First and foremost, most swales are tree-growing systems, meaning that you use swales when you want to grow your food forest.
A swale is a shallow trench laid out dead level along the land’s contours. The earth dug from the swale is piled on the downhill side to make a raised mound or berm. Following this, we plant trees or other crops on the mound (berm) on the downhill side of the swale or just below it.
Surface water and rainwater run downhill into a swale, spread out along its length, and slowly percolate into the soil, forming a lens of moisture. The trees can then take advantage of this soil moisture during dry periods.
Therefore, swales are not moving water, rather they’re intercepting a large amount of rainfall, then they fill up and infiltrate water - slowing, spreading and sinking it.
Now, with that said, there are certain situations where you wouldn’t want to build swales, and it all depends on your slope, soils, rainfall amount and distribution, type of management, your resources…
Swales are not, of course, a one-size-fits-all solution, even David Holmgren, co-founder of Permaculture doesn’t have swales in his permaculture orchard, but…
Chances are, if you have a blank canvas and acceptable terrain then, looking toward the future and climate change, you’ll be better off if you build water systems that can stand unpredictable weather.
- How would you design swales on your property?
Here’s something I found online:
Here you can see a property transformed into a permaculture system with a food forest and three main swales.
Geoff begins the design process by looking for the longest contour line on this property first - on this image this is the middle line.
You see, the main principle of water harvesting is to take water on the longest path over the most distance and, once you find the longest contour on your property, you have done exactly that.
Interestingly, this line/contour intersects many creek gullies or valleys that are perfect locations for a pond/dam, so once this swale is in action, it’s not just taking the water on the longest path over the most distance, it’s making many connections between the ponds/dams.
This is your main swale and other swales are designed in relation to this one. In Geoff’s case, the bottom swale near the house is connected to the pre-existing dam and acts as catchment, while the top one is also hydrating the landscape, harvesting the water (swale) and storing it (ponds).
Right, now we have three food forest contour lines dividing this landscape, harmonizing with the landscape itself - harvesting water, rehydrating the landscape and boosting the overall resilience of the farm…
See, that was easy! But what if you want create something smaller, something like a permaculture orchard that has uniform rows?
Well, I’ll let you into a secret that I learned from David Holmgren about how to design one in the next email.
Until then, let me know if you have any questions about swales.