So, I'm a newbie to permaculture- but have been gardening and raising livestock for 4 years now.
Very excited about permaculture, btw- and very excited about adding a pond to my landscape for a multitude of reasons.
My thought (pre-Permies, pre-permaculture) was sink a pond liner and make a pond.
But, Sepp says no pond liner. Paul in his podcasts has advocated no pond liner. The general consensus in the forum is no pond liner.
(I like it- the 'no pond liner' thing)
I am reading Sepp Holzer's Permaculture for the first time right now.
On page 98 Sepp advocates using a Pond Liner to seal the top of his Roundwood shelter from water intrusion.
So I have to beg the question: Why No Pond Liner in a Pond? Obviously Sepp is all about appropriate technology- which is great.
What is his reasoning for justifying the liner for one use and not the other? (Size? Functionality? Maybe appropriate technology is the root to his decision).
I haven't read Sepp's work, but in the case of the pond you should be able to seal it with materials on site, either with clay or by "gleying". Only in especially difficult circumstances would you resort to a membrane. Part of the problem with a membrane is that if it develops a puncture then the entire integrity of your dam is at risk. Plastic liners tend to be expensive.
Also, a dam that slowly leaks water into it's surrounding soil will act very much like a swale, topping up groundwater. This is usually a good thing, although perhaps annoying if your stored water is escaping. Water leaking into a building on the other hand is a big PROBLEM so you need to be especially sure that seal is water tight - hence plastic being appropriate.
Moderator, Treatment Free Beekeepers group on Facebook.
Andre Las : Another benefit to using a plastic membrane cover for structures like Sepp's and Paul W.'s Wafati and Earth Berm structures is to keep the moisture
content of the soils next to the structure dry -so that they have a measurable insulation value. Merely Wet or Frozen the '' R-value drops like a stone ! Big AL
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I would say that Sepp Holzer is not opposed to pond liners, its just that his ponds are very large and he has a cheap natural method to seal them.
There is simply no need for a liner in his situation. liners are quite expensive, especially large ones.
If he lived on sandy soil and had no pigs to do his gleying , then maybe he would use liners.
I have some small "ornamental" ponds near the house that store rainwater and they have rubber liners with old carpet as underliner.
But I also have a few " pond swales ", or " big random holes in the yard " that fill up during heavy rain and slowly leak out over the next days or week.
I throw lots of old leaves and organic materials down in these depressions or holes and they are slowly becoming naturalized environments.
I've just heard that cat litter is made of bentonite clay , which is what many people use to seal pond bottoms.
maybe I will experiment with some of that ...
It might be worth considering the very different nature of these applications. A pond liner in a pond is holding water that you are growing plants and fish in. The water is in contact with the liner for extended periods of time and your plants and animals are in that water for their life cycles. If anything leaches from the liner into the water, it can be taken up by your food supply.
Used as a roof material, water is in passing contact with the liner and runs off into the ground. Much less opportunity for anything to leach out, even if something does it is not then held where your food is growing.
It is a very different situation than you have where the liner is holding the water in place.
First of all, what makes you think a pond has to be sealed at all?
Ideally you only seal the dam resulting in your earthworks recharging the moiste upslope of the dam.
Such an unsealed pond is less likely to dry out than a sealed one, beacuse evaporated water can be replaced
by the water that is retained in the soil. Plus the water is available to the vegetation.
This is called the full water cycle. (As opposed to half-water cycle with isolated/sealed water features)
Secondly, there are situations where a liner is approriate. This video shows such a situation:
Please also look at the comment section under the video, there are a lot of people dogmatically saying "Pond liner bad. You bad. Use clay. This not permaculture".
However the author takes his time explaining in the comment section why the pond liner was the only option to
store water on the farm thus making the farm viable at all.
Lastly to answer why the liner in the roof is more ok, than in the pond:
a) The pond liner in the pond is always wet, therefore exposed to chemical whaetering which makes it last shorter
thena the liner in the roof.
b) The pond line in the pond is more prone to mehanical damage, especially when not protected properly
c) When the pond liner fails some decades down the road, it is possible that the future owner doesn't care about properly disposing/replacing
of the liner which is bad. A properly build clay pond can prevail for hundreds of years. Whereas the pond liner in the roof
is more likely to be removed once the structure reaches its end of life.
Please note that you can also use clay to seal the roof of your structures, there were structures in northern europe that were dry for over a thousand years
until the vikings decided to plunder the insides...entering through the roof and thereby destroying the structure.
"Sealed" has to be understood in context. A pond that does not hold water reliably isn't a pond, it's a hollow, or a hole in the ground or a pit. So if your pond has water in it year round and it isn't being continually refilled by a fast flowing spring to make up for what is being lost 8nto the soil, then the pond is "sealed" functionally.
On my site we have vernal ponds that appear in low areas when our water table breaks the surface of the ground. But if I make a hole for a small pond, it will only have water in it when the water table is above the bottom of the hole. Our sand will not hold water. To have a non-seasonal pond here, we have to take action to seal the sand. The dam on a pond isn't watertight either, if you want to be technical about it. It restricts the flow very severely, but water will move through an earthen dam. Just really slowly. ;)
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