One of permaculture´s most famed and acknowledged contributions to sustainable land management and ecologically sound agricultural practices are swales. From Australia to Finland to South Africa, thousands of permaculture practitioners from around the world have taken their laser levels, A-frame levels, and Bunyip water levels to map out the contour lines across the landscape that holds them. Once stakes have been placed across the contour lines across the land, either a backhoe, or a strong back and a hoe carve out shallow ditches that are meant to hold water in the landscape, prevent erosion, and accelerate the natural succession towards richer topsoil and more vibrant landscapes.
There is absolutely nothing more satisfying for a permaculture farmer than to walk through his fields after a 2 hour long downpour and see puddles of water standing still in the ditches/swales that he had previously dug out. That water, which otherwise would have run over the landscape taking with it fertile topsoil for future crops, is now slowly infiltrating into the land, adding to the long-term resilience of the land to withstand drought. At the same time, the delicate layer of topsoil remains intact and, like a sponge, soaks up the excess water that is soaking into the land.
The Problem with Swales
Despite the obvious benefits of swales to land and water management, anyone who has built their own swales also knows that they can be a major challenge to maintain year in and year out. As excess water and soil accumulates along the contour lines of swales, they quickly become a hotbed for production and pretty much anything will quickly grow there. After a wet spring, you´ll find that your neat contour ditches now resemble a mini-jungle as the ditch itself is literally engulfed by the growth of organic matter.
While swales will continue to capture water, when left alone and not cared for, they do quickly fill in due to the massive growth of biomass. Those of us who have wanted to maintain the full “water-catching ability” of swales know that it does take a heavy dose of work to maintain the swales free from plant growth. At least twice during the growing year, it is necessary to go through the system of swales with a hoe and shovel to clean out the accumulation of organic matter and soil that threaten to fill in your expert water-catchers.
Not only is this hard work that is labor intensive, but it also requires frequent upturning of the soil which ironically leads to the diminishment of the very soil food web that your swales are trying to protect.
Might there be a way to use swales as a short-term solution to protect your soil and manage the water entering your land while slowly transitioning to a longer term answer?
On Contour Hedges or Tree Lines
A thick row of densely planted shrubs or trees is just as capable of stopping erosion and aiding the infiltration of water into the landscape as swales. The problem, of course, is that it takes time (often several years) to grow trees or shrubs into a decent enough size where they will be useful for that purpose.
One of the guiding principles of permaculture is to always think in the long term. As the Anishinaabe Indigenous People remind us, it is necessary to think seven generations ahead for any action that we undertake. In the case of swales, maybe we should begin to ask ourselves if our great-great-grandchildren would want to inherit the task of digging out the swales we originally put in, year in and year out.
Instead of burdening future generations, and your aging back, with the task of swale maintenance, a longer term solution would be to plant a hedge or tree line on the downside of your swale at the same time you dig the swale. Many quickly growing species can grow thick enough and tall enough within 2-3 years to essentially replace the functions that your swales were providing. Maintaining your swales for 2-3 years is much preferable to maintaining them for a lifetime.
The trees or bushes that you plant on the downside of your swale will also benefit from the excess water and fertility that accumulates along the contour lines of your swale. If you live in an especially wet climate, it might make sense to plant water-loving or water tolerant species such as elderberry or alder so that they can take full advantage of the excess water they will have access to.
The Multiple Functions of On Contour Hedges
As with all things in permaculture, it is important to always attempt to assign as many functions as possible to any element that you include in your overall system design. In the case of on contour hedges, they essentially assume the functions of the swale; helping to avoid erosion and infiltrate water into the landscape. Excess rainwater will run into the on contour hedges, spread across the contour line, and slowly infiltrate into the landscape.
Additionally, hedges offer other functions to the system that swales do not. Hedges add abundant organic matter that only further increases the ability of the soil to hold water through improving the fertility and organic matter content of the soil. You can choose to plant certain quick-growing nitrogen fixing species for your on contour hedges such as alder and black locust. These species respond well to heavy pruning which will give you an abundant source of mulch material while also fixing enormous amounts of nitrogen in your soil.
Of course, you could also choose to plant food-bearing species in your on-contour hedge, including shrubs such as sea buckthorn (also a nitrogen fixer), dwarf mulberry (a great food source for chickens and easy to prune), goumi (nitrogen fixing and delicious berries) or even small fruit trees interspersed with nitrogen fixing shrubs.
The Transition Towards Sustainability
While swales certainly are an important contribution to sustainable land management, our experience shows that they are best utilized early in the succession phase or early in the process of restoring the ecological resilience of the landscape. As with all things in permaculture, searching for other solutions that offer longer term solutions with more beneficial functions to the overall functioning of the landscape is essential. Transitioning from swales to on contour hedges might just be a strategy worth exploring if your back is telling you that it has had enough of cleaning out your swales.