Week 2: Swales

Water is one of the most important resources in an ecosystem: everything depends on it, but it can also be extremely damaging. When creating a permaculture design, it is the first thing that needs to be considered. In order to properly manage and use water to its full potential, following the Permaculture Principle “Catch and store energy”, one of the most common and valuable tools is the swale.

A swale is a method of shaping the landscape to increase water catchment and storage, allow greater and slower water distribution, and prevent runoff and erosion. Swales are iconic elements of permaculture, so we felt having one was essential for our Showcase Permaculture Garden. Since the site is slightly sloping as well, it would be important for stopping and slowing the water (and all the organic matter, nutrients, and soil it carries) running through.

Swales consist of a shallow trench dug along a contour line where the base of the bowl is completely level. That way, water that enters will distribute evenly along the swale instead of accumulating in one area. It then seeps into the ground and percolates through the landscape underground. The soil removed from the bowl is piled on the downhill side to form the berm of the swale. This is seeded with plants – either naturally with seeds transported by the flowing water, or by hand. The plants are often deep-rooted, usually trees, and increase the water catchment action of the swale, as well as stabilizing the landscape and preventing oversaturation.

swale-cross-section

Swale Diagram

The first step to building a swale is to decide its placement and map the contour. We placed ours near the top of our landscape where it will be the most efficient. We were very lucky that day to have the help of a friend from our Permaculture Design Certificate: Mathieu, a perfectionist engineer with a laser level that we could use to measure contours quickly and easily.

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The swale with the marked contour line and the topsoil removed

The next step is to remove the topsoil and place it grass-side down on the down-hill side; this forms the beginning of the berm. Then, we dug downward to form the base of the swale. Once we had one area dug to an adequate depth, we could create reference points of the same depth all along the rest of the swale using the level, so that the entire base is even. Next, the sides were dug down at an angle to prevent erosion, and the soil piled onto the berm.

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The completed swale!

Once the swale was built, we planted the berm with a mix of different seeds we had left over and mulched. It isn’t complete yet, the bowl still has to be filled with bark chips and will serve as a path, and we want to eventually have trees and shrubs planted on the berm, but garden construction is officially underway! This is the first major change we have made to the site and being able to see progress is exciting.

Next step: Sheet Mulching.

Sources

Engels, Jonathan. “Why We Use Swales and How To Do It Appropriately.” Permaculture Research Institute, 31 Mar. 2017. http://www.permaculturenews.org/2017/03/31/use-swales-appropriately. Accessed 26 May 2017.

Swale Diagram Image Source: https://www.odicis.org/water/water-infiltration-diagram

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