Zaytuna_farm-Swale

Understanding Water Part 2: Working with Flow

Zaytuna_farm-Swale

Copyright Ingrid Pullen Photography

In my previous article, we explored how the basic principle of water is that of flow, and so in order to work well with water it is important to be aware of what the flow is and where it is going. On a practical level, this involves some basic observation and a wealth of techniques which can be used to help utilise water to the advantage of your garden or farm.

One technique that is quite well discussed in the world of permaculture, though in my experience relatively unknown anywhere else, is the use of swales. Here I will share some practical tips for creating swales and optimising the flow of water.

The five-fold path to water wisdom

One of the most useful references I find is Toby Hemenway’s book Gaia’s Garden (2), in which he recommends five practical steps to conserving water: high organic-matter content, deep mulching, locating plants according to water needs, and soil contouring (2). This article will concentrate on soil contouring; however, it is prudent to bear the other four in mind during your design process, as part of the ‘multiple elements for each function’ principle.

Swale scale

A swale is, at the most simple level of explanation, a ditch which runs level with the contour of the slope of the ground, with a small hill of earth on the downhill side. The idea utilises the ‘Three S’s – Slow, Sink and Spread’ (1) idea: when water is running down the hill, the ditch catches it, slowing the flow. Much of this moisture gets pushed below the earth by the hill, sinking it. Over time this process will continue spreading the water through the whole lower level of the hill; eventually creating what’s known as a ‘lens’ of moisture which will significantly increase the fertility of the soil above (2).

These can be of any size and scale: from a hand-dug one to aid the fertility of one vegetable patch in your garden, to the nation-wide re-landscaping projects implemented by US President F.D. Roosevelt in the 1930s as part of the Civilian Conservation Corps (3), some of whose work can still be seen to be making a difference today, such as the swales made famous by Geoff Lawton and Bill Mollison which have created a lush grassy oasis in the Arizona desert (4).

The most important thing when you are making your swale is that the ditch is on contour with the slope of the hill. This is the way to ensure that water conservation is at its maximum. If your hill is an awkward or very steep slope, it may be beneficial to re-landscape the hill itself before digging the swale. This can be done with a pick-axe and a friend or two if you are working at a basic level. If you have a large area to deal with, it may be better to use a mechanical digger.

A-frame: how to make one, and their importance

Whatever scale you are working at, the most useful tool you can have in order to ensure the accuracy of contour level is a very simple contraption known as an A-frame. This uses gravity to show you the plane of your swale so that you can ensure that it stays on contour.

A-simple-A-Frame.-Photo-by-David-Ashwanden

A simple A-Frame. Photo by David Ashwanden

In order to make one of these you will need:
• 3 sticks of any length between 1 and 2m, of straight and sturdy wood such as bamboo, or light metal
• Some string
• A heavy weight such as a rock or plumb bob – or even a beer bottle will do
• Coloured electrical tape or something else to mark it

Method:
Tie the sticks together in a triangle shaped like an ‘A’. Measure the stick which goes across the centre, and mark the middle of it with the electrical tape. Take a length of string which stretches from the top of the ‘A’ to the stick in the centre and cut it to size. Tie one end around the weight, ensuring it is secure. To make sure the centre line is accurate, you can try standing the A-frame upright in a place which you know is flat, and marking where the weight hangs down. Then reverse the A-frame so that the leg which was on the right-hand side is on the left-hand side, and vice versa. Mark where the weight is hanging now. The centre is halfway between the two marks. For even more accuracy, you can attach a spirit level bubble to the centre stick as well.

Ready to shape

Now that you have your A-frame, you are ready to start swale-ing wherever you like. As mentioned, the method depends on the scale of your project. I shall share my most recent swale experiences that can provide a reference, and then you can either scale up or down depending on what your needs are.

Swale up the mountain

In Spain, the idea of contouring the land has been in use for at least a thousand years (see for example 5). During my stay at La Loma Viva permaculture project (6) I helped to revive this tradition by shaping some of the steep mountain slope into a series of fertility-encouraging ditches.

