Swale design

Discussion in 'Designing, building, making and powering your life' started by urbanus, May 24, 2008.

  1. urbanus

    urbanus Junior Member

    Joined:
    Apr 26, 2008
    Messages:
    44
    Likes Received:
    0
    Trophy Points:
    0
    I am currently playing around with water harvesting ideas for a block of land. What is a reasonable rule of thumb for swale separation on a gently sloping block? I was thinking about one for every 2 metres of fall, which would give me roughly 20-30 metres separation between swales and catchment between 1- 2 acres (4000-8000 sqm) for each. I am looking at running the overflow into into hillside dams that each then drain into the lower swale. On a 10 acre block this would give me about 1500 metres of swales with about two acres of trees planted on the ridge above the first swale. Thoughts welcome.
     
  2. gardenlen

    gardenlen Group for banned users

    Joined:
    May 14, 2004
    Messages:
    3,464
    Likes Received:
    0
    Trophy Points:
    0
    Re: Swale design

    g'dau urbanus,

    not sure i can help much? but here are my thoughts:

    first once a trench is sued to direct water to another spot by my knowledge it is no longer a swale.

    now 10 acres not a massive amount of ground and not sure what your plans are ie.,. grazing food animals etc.,. then you need to consider the grazing rate and how much of your land will need to alloted to grazing. my idea was that most of us need app' 5 acres for our infrastructure, gardens and food trees, depending on needs that could be expanded out to 10 acres. then you have habitat management to consider (p/c) and wind breaks etc.,.

    i would however suggest with your swales and wanting to keep as much of the ground fully usable and accessable, why not simply and effectively rip along the contours? these rips can be as permanent or temporary as you like (and they don't need to be as exact as the trench/berm type), and can be redone in a different line to spread the need so to speak. ripping puts the water under the soil where you need it most and aerates. we had a very dry sandy loam to clay block and placed our rips about 6 to 8 meters apart it worked a treat.

    would think that one dam would be sufficient for that sized propery capacity might be 1/2 a megalitr to 1 megalitre?? check your local regulators for catchment waters lots of restrictions on dam building nowadays and also there is likley to be a cost for permission.

    len
     
  3. urbanus

    urbanus Junior Member

    Joined:
    Apr 26, 2008
    Messages:
    44
    Likes Received:
    0
    Trophy Points:
    0
    Re: Swale design

    thanks. I intend to rip the contours for soaking and remineralising if necessary but have been uncertain about width of swales and separation between them as these seem to vary greatly from what I have seen. Unfortunately this area is not well explained on the Water Harvesting DVD or elsewhere on the web or books on this topic.

    I don't plan on grazing the property save a couple of goats for blackberries and scrub with geese, ducks and chickens taking care of the rest. I expect probably close to 3/4 of the block, former cow paddock, will be given over to trees leaving 1/4 for dams, house, garden/orchard and infrastructure. The slope and shape of the block lends itself to smaller dams at each end, with one being about 15m higher than the other, but will think about a single larger one when talk to the contractor. I was thinking of linking the swale overflow to the lower swale by way of a channel similar to a riffle where it does not connect to a the dam. There is also the possibility to capture significant road runoff from a drain but was thinking of putting it into a separate pond to minimise contamination of other water.
     
  4. gardenlen

    gardenlen Group for banned users

    Joined:
    May 14, 2004
    Messages:
    3,464
    Likes Received:
    0
    Trophy Points:
    0
    Re: Swale design

    ther si always trial end error all that anyone can suggest is an idea.

    at least if you don't go the extent of trench swales you can always add an extra rip into the sytem, i always worked on the less rainfall the closer or more the rips. we ahd av' r/f of between 670mm & 1100mm, so found 6 to 8 meters apart worked fery well in the sany loam we had and clay as well.

    yes having channels as well to direct water tha might exit the property before it has gone into a dam is also the way to go.

    grazing rates depends on the type of ground you bought ie.,. scrub country or former riperian bush country, as the aquafa affects the ability of things to grow like grasses scrub country acn have anything from salty enough to grow prawns to just fresh. so talking to local farmer types may help work out your grazing rate if you plan on being sustainable in that sector over stocking will mean lots of ahnd feeding.

    we channeled all road run offs into, our property as well water is what it is all about.

    len
     
  5. urbanus

    urbanus Junior Member

    Joined:
    Apr 26, 2008
    Messages:
    44
    Likes Received:
    0
    Trophy Points:
    0
    Re: Swale design

    thanks again. Rainfall is around 1100mm so your reference gap between contour rips is a useful tip. The property has been cleared to pasture for as long as anyone remembers so the scrub is just the area between fence and road. Soil is rich red clay loam and expected to be suited to intensive horticulture, albeit phosphorus deficient. I guess it will be trial and error with number of swales.
     
  6. Paul Cereghino

    Paul Cereghino Junior Member

    Joined:
    Nov 1, 2006
    Messages:
    89
    Likes Received:
    0
    Trophy Points:
    0
    Re: Swale design

    Hmm... I like the topic... but don't have much concrete experience to offer (never stopped me yet).

