heavily. Dehydration is now well under way!
Oh well, back down the trail keeping your eyes open for the water bottle. Your head starts to hurt a bit and you feel much more tired than you did before. Concentration is ebbing a bit and you begin to question if you are on the right trail.
You know you need to drink something but you keep going because you know that you have water in the car. A few hours later you realise that you did take the wrong path but know the right way now.
Your headache is pounding, your eyes and mouth are dry, you feel terrible.
The sun has gone down and you start to feel really cold. Water is an important part of heat generation. You dont have the energy to keep up a brisk pace and stop by a small stream.
You try to remember the rules about wilderness water sources. Its hard to think straight when your head hurts so much.
The water looks very clean and you can see the bottom. You lie down on your belly and drink deeply. You instantly feel better. It is pitch black now and you get out your warm layers and wrap up warm. It will be light in a few hours and you can find the car and get home. You are not expected back until tomorrow anyway and it will be a bit of an adventure to tell your friends about. You drift off to sleep.
Upstream the dead deer carcass continues to decompose in the stream. A few rodents are gnawing at it and save some time by defacating and urinating at the same time. This lovely cocktail flows down stream.
The next morning you wake up with a bit of a stomache cramp which slowly gets stronger. You are seating profusly. you feel a very sudden urgent need to poo and run begind a tree just in time to shoot a line of diarrea out all over the ground. Then you vomit.
You have been infected with a waterborne nasty. The short time it took to produce symptoms suggests you drank a lot of it.
You lie in pain waiting for the next dose of diaorrhea steadily losing what little water is left in your body.
Basically you are in seriously deep shit both metaphoricaly and physically.
There is lots of confusing and contradictory information on water collection.
If water appears visually clean it is often said that fast moving water is best and slow moving water is bad.
This is not correct.
Nature has a number of ways to purify water before we even get near it.
Solar radiation is a powerfull force for purification of water. In fast moving water this force never really gets a chance to work as the water is constantly moving and is churned up. In slow moving or still water the sun can penetrate the water for a few inches and interfere with the microorganisms biological processes
Fast moving water stirs everything up and holds onto anything it encounters carrying it down stream. Contaminants dont get a chance to settle and end up in your water bottle.
So slow with flow is the way to go as a first step.