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circular swales.

 
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i have been musing about the possible benefits and uses of circular swales on areas with virtually no slope to them. in my head i imagine a circle about 50 feet wide, the berm planted with mesquite tree. the center of the swale circle would be dug out to create a low point, here you could maybe plant a tree that does well sheltered from the wind and grows a little taller. i havent really thought of the species i would plant on this idea. anyway, the berm has a mesquite thicket and we'll say the middle is a pomegranate tree made to grow tall, and all around the pomegranate is grazing for sheep or goats or what have you.

anyway, i was just wondering how real life this idea was. i like the idea of digging large circular swales on flat terrain because it satisfies a subtle need i feel for things to be circular. i just like circular things i guess. but regaurdless, i feel as though it would trap more water into less area, has applications for growing food for animal and human consumption, increases soil fertility, a source of timber, a structual pen for animals.

has anyone seen anything like this? i was looking at a picture in a forum about airwells

http://upload.wikimedia.org/wikipedia/commons/thumb/0/02/Lanzarote_La_Geria_Weinanbau.jpg/250px-Lanzarote_La_Geria_Weinanbau.jpg


anyway, that was the inspiration, i saw that and said, hey, those rocks should be a swale and that whole thing should be a lot bigger.

so yea.
thanks
 
gardener
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Location: Grand Valley of Colorado's Western Slope
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Joel,

That's a beautiful photo, I can see why it caught your eye.

I can't tell where you live, and your climate does have some bearing on swale design. The drawback to a circular swale is that it has a smaller surface area than the same volume in a rectangle or crescent. You said it looked compact, would trap more water in less space.... and it will, and providing less surface area for the water to soak in, it will hold the water above ground longer. This could be desirable or not, depending on if you want the water above ground. For me, in my circumstances, I would lose more to evaporation before it was under ground. Being in an arid climate, that would not be what I wanted. On the other hand, it would collect the rain to a central point, using the water from the whole surface area of the circle to water the one central pomegranate.

If you planted planted a pomegranate tree in the middle, and at the lowest point, in a clay soil with lots of rainfall, when would it ever have aerated soil at it's roots?

This questino kind of reminds me of something I did at my place. I built a runoff diversion contour to keep the water out of the greenhouse, which I made the mistake of building at the lowest corner of my property. Think of a half circle retaining wall, with a berm build up inside the curve, and the rest of the circle defined by digging the soil up and out of the hole... a place for the rare runoff situation. On the berm behind the retaining wall, I planted hops. Then I wondered how I would water them. I would have to fill up the whole round hole before the water reached the level of the hops roots. Well, I brought the irrigation furrow around the curve up at the level of the hops plants. That way, I could get the water to them "right now", and the water would be soaking in the whole time the hole was filling. Then I kept the furrow carrying the water high, running it round and round as it went to the bottom of the swale or pond. It is a spiral ditch, and it is quite hypnotic to wathc the water going round and round. I did not really plan it that way, did not really set out to make a spiral ditch, but I love it. Probably in the next season, I will need to elongate it into an oval, but I hope I still can keep that spiral flow.

There is no reason not to make a "round swale" if it appeals to your sense of esthetics, and you have the space. It will not be as efficient at delivering water underground in a large area, it will concentrate water to a small area... Just make sure you consider all the variables of your particular site, clay or sandy soil, how much water comes down how often. And make sure you attune your plants to the conditions you create with your round swale.

Have fun with it.

Thekla
 
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Hi Joel:

What you're referring to actually has a name (probably several names) but I know them best as "infiltration basins" and they are indeed wonderful for properties with very little slope. We use them here in the Sonoran desert all the time.

If you haven't already, check out Brad Lancaster's two volumes on "Rainwater Harvesting for Drylands and Beyond" Volume 1 is about water harvesting in general and Volume 2 is specifically about earthworks including all kinds of variations on swales for different land profiles (flat, sloped, steep). There are also some really great pictures in this book showing HOW to plant these basins for maximum yield - essentially plant higher water use plants in the swale and natives going up the sides or at the top. He has a whole "mesquite guild" outlined in the book and shows how to plant this.

And I agree with Thekla, you'd want to keep a pomegranate out of the low point of a swale/ infiltration basin - too wet, even here in the HOT dry desert. Here in Phoenix, I would plant a pom on the slope so it's a little above the bottom. Especially if you have clay soils which have a slower percolation rate and little aeration.