    I guess if your already ripping, digging and maintaining swales sounds like work, so I'd say you'd want to achieve the desired effect with as few swales as possible. So then it comes to the goal. If the goal is percolation, I bet it would matter a lot how fast your 1.1m of rain comes? Does the sky rip open and dump (more swales), or does it drizzle forever (ripping is good enough). is the goal to create moist microclimates for select species? then you'd be trying to concentrate good sources of water, and then if you are intercropping between swale/tree/hedge rows, then what spacing do you need to intercrop. Is the swale tree row about wind effects? Are you using swales to deliver water? a different issue. Form follows function... in short I'd inventory the "why" of your swales to figure out the factors that should determine spacing.

    For percolation:
    Distance between swales = (volume of swale * soil permeability)/(steepness * rate of rainfall)

    or.. distance between swales decreases as slope and rainfall rate increases and ability of soil/swale system to absorb water decreases.

    ;)
     
  7. urbanus

    urbanus Junior Member

    Joined:
    Apr 26, 2008
    Messages:
    44
    Likes Received:
    0
    Trophy Points:
    0
    Re: Swale design

    Some good ideas there Paul. Rainfall occurs throughout year with maybe 50% more in winter than summer. I will try and do the math but it gives me an idea of perhaps having one large dam and pumping water into a top swale. I have not commenced work yet so still in the observation and planning stage but clearly less is good.
     
  8. bazman

    bazman Junior Member

    Joined:
    Jul 4, 2005
    Messages:
    802
    Likes Received:
    2
    Trophy Points:
    0
    Re: Swale design

    It comes down to what you want to finally do with the land, If it's a large orchard, you want to leave room to drive a tractor between the swales and give the trees enough growing room and also have places where you can cross them with out damaging them. I tend to think live stock should be kept out of the swale if you can, when things get dry you can use your swales as a quality food source which can be picked at over a fence.

    It also comes down to what you can take on, do it in stages if you like that way you can see the results over time. I have a single long swale right through my block and the catchment quality is amazing, I have also linked it up into my dams wing drains and storm water run off. 25mm of hard rain will fill my swale system and put 25cm of water into my dam. I'm more than happy with that, I do have some ideas of adding another swale which catches the dams overflow.

    If you can go visit a few properties that have swale systems in place, seeing them first hand is the way to go.

    Good luck.

    Baz
     
  9. urbanus

    urbanus Junior Member

    Joined:
    Apr 26, 2008
    Messages:
    44
    Likes Received:
    0
    Trophy Points:
    0
    Re: Swale design

    thanks bazman, I followed your swale construction with interest; btw, links are dead now. How did you determine the width/depth? I like the idea of using the swale as a path. I am not intending to have livestock.
     
  10. foggyforge

    foggyforge Junior Member

    Joined:
    Jun 5, 2008
    Messages:
    115
    Likes Received:
    3
    Trophy Points:
    16
    Re: Swale design

    Hi,gardenlen-im puzzled by your assertion that-most of us need app' 5 acres for our infrastructure, gardens and food trees, depending on needs that could be expanded out to 10 acres. then you have habitat management to consider (p/c) and wind breaks etc.,
    From what i heard Bill M talk on PC he suggest about 10mx10m for food needs of a family .Am i missing something -please elaborate. :?:
    How will the population of the cities survive?Those who never be able to even afford 10 acres?please don't take this as a criticism ,i'm wondering if we talking about PC here?regards ,(foggyforge)Bela :D
     
  11. Pragmatist

    Pragmatist Junior Member

    Joined:
    Jul 28, 2012
    Messages:
    52
    Likes Received:
    0
    Trophy Points:
    0
    That number (10x10m) sounds like about the absolute minimum of planted area for a single person based purely on energy calculations. Working on a 0.3% efficiency of plants turning sunlight into edible energy (typical crop value according to Wikipedia) and 7kWh/day total solar irradiation (on the high end for my area), the total available food energy from 100sq.m is just under 8000kJ/day. Daily energy requirements vary with age/sex/etc. but are typically around that value. Given the amount of physical work required to manage such an area, I'd guess that it would be on the low side for most permaculturists.

    You might be able to increase the efficiency a bit by choosing different plants (sugar cane can be up towards 7-8%) but I'd be inclined to think that a balanced diet would actually require more space as leafy greens have less energy per land area than the starch crops on which the 0.3% is based. Similarly, perennial tree crops would most likely be less efficient with the sunlight as they take space without producing food for much of the year (especially deciduous fruit trees). In the end, you might increase the efficiency a bit but increasing by the factor of 4 required to feed a family on the same area is pushing it a fair bit. Harsh (colder) climates have less insolation so would require even more area.

    That's just the pure food growing area. If you double the growing area (to get a balanced diet without needing to farm the land so intensively) then you get 200sqm of food plant growing area per person or 800sqm for a family of 4. This requirement could still be a lot bigger once you include trees not yet setting fruit (most take a few years to start producing) and some less-efficient plants.

