permaculture

[Scott Pittman <pci@permaculture-inst.org>]

At 09:37 AM 11/13/02 -0500, you wrote:
> At 10:23 AM 11/12/02 -0500, you wrote:
> >   When googling "water harvesting" I found an African site which had lots of
> > water catchment berms used for growing trees. I thought I'd adapt that
> > concept in an easier way and create a diamond pattern on my sloping crop
> > fields using the half V trencher instead of so many berms, like a cocked
> > tic-tac-toe board or a giant piece of graph paper on a slight rotation off
> > alignment with the slope. Thus we could plant all shade and orchard trees in
> > the intersections and all extra unabsorbed water in that 'quadrant' would be
> > channelled by the surrouding half V trenches directly to the trees, thus
> > multiplying the use of rain- as if several times the rainfall had occurred.

In PC we call this type of arrangement "net and pan" or boomarangs, or fish 
scale, all of these configurations work well on steep slopes as long as you 
have sufficient catchment at the end of the water run.  It is a fairly 
simple matter to calculate how much rain you receive on a given area and 
then calculate how much water you want to deliver to the target tree in 
each segment.  You also have to build up the sides of the grid with what 
ever material is available on the slope ( dirt, rocks, dead branches, etc), 
to direct the runoff to your catchment pan where you have planted the 
tree.  I have only seen the sides of these grid systems built up and never 
trenched.  Probable because they have only been used on slopes where it is 
too steep to run equipment.  If you can run equipment then it is probable 
better to build swales where you are distributing the water all across the 
slope equally.  If you want to concentrate the water in a swale then put in 
strawbale wicks in those areas, or dig the swale a little deeper in the 
area where you want to focus the water.

Scott P.



U