Here is what we did:

• Clear existing vegetation

If you are going to dig somewhere, it’s far easier to start with the bare earth rather than having to deal with pushing your tools through plant matter. We were shaping a fairly large area – i.e. much large than a home-scale gardener would be using; though small compared to the scale of the farm, which covers around 7.5 hectares (6) – I would say the slopes I worked on were around 0.5 of a hectare altogether. This means it was more efficient for us to clear the vegetation using a motor-strimmer. When deciding whether or not to use machines it is always prudent to consider how much human-power it will take to do a job manually; if the amount of energy expended on feeding the humans so that they can work comes to around the same or more as that used to power the machine it may well be more environmentally friendly, as well as more efficient for you, to use the machine. It is also a good idea to think about where your materials will end up. We used all of the cleared plants to be the ‘green’ part of a hot compost pile. In this way, you can maximise your results and utilise the ‘multiple elements for each function’ principle.

Hot-(steaming)-compost.-Photo-by-David-Ashwanden

Hot (steaming) compost. Photo by David Ashwanden

• Make the ground as even as possible

If the land you are working with is exceptionally bumpy it may be beneficial to even it out. We did this using a mechanical digger to pull the earth from places where it was high to places where it was low. The advantages of this are: it makes the work a lot quicker, it makes the ground easier to manipulate as the earth is already loosened by the digger, and the fact that you are always using the same tool means it is easy to ensure accuracy and evenness.

If you do decide to use a mechanical digger, it is a legal requirement in most countries to obtain a certificate saying you know how to use it. It probably goes without saying, but if you do not know how to use one, it’s not really a good idea to try without training.

• Dig the ditches

Next comes the actual swale-digging. For our scale, the ditches were around 30cm wide and 10cm deep. Using spades and/or pickaxes, dig out the ditches, placing excess earth on the downhill side to form the berm. You want the ditches to be as smooth as possible to ensure that the swale stays on contour. Place any rocks you dig out in a pile to one side – you can use these to fill the swale(s) with once they are complete.

• Drainage Plan

Every swale needs one very important feature: the overflow ditch to carry excess water out of the swale. The drainage ditch is not on contour: these are some of the rare places where water is encouraged to flow fast to get it from one place to another. If you have enough slope these ditches can lead to the next swale down the hill to help to fill them. Drainage ditches can even double up as paths when there is no water flowing along them.

To dig the drainage ditch, you need to make sure that it is deeper than the swale from which it will carry water. It cannot be too vertical as the water flowing down it will flow too fast and erode the ditch, so you need to make it fairly long. Between two swales we made two drainage ditches of around 20cm wide to connect the swales, and carry overflow water from the bottom swale into the field below it.

Swales-and-ditches.-Photo-by-David-Ashwanden-

Swales and ditches. Photo by David Ashwanden

• Check your angles and move the rocks

Remember as you dig to keep using the A-frame to ensure you are still on contour. Once you have more or less finished the ditch, you can walk along the whole length of it with the A-frame, neatening up any stray angles. You will probably have to repeat this process a few times (especially if you are generally very precise in your work) as you continue making minor adjustments. Once you are satisfied with the level and angle of the ditch you can place rocks in the parts of the swale where water will first enter and leave it. This will help all the shapes you made to stay intact and avoid erosion. It’s also a good idea to line the drainage ditches with them for the same reason.

• Patting down the berm

The berm is the little hill on the downhill side of the swale which will filter water through it and thus increase fertility in the soil below. As it will be acting as a filter, in general, it is advisable not to walk on the berms once the swale is complete, so that the soil does not compact too much. However, as you are making the swale you should be compacting the berm, to make sure that it stays in place. The easiest way to do this is by walking up and down on top of it and pressing the hill into shape with your feet. Doing this in time to swale-themed music is optional. You want the berm to be, as much as possible, the same height all along the length of the swale so you should incorporate levelling out into your patting-down. Take earth from places where there is too much to places which need a little more height, and keep gently compacting and shaping it as you go.