    It doesn't include paths, storage space, buildings, water storage, chook space, compost heaps or any other infrastructure requirements. It also doesn't include the space to grow other crops, such as fuel, fibre, building material and companion plants. It also ignores recreation space. How much space you need for all these other requirements is quite personal but I'd be surprised if most people could do it in less than twice the growing area indicated above (much more if you grow all your own fibres, fuel and building materials). This gives a total site area of about 2400sqm (about 0.6 acre) without producing everything you need on-site.

    Gardenlen's estimate of 5 acres is not so far away from that sort of number, depending on whether he plans to provide for all his family's requirements within the site area.
     
  12. Pragmatist

    Pragmatist Junior Member

    Joined:
    Jul 28, 2012
    Messages:
    52
    Likes Received:
    0
    Trophy Points:
    0
    As for the cities - the short answer is that they probably won't survive in their current form. Our current cities rely on vast amounts of very cheap energy to sustain current population densities and building/lifestyle choices. Unless we (as a population) find something to replace oil in this role, it's likely that cities will devolve into less-dense, more sustainable forms. Personally, I think such cities will be far more pleasant to live in but the transition will be incredibly painful.
     
  13. matto

    matto Junior Member

    Joined:
    Sep 4, 2009
    Messages:
    685
    Likes Received:
    1
    Trophy Points:
    16
    Going by the Designers Manual, swale base should be 1-2m with an interspace of 3-15m. In the former case, rainfall would exceed 127cm qnd in the latter it would be 25cm.

    But going by David Holmgren, swales in a winter dominant rainfall for orchards would be wasteful as the deciduous trees would not be able to take up the water, leading to waterlogging of the soils. Im pretty sure Darren Doherty goes with ripping over swales in the Southern climate of Australia, and most definately supports Keyline dams with lockpipes to utilise water storages in dry summers. The diversion drains in a keyline system still capture water as a swale would, and a one in 400 diversion that is grassed would slow the water down to infiltrate, with a small runoff coefficient.

    Also if you are ripping and mounding tree lines, this is another micro catchment.

    Check the BOM site for monthly averages. Perhaps a few strategic swales to capture summer rainfall could be ideal, and then the line directlyu below the swales are planted with evergreen, winter active trees.
     
  14. Lesley W

    Lesley W Junior Member

    Joined:
    Jul 10, 2012
    Messages:
    62
    Likes Received:
    0
    Trophy Points:
    0
    Urbanus, can you please add a little more detail on the degree of the 'gently sloping' hill? Also what kind of soil are you working with, do you know how deep the soil is before you (may) hit rock?
     
  15. S.O.P

    S.O.P Moderator

    Joined:
    Jul 8, 2011
    Messages:
    1,456
    Likes Received:
    5
    Trophy Points:
    38
    Matto, on the smaller scale where swales for whatever reason aren't necessary or permanent enough, would using something like a Gundaroo Tiller (which Yeoman's refers to as keyline for the home gardener) and punching holes along contour be sufficient as a miniature keyline system?

    Having never studied Keyline, would doing something like that each quarter directly next to the previous quarter's holes be adequate (along with seeding and slashing of cover crops)? Adequate enough to build fertility in and humus on top?
     
  16. matto

    matto Junior Member

    Joined:
    Sep 4, 2009
    Messages:
    685
    Likes Received:
    1
    Trophy Points:
    16
    G'day SOP,

    The good folks at All Sun Farm have been using their Gundaroo tiller for years in a no-till market garden situation. They use a mechanical spader to turn in green manures seasonally and only disc cultivate every few years and have had great successes with building soil fertility.

    You could definately use the Gunny tiller to the same effect as a Keyline plow. Working along contour above trees in an orchard or food forest, with a spacing between furrows of say 30cm would increase water infiltration and allow decomposing green manures to settle into the soil profile. The Gundaroo tiller leaves the soil profile intact as does the Keyline plow and the tines are about 250mm.

    The main difference is that the 22"+ shanks on the Keyline access the subsoil, creating conditions for rapid transformation into deeper, more fertile soils. The idea is to work the soil when it has sufficient warmth and in our climate could be done twice a year. The same would be good practise with the gundaroo tiller, or even 3 times, considering that you are working only in the topsoil. As long as the conditions are right in a warm soil, with decomposing plant matter and chance of rainfall. And I agree, each time you do this, cultivate between the last seasons rows.
     
  17. S.O.P

    S.O.P Moderator

    Joined:
    Jul 8, 2011
    Messages:
    1,456
    Likes Received:
    5
    Trophy Points:
    38
    I've seen used a Stihl petrol-powered drill with Auger attachment for decompaction and aeration of significant trees. The auger, from memory would have been longer than a foot.

    So, in small areas, could you suggest anything else?
     
  18. matto

    matto Junior Member

    Joined:
    Sep 4, 2009
    Messages:
    685
    Likes Received:
    1
    Trophy Points:
    16
    Ive thought a crow bar could do a similar job. Other than that, I think Fukuoka's method of understory planting with tap rooted plants, especially daikon have merit. But the Gunny tiller or even a common garden fork would kick start the process well enough
     

Share This Page

-->