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Using a Trencher/Ditch Witch to dig swales?

 
Posts: 18
Location: Pomona, CA
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Hey all,

I've got a fairly large area that I'd like to cover with swales and was wondering if anyone has used a small two-wheel, walk behind ditch witch or a ground hog trencher to dig them. I don't feel like paying a crew to help me dig and the rental rate on the trenchers from home depot are fairly reasonable. The only drawback I foresee is that these trenchers tend to dig fairly narrow trenches. I was thinking of just digging the trenches down to 24" or so then going back with a shovel to widen them by breaking one of the sides and bringing the depth back down to 14-18". Could this work? Anyone have experience doing this?

Anyways, my acre is pretty flat. I was going to make a series of two trenches approximately five feet from each other, with all the back fill going in between. After the swales are done, I will fill them with wood chips, put drip over the woodchips then plant trees in the shared berm.
 
Posts: 2679
Location: Phoenix, AZ (9b)
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Tony de Veyra wrote:I've got a fairly large area that I'd like to cover with swales and was wondering if anyone has used a small two-wheel, walk behind ditch witch or a ground hog trencher to dig them. I don't feel like paying a crew to help me dig and the rental rate on the trenchers from home depot are fairly reasonable. The only drawback I foresee is that these trenchers tend to dig fairly narrow trenches. I was thinking of just digging the trenches down to 24" or so then going back with a shovel to widen them by breaking one of the sides and bringing the depth back down to 14-18". Could this work? Anyone have experience doing this?

Anyways, my acre is pretty flat. I was going to make a series of two trenches approximately five feet from each other, with all the back fill going in between. After the swales are done, I will fill them with wood chips, put drip over the woodchips then plant trees in the shared berm.



Hi Tony:

Usually swales are used to capture water that enters your property, slowing and spreading it so that it rehydrates your landscape. Native trees are planted on the uphill sides of these and a mix of food producing trees and legumes are planted on the downhill side where the soil excavated from the swales is piled into a berm of soft soil.

Swales are dug on contour - land of similar elevation - each swale following a contour line. They are rarely exactly parallel to each other. So say, across your acre of land, you go from an elevation of 1000 ft to an elevation of 1030 ft. (a fairly flatish property) If this were my property, and I wanted to put in two swales, I'd probably choose to put the first one at 1020 ft - so I would map out a line across my property that is at 1020 ft elevation and dig my swale along that line, piling the earth dug from the swale on the downhill side. I'd probably dig my next swale at 1010 ft elevation, so I'd mark another line to determine a line across my property that was at that elevation and dig my next swale there. Note that in some places, these two swales might be very close to each other and in others, very far away. Again the earth from the swale would go on the downhill side.

While you can put some mulch in the swales, irrigation is not necessary. UNLESS you are growing things inside the swale - which is a dryland technique. In your scenario above, irrigation would be used on the berm where the plants are growing. This growing area should be mulched and the irrigation put UNDER the mulch (especially if you are in an area with high evaporation).

Can you tell us more about what your overall goal is for this system and what your climate is like (amount of rainfall, soils, elevation across your property, temperature range, etc). Those things will help determine if swales are a good option or if some other type of water harvesting catchment might be better like infiltration basins. If you have pictures of your property you can post, that would be helpful too.

Swales on contour on Jack Spirko's land (flat-ish)

 
Tony de Veyra
Posts: 18
Location: Pomona, CA
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Hey Jennifer,

I suppose I used the wrong term, didn't I? Can't have much of a swale if you don't have an elevation shift (which I really don't). I suppose infiltration ditch would be a better way to describe what I am trying to dig with the trencher.

Here's a keyboard picture of what I want to do:

===16" deep trench, 12" wide===
---drip irrigation-------------
--------trees------------------
--------5 ft wide berm---------
-----------drip irrigation-----
====Mulched over trench========

I'm in the high desert region of CA, Mojave Desert. 1000 chilling hours, average annual low 15F, Annual rainfall at 10" or so, all in the winter.

My long-term plan is to cover the whole place with trees. I want to try and stack an orchard on top of a pasture. I want to collect rare fruit and have a collection of all the best temperate and desert fruits from around the world.
2014-01-27-08-09-11.png
[Thumbnail for 2014-01-27-08-09-11.png]
 
Jennifer Wadsworth
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Location: Phoenix, AZ (9b)
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Thanks for the info!

Sounds like you want to create a dryland food forest - I'm with you there!

What you'll probably find on your land is that your house sits at the highest elevation on the property. The top of your watershed is the roof of your house. You'd probably be interested in a system similar to mine whereby you reclaim as much water as possible - both rainwater and greywater - and use it in your system.