Where are you located? You sound like you are in the SW if you are interested in mesquite and poms?

 
steward
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Here is what Sepp does.

 
Thekla McDaniels
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I'm inspired. I liked having the new fact that it increases surface by 1/3. I had earthwork on my schedule for next season, and with this short clip, I'll have an even better idea what to do, AND what to tell people who ask what I am doing.

But I did not see the wood going into those berms. Maybe I blinked!

Thanks for posting

Thekla
 
Posts: 1975
Location: Zone 5 Wyoming
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I understand your thinking and agree with Jennifer that they are infiltration basins. I'm doing many of them myself. Probably not as deep as the ones in that picture though since I'll be doing them with a tractor bucket. I will be planting all of my trees in the middle but modifying it a little in that I am going to do a planting "mound" in the very center. So it will get water but will be a little bit out of it. I haven't refined the idea yet. Depending on how big I do the basins I might do a few planting mounds and have a few trees per basin. Of course, I need to put real thought into this as I'm doing a U-pick. I don't need to have deep holes for people to get in and never get out of. I imagine I'll have to do mine somewhat shallow.
 
Thekla McDaniels
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Hi Daniella,

One thing that might work for your deep swale/ infiltration /catchment and U-Pick situation is if you fill the catchment basin with something like coarse wood chips. LOTS of "airspace" that can give way to water when the water comes, it decreases evaporation, and retain water them selves, and will decompose creating humus. And maybe release heat and / or grow mushrooms.

What do you think? Is there a place for that idea in your plan?

Thekla

 
gardener
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I did a back-search for the image through Google and in the agriculture section of the Lanzarote wikipedia article it discusses how the image works.


The German wikipedia page for Lanzarote says that the above image is a type of dryland farming typical to that region. The rocks absorb heat during the day and release it during the night. Likewise, the rocks stay cold during the morning when it is hot, and as a result, water in the air condenses on the rocks and drips into the soil.

On the English version of the wikipedia page for Lanzarote, it states that the rocks also protect the plants from harsh winds, acts as an infiltration basin, and harvests morning dew.

And on permies, we have already had a pretty thorough discussion on air wells which function on the same principles as the above image.
Here are some of the highlights from the discussion:

What an air well looks like:


The Talus Garland Effect


The Groasis Box


I went back to the wikipedia page on Lanzarote, and the Spanish version had a lot on the culture of Lanzarote and less about the agriculture. On further inspection, I checked a few more of the world's major languages and found the French wikipedia page on Lanzarote gave about the same information as the German wikipedia page except with a few details about agricultural history added.
 
elle sagenev
Posts: 1975
Location: Zone 5 Wyoming
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Thekla McDaniels wrote:Hi Daniella,

One thing that might work for your deep swale/ infiltration /catchment and U-Pick situation is if you fill the catchment basin with something like coarse wood chips. LOTS of "airspace" that can give way to water when the water comes, it decreases evaporation, and retain water them selves, and will decompose creating humus. And maybe release heat and / or grow mushrooms.

What do you think? Is there a place for that idea in your plan?

Thekla



I could see wood chips working well for me. They are fairly inexpensive as well, so that's always good.
 
Posts: 97
Location: St. Louis, MO
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Thekla McDaniels wrote:

This questino kind of reminds me of something I did at my place. I built a runoff diversion contour to keep the water out of the greenhouse, which I made the mistake of building at the lowest corner of my property. Think of a half circle retaining wall, with a berm build up inside the curve, and the rest of the circle defined by digging the soil up and out of the hole... a place for the rare runoff situation. On the berm behind the retaining wall, I planted hops. Then I wondered how I would water them. I would have to fill up the whole round hole before the water reached the level of the hops roots. Well, I brought the irrigation furrow around the curve up at the level of the hops plants. That way, I could get the water to them "right now", and the water would be soaking in the whole time the hole was filling. Then I kept the furrow carrying the water high, running it round and round as it went to the bottom of the swale or pond. It is a spiral ditch, and it is quite hypnotic to wathc the water going round and round. I did not really plan it that way, did not really set out to make a spiral ditch, but I love it. Probably in the next season, I will need to elongate it into an oval, but I hope I still can keep that spiral flow.

Thekla



This sounds interesting... do you have any photos?
 