• Optional Tree-planting

Many advise (see for example 2) planting trees or strong-rooted bushes in the berms to help them to hold their shape. If you are digging more than one swale you can also plant trees on the slope in between them to make use of the water.

• Fill her Up

Now you have a beautiful on-contour ditch with a berm on the downhill side – a new swale! To check that the swale will do what is planned of it, ideally you now want to fill up the whole thing with water and monitor what happens. Pour the water in from the place where it is most likely to come, and be careful to not let it fall too much in any one part of the swale, or you could compromise the evenness. The easiest way to fill up the swale is probably with a hose.

Water-filled-swales.-Photo-by-David-Ashwanden

Water-filled swales. Photo by David Ashwanden

• Observe and Interact

Now you have your finished swale you can watch it subtly changing the fertility of the land around it. It is important to observe how th eswale responds to the first few rainfalls – you may have to do some readjusting here and there, and possibly a little bit of rebuilding. The water will always show you which way it wants to go – learning this can be one of the most fascinating adventures you can embark upon.

References
1. Haworth, C, 2015. ‘Understanding Water part 1: the Theory of Flow’. Permaculture News, 30/3/2015. http://permaculturenews.org/2015/03/30/understanding-water-part-1-the-theory-of-flow/
2. Hemenway, T, 2009. Gaia’s Garden: A Guide to Home-Scale Permaculture. Chapter 5; Catching, Conserving and Using Water. Chelsea Green: Vermont
3. Maher, N.M, 2009. Nature’s New Deal: The Civilian Conservation Corps and the Roots of the American Environmental Movement. Oxford University Press: Oxford
4. Geoff Lawton, 2014. ‘Discovering an Oasis in the American Desert’. Permaculture News, 11/10/14. http://permaculturenews.org/2014/10/11/discovering-oasis-american-desert/
5. Haworth, C, 2013. ‘Making a Terrace Garden’. Permaculture News, 22/11/13. http://permaculturenews.org/2013/11/22/making-terrace-garden/ – retrieved 08/06/15
6. La Loma Viva, 2015. ‘About Us’. www.lalomaviva.com/about-us/

To read more of Charlotte’s articles, please see her author profile here.

Related

Popular

5 thoughts on “Understanding Water Part 2: Working with Flow

  1. I recently attended a Joe Salatin talk where they compared the cost of swales and using rotational grazing to improve soil structure and carbon content. The latter technique won hands down (vastly lower cost per acre). I have been using the technique on my property and even with suboptimal weekly cattle movements after only 18 months my pasture quality and diversity is improving. Most interesting is how seeps and springs are already reactivating at the base of my hills. This along with the persistent green of my pastures during droughts compared to the neighbours confirm the improvement in soil structure and water holding capacity is already occurring.

    So personally I think swales have their place (and kudos for showing they can be constructed without depending on machinery) but they mostly appeal to people’s need to feel like they have achieved something, and that it needs enormous effort and expense to be worthwhile.

    1. One meter a minute with a machine, the bigger the swale the bigger the machine so not very expensive for a permanent main frame foundation of a contour forest of course, as swales being a tree growing system and only primarily a water harvesting system, and a nutrient supply to cell rotational grazing as one of the options for inter-swale land uses in a permaculture guild designed landscape.

      A guild is a beneficial assembly of elements often clustered around a central element and it is a permaculture design approach for placement of plants, animals and structures.

      We can design and implement the evolution of a cultivated long term stable system using mixed tree, shrub and vegetable crop, with live stock carefully planned in as foragers.

  2. if you attach a spirit level bubble to the centre stick of your A-frame it as to be a perfect A, if not it will show you a wrong level…

  3. Would like to see info on calculating optimal swale width/depth/spacing for various soil-types/rainfall/slope combinations. That info is far too hard to come by, and much needed – I have seen serious soil-slip problems created when it is done wrong.

Leave a Reply

Your email address will not be published. Required fields are marked *