[Nathan Zachary]

The suns UV rays will destroy the poly sheets in a short time, the atmospheric dust settling on the poly will block the sunlight and kill the plants which are very sensitive to variations of sunlight. In the desert, rare but sudden and heavy rainfalls will also destroy the system.

It's a nifty method for gathering some drinking water in a survival situation, if you happen to have a sheet of poly, but for a permanent long term water supply, forget it.

Dig that well, and/or store rain and seasonal stream water when you can. Those are still the best tried and true methods for what you are doing.

[I see my hands]

"The suns UV rays will destroy the poly sheets in a short time, the atmospheric dust settling on the poly will block the sunlight and kill the plants which are very sensitive to variations of sunlight. In the desert, rare but sudden and heavy rainfalls will also destroy the system"

Who said anything about poly? Why do I care about plants? How will a sudden hard rain destroy the system?

What solutions to the problems that you cite can you come up with? It’s not just chaotic mother nature at work. We have brains.