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I'm toying with the idea of collecting water from tree leaf transpiration, while hiking:

enter image description here

Obviously, vegetation with larger leaf surface area (and certain types) would be better than others.

But is it useless to try and collect water from trees during the night? Do trees not transpire as near as much during the night as the day - or maybe not at all?

Obviously if you are thru-hiking, daytime tree water collecting is simply not possible (as a principal water source at least), it could only possibly be done at night time.

So how practical might this idea be? Perhaps it is more practical in certain climates but not others?

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    Most places you would find such trees, you would also find more than sufficient water as to make the exercise pointless.
    – Michael Hampton
    Commented Aug 21, 2014 at 15:36
  • Well, what about environments in which the relevant trees are actually using established / deep taproots to gather their water from the water table or a fairly deep water aquifer, thus being less practical for you to gather the water source conveniently yourself? Not saying that it's still the best solution in those situations, just that maybe your assessment isn't as common as you suggest...
    – user2189
    Commented Aug 22, 2014 at 0:53

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Tree's generate water as part of the respiration process (not to be confused with photosynthesis which is different). This happens at night and day.

enter image description here

This is relatively static day or night. Photosynthesis alters dependant on sunlight, respiration (being the process of producing energy) does not. Respiration will alter dependant on the time of year, i.e. in winter a tree may be dormant with no leaves, etc. and respiration almost stops.

You're not going to be able to generate anywhere near enough water using this method, regardless of the time of day. This is a useful survival method but that's it. do not rely on it as a source of water.

The trap you show above is likely to produce a few ml of water per day regardless of climate. You're likely going to need several litres of water per day.

I couldn't find any exact figures on the amount of water you're going to get but this wikipedia article describes a condensation trap much larger than the one you describe that yields very low volumes of water:

Condensation traps are not in themselves a sustainable source of water; they are sources for extending or supplementing existing water sources or supplies, and should not be relied on to provide a person's daily requirement for water, since a trap measuring 16" in diameter by 12" deep will only yield around 100 to 150 ml per day.

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    I seem to remember a video by Ray Mears where he does this (with a bigger bag) in Australia and gets about a glass full, so I think you're understating it. Essentially, if you do this to enough trees, you might kind of sustain yourself (assuming the trees aren't damaged by the process, which they might). This seems to be it: youtube.com/watch?v=JXjW5Veb5Rk I do agree with your point, though.
    – Zubo
    Commented Jul 21, 2016 at 14:50
  • Yes I think I was thinking of that when I wrote this
    – user2766
    Commented Jul 21, 2016 at 14:55

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