Swale Contour Basics

Posted by admin on Jul 16, 2010 in Permaculture, Water Harvesting | 0 comments

A while back when we made our first DVD on harvesting rainwater to drought proof your property we first came across this term “Swale.” What does it mean exactly and why do Permaculture people advocate its usage? If you asked Geoff Lawton from the Permaculture Research Institute what it meant he would give you the standard definition:

“A swale is a water harvesting ditch on contour with a soft mound on the lower slope.”

If that definition went over your head – you are not alone. The swale ditch must be excavated and perfectly aligned to follow the natural contour of the property.

It can be as long or short as you like. Some swale systems can run for many miles. It’s function is to slow the flow of water. To hold water for as long as possible, perfectly level for as long a time before it runs away.

Most engineering ditches deal with getting rid of water. Think of guttering on your roof or on the side of roads.

In Permaculture theory the principal is to slow the movement of water right down. To keep the flow moving slowly and allowing it to soak gently into the surrounding landscape and rehydrate the aquifers.

It can take a lot of active field work to become proficient in reading the rhythms of the landscape – but the principal is sound and if you use it cleverly on your land it can rehydrate a sizable property and replenish underground water springs and be a clever way to reforest a trashed environment with say – a food forest system that adds value, beauty and natural abundance to your property.

Its no wonder that many Permaculture consultants are asked to walk over farmland, define the best place to site a swale that connects to properly situated dams that have a spillway that directs water where it can be put best to work.

A swale to work best must be sited exactly on contour. Hiring the services of a laser level might be an easier choice to peg out the natural contour on your property but knowing where to site the swale and dam system is an art that takes many factors into consideration.

Australia with its long periods of drought, followed by heavy downpours sees most water run off the landscape very quickly leaving the substrata still dry.
This is where the landowner during periods of drought should plan their water harvesting infrastructure very carefully to make the maximum use of every drop of rainwater that falls during the big wet periods.

At Mulloon Creek near Canberra Australia, Geoff Lawton built 2 kilometers of swales that feed into a network of dams that help drought-proof the valley.

The swales help to recharge water back underground where it can be “banked” for later usage during the inevitable dry periods that can last many years as well as feeding back into the neighbouring creek system sending water down steam to other farms.

The advantage of swales is that you can also plant a food forest system on the lower mound side where the water will gradually seep away. A Food Forest will build you a canopy of trees, reintroduce native flora and fauna and generally stabilize fragile eco-systems.