[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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