permaculture

[Jay Woods <woodsjay@cox.net>]

A concept that I've used in the past is an artificially perched water table. 
An example was to build a dam in a hard rock canyon with a dirt floor that 
only came a few inches above the soil surface. Well water from behind the dam 
was used for irrigation on the higher slopes as well as house water. The dam 
was slowly heightened to trap any soil that was washed down the canyon during 
storms. With this approach there was very little free water surface to 
evaporate and that only in the spring when the evaporation rate was slow.

On Wednesday 27 August 2008 03:27:17 pm Dieter Brand wrote:
> I live in the South of Portugal.
> Rainfall May through September:  0 inches.
> This is not a drought it is the regular dry season.
> A drought is when the winter rains also fail, which happens on everage
> twice every 14 years. 
> Most people around here have artificial lakes.  A bulldozer will close a
> small valley with a dam and then compact the soil.  In some places the soil
> holds the water well, in other places the lake bottom leaks so much that it
> runs dry before the summer is over even without using any water for
> irrigation.  It's a bit of gamble.  To have any effect it needs to be at
> least a quarter acre in size.  There is no way to prevent evaporation.  The
> deeper the lake the better your chances of having water all through the
> summer. The depth should not be less then 20 or 30 feet. 
> I don't have a lake.  I try to increase SOM (soil organic matter) so as to
> improve the water retention properties of the soil. A clay soil with high
> organic content has good soil structure and many pores that can multiply
> the amount of water held by the soil without being water logged. In the
> garden, I have been able to reduce irrigation by about 80% in the last 6
> years.  Weeds and grass are cut at the onset of the dry season so as to
> reduce transpiration.  The topsoil and mulch prevent evaporation through
> capillary action.  There isn't much one can do about deep percolation
> though.  Other strategies include, growing as much as possible during the
> wet season, and learning which crop will survive with little or not water,
> for examples: beans, tomatoes, squash, etc. 
> Dieter Brand, Portugal
>
>  
>
> --- On Wed, 8/27/08, Robert Waldrop <bwaldrop@cox.net> wrote:
>
> From: Robert Waldrop <bwaldrop@cox.net>
> Subject: Re: [permaculture] Conserving water in ponds
> To: "permaculture" <permaculture@lists.ibiblio.org>
> Date: Wednesday, August 27, 2008, 3:08 PM
>
> Other ideas about mitigation strategies would be
> helpful too.  RMW
>
> ----- Original Message -----
> From: "Robert Waldrop" <bwaldrop@cox.net>
> To: "permaculture"
> <permaculture@lists.ibiblio.org>
> Sent: Wednesday, August 27, 2008 9:07 AM
> Subject: [permaculture] Conserving water in ponds
>
> >A report has recently been released by the
> > Oklahoma Climatological Survey predicting that
> > as
> > a result of climate change, droughts in Oklahoma
> > will increase in frequency and severity.  As a
> > result, there is a discussion going on among the
> > producers-members of the Oklahoma Food Coop over
> > mitigation strategies.  One issue that has come
> > up
> > is "conserving water in ponds", presumably by
> > reducing evaporation.
> >
> > Any thoughts about that?  Would aquatic plants
> > that cover the surface of the water help?
> >
> > Bob Waldrop, OKC