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Swales for Drought: Is the Hype Real?

Posts: 985
Location: Western Washington
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I'm thinking about having swales put in on a gently sloping 16 acres property. I've heard all sorts of fantastical things about them increasing water retention and helping during drought. I'm willing to give it a shot, as sometimes things that seem too good to be true really are true.

What are your experiences with this? A friend of mine (who's also a member on here) told me that she visited a site from the Conservation Corps built during the 30's in Arizona. She said it wasn't as good as it was made out to be, as the site was built at the base of a mountain range (not often included in discussion and photos) and therefore benefited from that runoff as well.

What are your thoughts and experiences with this? I would mostly be planting trees on the land
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Location: Haida Gwaii, British Columbia (7b)
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I’ve just read a whole shwack about “moving water across your land” in Ben Falk’s The Resilient Farm and Homestead so I’m all pumped to build some swales of my own.

The purpose of swales on contour, is to slow and spread the flow of water down a slope. When water builds against a swale, it will slowly permeate back into the ground, as it flows across the ground - directed by the contour of the swale. In theory they need to be positioned to catch the down-slope flow of water before they’ll be very helpful. Does the slope catch a lot of water?

Adding some ponds to store water into your earthworks/swale system might work? The two seem to be often intertwined!
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The old swales on my land are very much like what your friend experienced. For me, they were installed in 1954 when two gales and a hurricane came back to back to back, and this being a potatoes farm, caused all that water to run down the hilled rows and cause severe erosion. Today, in this county, the swales installed during 1964 remain everywhere, yet on my farm they caused more damage than good. They never terminated the swales right, and so all it really did was divert water, and put erosion where they stopped.

But these were old swales, and this is Maine. We get a lot of water here, and in fact, over the last 20 years, we are getting MORE water, about 5 inches more of rain per year than 20 years ago. We also get a lot of snow, and with spring snow pact melt, it means our swales here get absolutely overloaded with water. We cannot just plan for 5, 10, and 50 year rain events. Spring thaw might be the equivilent of a 100 year flood, and that might happen every five years (a winter with a lot of snow).

But that does not mean I do not install new swales. I do, and have installed several miles of new swales on this farm, and intend to add more. For me now, I use a lot of erosion control rock check dams, and terminate the swales so they are more like sediment traps. So it is kind of a two prong approach. I am doing everything I can to prevent erosion, but I also know I am inevitably going to get some, and when I do, I know I can clean out my swale ends and at least capture, and reuse, the soil that has been eroded.

This was a swale end, a sediment trap just after construction in 2017, and will attest wholehearily that this works. The swales installed in 1954 have all been removed.

Just out of sight in the lower, left coner is a rock check dam. Then you see the swale formed as it goes down to what is a rock-bottomed field access ford. Then you see another rock check dam, marked by two grade stakes so that I can stay clear of it while bushogging high grass. Quite a ways farther still, you see another rock chck dam. Between the staked rock check dam, and the rock check dam farther down, is the sediment trap area. I designed this myself, but was checked and approved by the State of Maine USDA Soil Engineer, and was given a grant to do this swale work under EQUIP Conservation funding. Sadly, the payout was only $500, which is far less than what its real cost was, but it was done right. We had severe rain all spring, and the rock check dams, and sediment trap, are working as they were designed.

As a side note: this drains about 5 acres of a 9% slope of high erodable gravelly loamed field.

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Swale Sediment
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Location: Central Texas USA Latitude 30 Zone 8
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James Landreth wrote: A friend of mine (who's also a member on here) told me that she visited a site from the Conservation Corps built during the 30's in Arizona. She said it wasn't as good as it was made out to be, as the site was built at the base of a mountain range (not often included in discussion and photos) and therefore benefited from that runoff as well.

The swale was probably installed to mitigate flooding run off from the mountains.  We have mainly installed earthworks to mitigate flooding but we have certainly seen benefit from them in increased plant growth.  If you don't have surface run off or flooding, there's probably no benefit to installing swales, as they would have no water to collect.  

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Location: La Mesa, Cundinamarca, Colombia
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James, it really depends on your climate and the possible extremes of it. Also the size of the catchment area above your land matters.

We started of with swales, to switch to terracing later. Swales are tree growing systems, and on terraces you can grow anything you want.

We have designed our system to minimize erosion and maximize water infiltration. That's because we cannot afford to loose the excess water during the wet season. We need that in the ground. But we also designed all these systems for that once in a 100 years flood, where we get way too much rain to keep on our property. For that we need swales as water transport channels, to move it down bit by bit as calmly as possible. So you can find rock covered stairways everywhere on our land that double as waterfalls in severe weather events.

Swales are useful if installed for the purpose they can have: water control. I hope this is helpful.
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Great question James. I too was a skeptic until I saw swales in an arid climate working with my own eyes...

A couple of years ago I took a Social Permaculture workshop at Quail Springs Permaculture in the arid Cuyama Valley in Southern California. There they have a series of swales & berms (installed by Geoff Lawton, if I'm remembering correctly) on pretty much what amounts to beach sand "soil" in the desert.
Downhill from their communal kitchen yurt they have their community greywater emptying into a small kitchen garden, then downhill to a willow grove that they use for basketry weaving workshops, then downhill of that, the rest of the greywater makes its way through several swale & berm food forest systems.

When I was visiting, the person who had originally designed & installed the food forests had left a few years earlier while some younger folks had moved into the community.
One day, I was wandering around in the lowest food forest swale & berm system, farthest away from the yurt & water source. I was glancing around on the ground & saw some almonds. There were many of them. I opened & nibbled on one of the almonds & it was by far the tastiest almond I'd ever had in my life!
I walked up back to the kitchen yurt & grabbed a bowl, walked back down & started collecting the fallen almonds. I went around to all the almond trees & shook them a bit, collecting more almonds. These trees were not being actively watered by any hoses, drip systems, nothing.... except what the swales were slowing, spreading, & sinking from greywater & very little rainwater. Reminder: greywater that had already passed through a kitchen garden, willow grove, & swale & berm food forest! It's fair to say that at this particular point in their life, they were being pretty much completely neglected (by humans) & were feral fruit trees.

I placed the bowl full of almonds in the kitchen. When dinnertime rolled around the 20-something-year-old community members of Quail Springs, who'd not been around during the time of the swale & berm food forest installation some years earlier, asked aloud "Where did these almonds come from?!" I smiled & told them that I had gathered them from the swale & berm food forest located farthest from the yurt. They were blown away; they had no idea they even had any almond trees on site, LOL!

Having been told my whole life how water intensive almond trees are & how irresponsible they are to grow in Southern California, my paradigm had just been totally shifted on that. Yes, I agree it's irresponsible to divert massive amounts of water from other people's watersheds for industrial monoculture (almond) production. However, I have now seen with my own eyes a functioning desert swale-&-berm food forest system that passively collects rainwater & greywater & integrates them into a diverse multi-strata agroforest system & works very well, even when utterly neglected in an arid climate.

In his Permaculture Design Courses, Bill Mollison mentioned that one of the things that inspired him to design systems with swales was the mimicking a feature of a natural process: when glaciers / ice sheets recede, they often leave behind swales on the land as the changing seasons cause the ice to recede in a pulsing action. Thus, swales are in fact one of nature's patterns in many landscapes.

Human-made swales are great example of implementation of the idea Brad Lancaster got from a person successfully re-greening arid areas of Africa: "First, plant the rain."

PS- Nice meeting up with you a couple of weeks ago James; I wish you well on your project with Gerry
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