permaculture

["Lawrence F. London, Jr." <venaurafarm@bellsouth.net>]

On 11/19/2011 5:14 AM, Dieter Brand wrote:
> 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.

Shade it to keep it from heating up and put plastic over it to prevent 
evaporation

alternate: run the water into a small pool or pools, containers, ponds 
where you have many aquatic plants growing including duckweed which will 
completely cover the water surface, shading it and preventing much 
evaporation - you will get nutrients from the decaying plant material - 
you might get algae growing too but it will need nutrients to survive 
and the duckweed will also feed on those nutrients and outcompete the 
algae to dominate the water surface - introduce fish, snails and other 
organisms that thrive and coexist with other inhabitants of a freshwater 
environment. As for quality of plant nutrients in the output of the 
impoundment this may be better than water from algae culture.