permaculture

[Dieter Brand <diebrand@yahoo.com>]

Hi, I have a request which may be a little strange and perhaps there is no 
real answer to it.  Anyways, it does occupy my mind:

I live in a semi-arid region with a prolonged and severe dry season.  So, 
every drop of water I can save counts.  I have a spring up in the mountain 
and several water holes which together provide just enough water to irrigate 
about half an acre during the dry season, if I use it very sparingly.

I recently hit on the idea of letting the irrigation water run through open 
channels or a series of containers where, under the light of day, algae would 
form in the water.  I do believe that these algae would have a beneficial 
effect on the irrigated soil.

The problem is that I don’t want to expose the water directly to the sun 
since I don’t want to risk that any of it evaporates.  What would be the best 
way to construct such waterways?  Should I cover them with some sort of 
semi-transparent shading cloth that is permeable to air?  Or should I use 
transparent glass or plastic that isn’t permeable to air?  I don’t want the 
water to heat up under the glass or plastic.  But if I use a shading cloth, 
I’m not sure that none of it will evaporate.  As I said, I can’t afford to 
loose a single drop.

Dieter