Although my property is only 1/6th acre, I have a number of infiltration basins around the house that capture my greywater from my shower, laundry and sinks, and even a "dark grey water" system for the kitchen sink. Rainwater is also collected in these basins from the roof of my house. The basins are structured so that any overflow goes to a slightly lower (like 6-8") basin. The lowest area in my yard, by design, is the middle. I plant trees and shrubs IN these basins (on small raised areas) and then mulch them heavily. Because there is less greywater and rainwater farther away from the top of my watershed (the house) I plant the thirstiest trees close to the house and the hearty natives (for me, mesquites, palo verde/palo brea, acacias, etc) further away. You can follow the installation of one of these basins in a post I wrote for Permaculture Global here: http://permaculturenews.org/2014/01/14/laundry-to-landscape-urban-greywater-installation-greening-the-sonoran-desert-phoenix-arizona/



If you haven't already read Brad Lancaster's excellent books on rainwater harvesting - they are worth a read. Volume 2 is all about earthworks for various situations. Brad also teaches for Watershed Management Group in Tucson. They hold a very rigorous Water Harvesting Certification program if you are interested in attending. This year they are offering it in both Tucson and Albuquerque. Past host sites included Phoenix and Santa Barbara.
 
Posts: 231
Location: Southern Minnesota, USA, zone 4/5
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The ditch witch idea sounds like it would probably work great for my climate and soils, I think I'll try it!

You should make sure that the water you're capturing doesn't go too deep too quickly (making it less useful to you but still infinitely better than just running away!) especially if your land is flatish and there's not chance to tap into it farther down hill. But if your doing deep rooted trees this might not be a big problem anyway.

This probably requires a good understanding of your soil properties. Please let us know how this works out for you!
 
pollinator
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Location: Kent, UK - Zone 8
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From that photo it looks like there are roads around your property, Can you look at harvesting some of the surface runoff from these, perhaps divert a culvert onto your land to fill an infiltration basin or swale? If the water would otherwise be going to a storm drain it looks like there is scope for easy improvements.
 
Tony de Veyra
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Location: Pomona, CA
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@Jennifer: I'll definitely have to look into Brad Lancaster's books. I really want to do greywater, too, installing the bypasses into my plumbing seems like it will be difficult. I've already figured out what to do with my urine (fertilizer for duckweed pond) and feces (black solder fly maggots) so recycling the shower and sinks is the last thing.

@S Haze: great point about the sandy soil and water infiltration rates, I could probably make the infiltration trenches shallower. I will definitely let you know when I get started. As I said, I'm still in the planning phases, won't be able to get to any real significant work until after graduation in june.

@Michael: Yeah, I've thought about harvesting from the roads. We don't actually have any storm drains or gutters on the roads--rain water tends to just pool off to the side for a few days before infiltrating/evaporating over the course of a week or so after a decent rain. I will eventually have to dig in around the sides of the road and install a french drain or something that leads into my property before backfilling the road shoulders with river rocks or pea gravel.
 
Jennifer Wadsworth
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Location: Phoenix, AZ (9b)
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Tony de Veyra wrote:@Jennifer: I'll definitely have to look into Brad Lancaster's books. I really want to do greywater, too, installing the bypasses into my plumbing seems like it will be difficult. I've already figured out what to do with my urine (fertilizer for duckweed pond) and feces (black solder fly maggots) so recycling the shower and sinks is the last thing.



Also check out Art Ludwig's books on greywater. Greywater is actually a better (and far more reliable) source of water than rainwater for us in Phoenix. If you're going to use water, might as well get as many uses out of it as possible!

As for being hard to access, my bathroom tub/shower was hard to access, so I just built one outside. It's part of a multi-use shade house along the east side of my house that also contains my chicken yard, compost bins and propagation area.




Tony de Veyra wrote:@Michael: Yeah, I've thought about harvesting from the roads. We don't actually have any storm drains or gutters on the roads--rain water tends to just pool off to the side for a few days before infiltrating/evaporating over the course of a week or so after a decent rain. I will eventually have to dig in around the sides of the road and install a french drain or something that leads into my property before backfilling the road shoulders with river rocks or pea gravel.



Geoff Lawton's "Greening the Desert" project in the Dead Sea area of Jordan used road runoff as a source of harvested water. Usually you'll want to put a bio-swale in to catch the water coming off the road to help clean it of toxins (swale filled with woodchips and/or trees/shrubs that serve a filtering role). That road is slightly higher than your property if water is pooling to one side. I know Brad goes into water harvesting from roads in Vol. 2 of his books (Earthworks).
 
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