Swale Pathways

Feb 12, 2014

Hobart is Australia’s second driest capital city (Adelaide’s first) so catching and storing water is often on my mind. Annually we get approximately 615mm, most of which arrives in the cooler months in and around Winter. During Summer time our soils will dry out so ferociously that some soil types (including ours) will form cracks big enough to stick your hand a good foot into them. When we first bought our place in mid Summer 2012 we walked across the lawn-scape and had to be careful not the slip into the cracks and twist our ankles – seriously, they were that big.

So as soon as we could we shaped the land to catch, slow and sink water into the soil in every possible way. First up, we had an excavator come through to terrace the back half of the block. All the terraces are angled slightly back on themselves to guide the water into the slope rather than letting it slide off the slope. On top of this we designed the key artery pathways to be swale pathways (the blue lines shown below). These are placed on the inside of the terrace where they catch all the excess water that the terraces guide back into the slope.

earthworks

But lets back up here a minute and make sure we’re clear on what a swale actually is. A swale is a ditch dug on contour – this means that water is not draining in one direction, instead it spreads evenly across the slope and sinks into the soil. Traditionally, the earth that is dug out is placed on the downhill side and planted out with with a mixture of perennial and annual crops (but always perennial to ensure that the earth is stabilized with good long-term root structure). As we’ve made deep terraces, our garden is a variation of this, but still receives the same benefits – water in the ground.

swales-trad

A diagram of a traditional swale system

A hot tip is to remember that you always need to plan for flood and have an overflow system, even when you live in the second driest capital city in Australia. This can be a pipe or drain which directs the excess water to another swale, pond, orchard, dam or storm water drain. What system you choose will all depend on where you are and what is appropriate for your property. Eventually (we haven’t quite finished it yet) our overflow system will be directed into a series of ponds and additional swales which will end up in our orchard which we’re planting out in the front half of our block this Winter.

swale colllage

It rained as soon as we dug the swale which allowed us to see the amount of water it actually holds (left) – a lot! We then lined it with cardboard to prevent any unwanted plants growing up and filled it with sawdust (right). When it rains no muddy puddles form, instead there’s just soft spongy sawdust paths – nice!

2014-02-05 08.13.12

January 2014, the swale path has now settled in and the young food forest (left) and tomatoes (right) are loving it.

It’s now just over one year since we’ve moved into our home and the section where we’ve applied these water storing techniques is largely under cultivation. There’s still lots to do, but it’s happily unrecognizable from this time last year. The great thing about this water system is that it’s PASSIVE, now that it’s in place our work load has been reduced. We’re still going to install drip line irrigation, but through establishing this passive water framework and mulching throughout the warmer months, we’ve drastically reduced the need for irrigation and that’s a major step in the right direction in creating a stable and resilient system – yay!.

Dec-Sep backyard progress

An older photo (sorry), it’s looking fairly different now with lots of crops growing everywhere!

So, do I need an excavator to have swales? I hear you ask.

No, absolutely not, is the heart felt answer. As someone who rented for over 10 years and lived in 25 houses I’m passionate about affordable, transferable and effective strategies which can be scaled up or down.

Swales can be hand dug and one metre long. Always come back to the function it’s performing which is simply to catch and store water in your soil. You can obviously do this on small or large scales, while renting I would often dig swale paths with my mattock as seen below.

george st swales

Rental property, 2012. Narrow swale paths with ag pipe (a pipe punctured with holes throughout) – we directed our laundry water or garden hose into this pipe

As these particular swale were quite small, we increased their capacity by laying ag pipe down which we could then plug a hose into from a laundry and bathroom. Using grey water to irrigate crops is technically not smiled upon. However please keep in mind we put no nasty chemicals in there and alternated where the water was directed to, so there was no build up of any nutrients which can affect soil health. On top of this no water touched the surface or leaves of plants – it headed straight underground. In our experience when managed properly this is a great way to return water to the soil instead of sending it down the storm water drain.

So there you go, swale paths are for all shapes and sizes and can play a clever and effective role in catching, storing and sinking water into our thirsty landscapes.

Fabulous resources you should check out

*Your blogger is Hannah Moloney: Co-director of Good Life Permaculture and lover of all things fun and garden-esk

your thoughts:

6 Comments

  1. Peter Gillam

    Hey Hannah,
    Your swales look great. And I really dig these slotted pipes as they reduce the risk of flooding a neighbour.
    My dad sends water out of his down pipes through a similar slotted pipe systems ie. a slotted pipe with a champagne cork in the end. When the pipes are at capacity, the excess roof water goes to the drain. The rest of his roof goes to a tank. This way he gets 100% utilisation of his roof water without the need for several tanks or tricky plumbing.
    This approach could be used to flush the grey water through your slotted pipes and soil every now and then. I’ve known grey water get pretty chunky with microbes and block slotted pipes which would be a bit of a disaster if they are buried.
    Great work,
    Captain Rain-Garden

    Reply
  2. Hannah Moloney

    Hi Captain Rain-Garden :-),

    Yep, I agree with you – it’s a good idea to be able to flush grey water pipes out when using the slotted ag pipe. The one above was for a short term rental so it was quick, simple and effective – worked a treat! But for something more permanent I’d be wanting to have either a grease trap or reed bed to filter all the chunky bits and slime that builds up.

    Cheers!

    Reply
  3. Claire

    Hi Hannah, I wanted to let you know that your blog has been very informative and inspirational…. I’m thinking ‘swales’ right now and wanted to get a feel for the scale of them in a domestic setting. Your blog came through again 😀

    I also wanted to wish you all the best with the birth of your baby.

    Cheers
    Claire
    (who did a composting program with you in Lenah Valley and now has a wormfarm, tumber and bin going strong… the worms are our favourite!)

    Reply
    • Hannah Moloney

      Hi Claire!
      Wonderful to hear form you and that your composting is going strong, that’s makes me so happy. And I’m stoked that this blog is useful, that was the whole idea. Keep up all your greatness and thanks for your kind words – the babe isn’t far off now!

      Reply
  4. Simone

    We’ve got a gentle slope that we’d like to convert into a terrace for growing fruit trees and some under growth plants using this swale pathway system. Do we need to reinforce the berms and would that be best with wood that breaks down over time as the plants get established? Also do we build up the berms with the excavated soil or will it be more like a slope and a swale similar to yours?

    Reply
  5. Simone

    Also thank you so much for this article! It is very useful and informative.

    Reply

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