We use affiliate links. If you purchase something using one of these links, we may receive compensation or commission.
In today’s world of rapid development and declining resources the term waterwise tends to come up in many agricultural discussions. Swales are a practical way to help manage your water on any project where the technique is applicable.
What Is a Natural Swale?
A natural swale is basically any shallow channel with sloping sides. A permaculture swale is a shallow channel with sloping sides built at a 3:1 ratio, which is three times wide as it is deep. This is built on contour. Building on a contour is the practice of tilling land on sloped lines to help conserve rainwater and reduce soil erosion. Let’s look at the basic functions of a swale.
What Is the Function of a Swale?
First by helping you channel your rainwater where you want it. With a permaculture swale usually your first objective is to conserve and direct the available water. The strategies vary in different climate zones, but the general core principle is the same.
In short, the function of a swale is to channel your rainwater, retain the water, help it to infiltrate the surrounding areas in a sensible manner and sometimes even for the filtration of various pollutants. Swales equal water diversion, retention and filtration.
What Is the Difference Between a Berm and a Swale?
In most cases a swale is accompanied by a berm. A berm is a mound often built from the material excavated from digging the swale.
Dry Climate Swales
In a dryland climate, your swales will be further apart, and usually the swales are used for planting things like trees or other plants that require higher moisture levels. When in an area with more rainfall and humidity the swales are closer together, and the berms are then planted in the same manner as the swale is on dryland.
Swales can be combined with the techniques like hugelkultur also known as the mound culture. This is where the bulk of the berm is made with decaying wood and other comfortable materials before being covered by soil.
Tropical Climate Swales
In the tropical Caribbean where we live, I use a system of closely spaced swales and berms. The swales are partially backfilled with decaying wood and the whole area is heavily mulched with various leaf matter. So not only do these swales help divert the rainwater, they also soak up a fair amount of water like a sponge. This wicks slowly back to the adjustment berms.
These swales also house an immense amount of bacterial and fungal life helping to restart the surrounding ecosystem. This decomposing matter in the swales also turns into decent soil after a few years, at which point the swales can be scooped out, and the soil added back to the surrounding berms. Then the swales are repacked in the same manner, and the process begins again.
Can You Plant in a Swale?
When considering what to plant in your swales and berms try to use a combination of nitrogen fixers, erosion control plants, and other multifunctional flora. Remember since you have just dug up your soil you need to restore its biology as rapidly as possible and protect against erosion.
Generally, any site prepared with a swaling system has greatly improved its abilities to manage and conserve its water resources. The restorative properties of such systems are many.
There is a wide array of information available today on permaculture swale design, and construction. It can be well worth utilizing these tried, and true waterwise strategies.
