[permaculture] Suitablility of clay for building ponds

christopher nesbitt christopher.nesbitt at mmrfbz.org
Tue May 5 07:57:23 EDT 2009


The term for biological barriers is "gley"ing the pod.

http://resources.alibaba.com/topic/41782/How_to_create_a_pond_with_gley.htm
On May 5, 2009, at 4:57 AM, Dieter Brand wrote:

> My soil is about 2 to 3 feet of yellow clay mixed with stones on top  
> of a thin layer of grey clay which is formed on top of the rock  
> bed.  Sorry, don't know the technical names for these types of clay.
>
> Anyway, the yellow clay will dry out slowly during the dry season  
> through capillary action, surface evaporation and plant  
> transpiration.  However, some of the humidity in the yellow clay  
> layer will slowly percolate down the hillsides through water lines  
> on top of the grey clay which is 100 % water-impermeable and which  
> therefore doesn’t let through any water.
>
> I made a number of water catchments by excavating the soil down to  
> the grey clay and by using some of the grey clay to form a barrier  
> downstream.  This forms a catchment hole fed by waterlines from  
> upstream that doesn’t let through a single drop of water  
> downstream.  I lined the catchment holes with large stones to  
> prevent the grey clay from washing out and to prevent the water from  
> getting cloudy.  The position of the intake tube assures that the  
> water in the catchment hole is always at a certain level so that  
> there is no risk of cracking in the clay when it gets dry.  Except  
> for the tubing, I only use materials found on-site.
>
> Upstream of the water catchment, I made a large hole which I filled  
> with coarse sand, pebbles, small and large stones to filter the  
> water before it goes into the catchment.  We have a lot of white  
> quartz stones on our land which are ideal for that purpose.  I  
> planted different types of plants into this natural filter so that  
> the roots spreading between the sand, pebbles and stones may take up  
> impurities in the water.  I cover the catchment holes to prevent  
> evaporation during the summer.
>
> The algae, frogs etc. in the water catchments provide a biological  
> environment that is beneficial for the garden soil which I irrigate  
> with that water.  With a daily flow-through of a few thousand liters  
> in winter and a few hundred liters in summer, I'm not unduly worried  
> about nasty things that may develop in stagnant water.
>
> What do you mean by a “two acre foot pond”?  Is that a pond of two  
> acres surface area with a depth of one foot?  That wouldn’t be of  
> much use in my opinion.  It would be like a paddy field which you  
> can do when you have more than enough water anyways.
>
> Dieter Brand
> Portugal
>
> PS:  In France and some of the other Celtic regions they used a  
> technique for making a pond impermeable by a microbial layer made  
> from organic materials.  I can’t remember the name (that’s what old  
> age does to you ;-)) nor how exactly this organic layer is formed  
> (perhaps by compressing manure and straw???).  I never used it  
> because it can only work if the pond is permanently filled with  
> water.  In severe arid conditions, as here in the Saouth of  
> Portugal, the water level in ponds or artificial laces can fall by  
> several inches per day for 6 or more months of dry season with high  
> temps.  If I can remember what the technique is called I will let  
> you know.  But perhaps someone else can chip in here.
>
>
>
> --- On Mon, 5/4/09, Gene Monaco <efmonaco at comcast.net> wrote:
>
> From: Gene Monaco <efmonaco at comcast.net>
> Subject: [permaculture] Suitablility of clay for building ponds
> To: permaculture at lists.ibiblio.org
> Date: Monday, May 4, 2009, 12:06 AM
>
> I have a little background in this, and I am also trying to fix a  
> leaking
> pond made by a predecessor.
> The type of clay and how it is compacted is what it is all about.
> Ideally, you can find clay that is a deposit from eroded volcanic  
> ash.  This
> is very very fine and highly expansive.  Around here it is known as
> montmorillonite.  Bentonite is a type of montmorillonite, and is  
> commonly
> used in construction.
> Modern methods sandwich about 5 or 6 mm (1/4") of bentonite between  
> two
> sheets of something.  Earlier products used paper (like drywall) as  
> the
> binder, but now they use geofabrics as well for the pond liners,  
> especially
> for landfills.  They also sell bentonite pellets in 50 lb bags that  
> you can
> till into the insitu soil if it is already clayey and dry enough to  
> till.
> The liners are very effective but are expensive.  They are however  
> efficient
> as far as the clay is concerned because the manufacturing process puts
> precisely that 1/4" between the sandwich sheets.  If you try to till  
> it in
> by hand or spread it out, you could never get 1/4" uniformly spread  
> out
> over
> the surface; rather, you have to put about a 2" layer down and then  
> till
> it
> in as best you can, or cover it with 18" of packed cover.
> The key is that the expansive clay has to be contained by pressure  
> over it.
> This means in practicality, that you have to over excavate the pond  
> 18" or
> so, lay down the sheet (or till in the 2" layer) and then cover it  
> with
> 18"
> of overburden, preferably clay.  That way when it gets wet and  
> expands, it
> will have nowhere to go and will form the seal you're trying to  
> achieve.
> If you till it in to the top 6" without the overburden, you are taking
> your
> chances that when it expands it will lock into the surrounding  
> particles
> instead of fluffing and allowing the water to run around it,  
> rendering it
> useless.
> The principles described here are applicable to any clay site.  You  
> need
> something impervious enough and packed down enough under enough  
> pressure so
> that when it expands, it won't fluff so much as to allow the water  
> to run
> around (through) it.  So the type of clay and how it is installed is
> everything.
>
> One detail is at the top.  I've seen a number of ponds that held  
> water to
> the design level at the beginning, but then dropped a foot or two or  
> more
> after a few years.  This is because the clay at the edge is not  
> under the
> weight of the water and tends to fluff.  Also, animals climb in and  
> out
> right at the top edge and tear it up as well (especially true for EPDM
> liners).  To deal with this, you need to run the clay seam back far  
> enough
> outside the edge of the pond and pile up an 18" or 2' berm around the
> edge,
> plus add rocks for weight and protection from animals.
>
>
> Gene
>
>
> Date: Sat, 2 May 2009 12:47:26 -0700 (PDT)
> From: Rain Tenaqiya <raincascadia at yahoo.com>
> Subject: [permaculture] suitablility of clay for building ponds
> To: permaculture at lists.ibiblio.org
> Message-ID: <655408.34901.qm at web38107.mail.mud.yahoo.com>
> Content-Type: text/plain; charset=iso-8859-1
>
> I'm building a two acre foot pond to irrigate our permaculture
> demonstration
> site and I'm having difficulty identifying appropriate soil for  
> building
> the
> dam and lining the pond.? We have quite a mix of soils varying from
> sandstone-derived loam to serpentine-derived clay.? Is the clay  
> content the
> most important variable?? We have some very high clay content soil  
> that has
> a crystal like structure when exposed.? It is very expansive, and  
> when dry,
> it gets blocky and is easily broken up.? I think it would be fine  
> where it
> will be under other layers or always wet.? Does anyone have any  
> answers or
> comments on this?
> ?
> Thanks,
> ?
> Rain
>
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_____________________________
Christopher Nesbitt

Maya Mountain Research Farm
San Pedro Columbia, Toledo
PO 153 Punta Gorda Town, Toledo
BELIZE,
Central America

www.mmrfbz.org





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