[permaculture] Rainwater harvesting pond story

Suraj Kumar suraj at sunson.in
Tue Aug 11 22:18:45 EDT 2009


Hi John,

Thanks for all the excellent points. I did read about the ideal slope
but I was ultimately limited by "space". I was expecting that
eventually the pond will settle into a, like you said, "Happy" place.
I'm guessing the process will be slow (say, over 5 years?). In the
meanwhile we plan to plant http://vetiver.org/ on the 'edges' of the
steps in the pond. Vetiver is indeed a magical grass - it can grow in
the water or in the desert - its roots can grow upto 7 ft long in just
2 years. So if the steps hold good for just about 2-3 years, the
vetiver will start compensating for the losing structural stability.
The banks of the pond are reasonably structurally stable too (a 1:3
ratio is maintained) and are 4 ft above ground level. There are pipes
leading water into the pond and I hope the banks will hold quite well
for atleast a few more years until the vetiver starts reinforcing the
soil.

Regarding cattle in the pond: The locals said "Water will definitely
stay throughout the year. What you're doing is a good thing" and I
hope they're right. We decided that we'd take any further action only
if our pond runs dry after the rains. That is probably because I'm
hugely inspired by Mr.Fukuoka and I say he is totally right about
saying "We don't know anything". Nature is hugely complex and it is
self-stabilizing in many ways. Nature has its own pace and when
someone says "being in harmony with nature", I believe, thats what it
is - to work at Nature's pace. It might take time but maybe that's the
way to improve my own self too - by not expecting "too much" from
nature, by working on the ultimate cause of most of this disharmony in
knowing "Need" vs "Greed".

On the lighter side, I plan to grow vetiver on a 7 ft tall mound of
soil. After about 4 years, we could "dig out" an underground shelter!
Since the vetiver will hold the soil intact like the steel wires do to
RCC, we should just be able to happily dig horizontally without
worries about stability. The digging might need some heavy machinery
but it should be doable, isn't it? If I can wash the soil away, I'll
get a cool looking semi-transparent shade ideal for dozing off after a
good lunch!

  -Suraj



On Tue, Aug 11, 2009 at 10:43 PM, John Thomas
Naisbitt<johntnaisbitt at gmail.com> wrote:
> Agreeing with Brent, the slopes should be at a 1:4 gradient. A slope of
> natural impose usually rests at around 1:1.5 (eath fill natural fall,
> natural sluff) which is only the beginning of the initial sluff which will
> occur within the first few months without a retaining wall. (Which brings up
> a safey monster of its' own.) After that, the pond wall will most likely
> begin to create its' own slope "Healing" process by creating its own stable
> slope gradient depending on the soil compostion.
>
> If your operator had been on top of it, he could have suggested that you
> create the 1:4 slopes as it would minimize the effort of digging towards the
> toe of the machine which increases the time it takes to dig the excavation
> and work at a slope away from the machine, which keeps the boom of the
> excavator at a comfortable distance and near the optimal swing radius for
> moving material from the excavation. This is dual purpose (stacking
> functions) as it allows the operator to keep his machine on the 1:4 slope
> and further the depth of the excavation  to reach the desired elevations,
> thus opening the possibilities of reaching your goal for the desired volume
> of the pond. The only real restriction to this is the space available for
> the pond as this does reduce volume possibilites.....in which case, you
> could steepen the slopes to 1:3 which is still safe for excavator operation
> *as long as the operator is trained in woking on a slope.*
>
> The only other thought I have is that, being made of natural soils, no
> matter what slope you excavate, the pond slopes will continue to settle
> until the soils find their "Happy" place. Have you considered running cows
> in the pond to build up bacteria (for the pond slime), work the slopes and
> pond bottom, and compact the soils? (A kind of cow "romper room to eat and
> play"; or cow "mosh pit", if you will.....no stage diving please.)
> **
> I do not intend to be misleading as to the intentions, skills, or mindset of
> your operator, the hole is there.....make the best of it and please be safe
> around the edges.
>
> John
>
> *
>
> * On Tue, Aug 11, 2009 at 9:38 AM, Brent McMillan <brent at gp.org> wrote:
>
>> As someone who use to work in the engineering department of a Sanitary
>> District, the slope should not exceed 1:4 (One foot of rise to four feet
>> of run)
>>
>> Anything greater than that is unstable and will probably only collapse
>> over time anyway until it gets to a slope close to that.
>>
>> Sincerely:
>>
>> Brent McMillan, Steward of Woodhaven
>> Avilla, IN, USA
>>
>> Suraj Kumar wrote:
>> > Hi Guys,
>> >
>> > Your questions are all valid and my ideal shaped pond would have
>> > looked exactly like a bowl. Minimal surface area, maximum volume. A
>> > smoothly sloping pond would be, to mathematically put it, made up of
>> > an infinite number of steps. In my case, its just 3 steps.
>> >
>> > Each step decreases surface area of water exposed to sunlight.
>> >
>> > However, the JCB operator mentioned in advance that the cost of the
>> > operation will be proportionally expensive and time consuming - hence
>> > we had to settle with 3 steps.
>> >
>> >
>> > Cheers,
>> >
>> >   -Suraj
>> >
>> > On Tue, Aug 11, 2009 at 8:29 AM, Lisa Rollens<rollens at fidnet.com> wrote:
>> >
>> >> Very interesting, Suraj, and quite a well done write-up.  I also do not
>> see
>> >> how the straight sides will stay that way.  Surely they will wash into
>> >> gentle slopes.  Another consideration...what if someone falls in.  Can
>> they
>> >> he/she get out or would drowning possibility be high...esp a small
>> child?
>> >> That would worry me.  Even a dog would have a hard time climbing out
>> without
>> >> a slope.
>> >>
>> >> Just my first impressions, hope they're useful, Lisa
>> >>
>> >>
>> >> ----- Original Message -----
>> >> From: "Suraj Kumar" <suraj at sunson.in>
>> >> To: "permaculture" <permaculture at lists.ibiblio.org>
>> >> Sent: Monday, August 10, 2009 10:28 AM
>> >> Subject: [permaculture] Rainwater harvesting pond story
>> >>
>> >>
>> >>
>> >>> Hi Guys,
>> >>>
>> >>> On our tiny acreage farm (1.86 acres), we recently finished building a
>> >>> 3 stepped 3825 sq.ft. sized pond with a max depth of 22 ft. We had
>> >>> three goals:
>> >>>
>> >>>   1. Store water for irrigation needs during the dry-seasons (post
>> >>> monsoon and then pre-monsoon)
>> >>>   2. Conserve the constructed pits / wells / dams / hedges / whatever
>> >>> structure
>> >>>   3. Storing run-away water / Retrieving stored water must be doable
>> >>> using as little energy as possible
>> >>>
>> >>> We rented out a backhoe excavator (JCB-3CX) and two tipper tractors
>> >>> for this job.
>> >>>
>> >>> http://wiki.sunson.in/rain_water_harvesting explains the design in
>> >>> terms of satisfying these above three goals.
>> >>>
>> >>> Please feel free to let out your comments!
>> >>>
>> >>> Cheers,
>> >>>
>> >>>  -Suraj
>> >>>
>> >>> --
>> >>> "The Greatest Shortcoming of the Human Race is
>> >>> our Inability to Understand the Exponential Function"
>> >>> Dr. Albert Bartlett
>> >>> _______________________________________________
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-- 
"The Greatest Shortcoming of the Human Race is
our Inability to Understand the Exponential Function"
Dr. Albert Bartlett



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