Thekla McDaniels
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Hi Tom,

It's been a few years since I built it.

The hops cover the trellis, and early succession plants cover the bare dirt, but here it is as originally built. It has never leaked or overflowed or washed out.
spiral-needed.JPG
[Thumbnail for spiral-needed.JPG]
spiral-2.JPG
[Thumbnail for spiral-2.JPG]
backside.JPG
[Thumbnail for backside.JPG]
 
Thekla McDaniels
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and here are a couple more
IMG_spiral-full4470.JPG
[Thumbnail for IMG_spiral-full4470.JPG]
older-spiral.JPG
[Thumbnail for older-spiral.JPG]
 
Tom Harner
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Location: St. Louis, MO
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I love it! This idea is being stored away for later. Thanks for sharing!
 
Thekla McDaniels
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Thanks Tom, Sorry it took me so long to post them, they're all old, but it's spring. It seems that what I do in spring will be multiplied by the growth cycle. Things that I don't get done will likely have to wait for the next spring. With a belief like that I am driven! But it is glorious work. Last year the beautiful ditch got covered in weeds, and one of the things I hope to do this year is uncover it, and it's wider meander on the uphill side. Once it is uncovered, I could set in motion the plant community I want to grow there. That bank below the hops is south facing, and I'm thinking I could try some pomegranates there. Perhaps your interest will inspire and motivate me. And I'll even get photos...

This thing is quite functional, as I explained and I think the photos make evident. Without it, I could not water the lowest corner without overflowing my neighbors' property. A happy accident for me, and I'll be delighted if others benefit from it.

If you get out this way, I hope you'll come have a look!

Thekla
 
Tom Harner
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Well, if it helps... I want to see photos of the updates you make in the next few weeks/months.

Oh, any place a small soakage pond is practical the use of the spiral ditch would make a wonderful addition for surface irrigation and aesthetics. In other words, the question of practicality is more than satisfied. My one practical question is where does it overflow when filled? back "up" the level swale?

I'd love to take a tour, but I don't travel all that much.
 
pollinator
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Theckla, I really like your spiral! One of those 'obvious in hindsight' things; raised herb spirals are everywhere, especially where they don't work too well... but I've never seen an inverted spiral before. I'm also interested to see how things progress with it.

Regarding the original post, the designer's manual references infiltration basins and similar systems for desert/dryland situations. You wouldn't put them somewhere you expect them to receive flow, either. The idea is you can use them where there should never be plausible risk of overflow.

However, if you are in a climate with more water, you'd definitely need to amend the design to suit; if you have greater rainfall and need to expect overflow, you'd probably make this into a net and pan system, with a bunch of circles interconnected to allow for overflow from each one, and some exit or storage point at the bottom of the system. At the very least you'd need a level sill at the low point to minimize erosion, but this seems a rather odd way to do things.
 
Thekla McDaniels
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Ah, Dillon,
You're looking out for me! And for anyone who might like it and want to try it. You are providing the rest of the story, and connecting my project to the design manual!

I am in the desert. With porous soil composed of very fine sand and a little clay and no organics. It only fills when I run the irrigation water. I discovered that when using furrow irrigation, one must run the water long after it reaches the end of the ditch. This is how I can manage it at the lowest corner. I guess it is an infiltration basin, but most likely I'll continue to call it a swale.

I did make a safety thing though, because if it overflows it will take itself out. Moving water flowing over the top of a little berm is not a good thing. Not just flooding my neighbors, but carrying them a lot of my soil. They would not be happy. I want good relations with them. Near the top, I made a drain pipe that goes through the berm and pours into a hole about 4 feet deep and about that same diameter. If I leave the water on long enough, the water level reaches the safety drain and pours into the hole. It would take many hours to fill the hole and when it overfilled, the water would run across the surface of the ground, soaking in. I have one more safety feature, a dry ditch that follows the contour, crosses the path of flowing water, were there ever to be flowing water on the surface.

I have heard the term "net and pan" and wondered what it was. Your use of the term here makes it clear, and there is a little of that here at my place also, though it is sloping ground, and water between the holes would not move in all directions.

Anyway, I am glad you like it.
 
We've gotta get close enough to that helmet to pull the choke on it's engine and flood his mind! Or, we could just read this tiny ad:
Heat your home with the twigs that naturally fall of the trees in your yard
http://woodheat.net
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