The term ‘swale’ originates in permaculture. It is a shallow channel or trench that is build on the contours of the land and the goal is to collect water. The soil that comes from the channel is used to create a platform beside the swale and it is covered with as much mulch as possible. When plants and trees grow on these platforms, a natural diversity is created.
On flat landscapes in warm climates the platforms are placed on the south side. This is because trees provide shadow and in this way, they can prevent evaporation of water. In cold climates, it is the other way around and on slopes the platforms are placed at the bottom. In this way, the water can be stored longer and the platforms will slowly be fed by water. Due to wind, rain and time a swale will clog and this creates a really rich soil.
Connections between ponds
A swale can also function as a connection between ponds. This connection can be placed, for example, next to a vegetable garden, an edible garden forest or an orchard so it can function as a natural irrigation. But, a swale can also drain water in areas where there is (temporarily) too much water. So, a swale is not like a canal in which there is always water present. When installing a swale, it is important to look at the contours of the land. In the Netherlands, these are not always present, but many shallow landscapes do have a little slope, even though it is only one or two percent.
Natural and diverse principle
A swale is actually a natural principle that can often be seen in nature. Especially in the Netherlands, with its delta landscape the swales are very present. When looking at the history of a river, platforms are created over the years due to high tide and low tide. This effect causes that the shores and soil behind the platforms are the most fruitful. A swale can be used in every climate. In deserts, for example, it is the best solution to make dry areas green again. In this situation, the swales are made bigger than usual to catch as much water as possible. This effect can be beautifully seen in the film ‘Greening the Desert’ by Geoff Lawton.
Swales can even be used in cities. The film below explains how the ecosystem of a tree works and how a problem with a water system in a city is fixed. The situation went from water floods after a rainy day to using the rainwater for irrigating the trees and plants in the city. In short, the city became greener, the problem is fixed, it saves money and the citizens are happier. In the second film, you can see the project and the citizens in more detail.