Distances between swales ?

Discussion in 'Designing, building, making and powering your life' started by stevereed, Mar 14, 2008.

  1. stevereed

    stevereed Junior Member

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    Hi:

    I live in Armidale NSW with an annual rainfall in the region of 800mm per year, with a large percentage of that falling in the summer months.

    My block is 4.2 acres with a gentle west facing slope, soil is sandy loan with clayey subsoil , the clay quality is suitable for my dam / pond building activities.

    I'm planning to redirect my driveway on contour with a gentle run off towards the first of a number of swales on contour running across my sloping paddock. Water catchment from the drive and rain tank overflows will fill the first swale and possible a pond just below a spillway, or I may try to intergrate the two having watched the excellent 'Water Harvesting' DVD.

    My question is - what is a suitable distance between swales on a gently (can't be more accurate than that at present) block. Bill Mollison gives a range of figures in the Designers Manual, dependent on rainfall etc, looking at those calculations I could be talking as little as 10-12 m between swales. This is fine, but wonder what others have used and found to be suitable.

    The paddock in question is approx 100m long as it falls down the slope, I'm planning for the swales to run virtually the whole width, with the possibility of a dam at the bottom of the slope as final catchment before leaving the property, the higher pond, with some aquaculture hopes, will alllow for some gravity based usage of the water, including flooding downhill swales as and when required.

    Distancing between swales is my main question, and I'll stick on some pics of the property if anyone's intersted.

    BTW, I have access to a late 1960's bulldozer to do the work and a guy who knows how to use it. Any specific dozer related issues i might encounter???

    Cheers

    Steve
     
  2. Frank

    Frank Junior Member

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    Steve are you able to post a picture or a topographical map of your 4.2 acre farm with contours drawn over it and scribble a few sketches of where you plan to site the dams, swales etc. We might get some interesting comments if you show us what you have and what you plan to do.
     
  3. stevereed

    stevereed Junior Member

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    I've added some basic images of my block and a possible water harvesting plan for debate.

    https://www.facebook.com/album.php?aid=2 ... =598772272

    Having bought the 'Water Harvesting' DVD I really like the idea of multi functional swales.

    The idea is that I will redefine my driveway on contour, and this, along with my household building rain tank overflows will provide a fairly good amount of water to feed my swale / pond system.

    Based on Bill Mollisons Designers Manual I've worked my swale spacings to around 12m apart.

    I look forward to some discussion


    Cheers

    Steve
     
  4. gardenlen

    gardenlen Group for banned users

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    g'day steve,

    i think the rule of thumb is the lower the rainfall the closer together, which may mean as close as 5 or so meters, and in the sandier soils maybe even less.

    on a small parcel of land as yours i would consider a less intrusive swale than the copybook berm type swale, you could use rows of mulch or hay bales which break down over time ammending as they go.

    for us we opted for ripping swale lines mostly very much less intrusive on the landscape and they allow for the water to go more directly to where you need it without the exactness of the berm swale. this gave us the option of repositioning or periodically run the lines again if we needed to. we used some rows of mulch as well all worked to help manage run off water and get int into the sub soil.

    also was the best treatment prior to planting trees we ripped a line then planted into the line as well as along food tree corridors we heavily mulched the row.

    a western slope aspect should make for a good citrus climate or similar type fruits.

    len
     
  5. stevereed

    stevereed Junior Member

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    Thanks for the input Len.

    A few things I have to consider. Firstly the earthworks is free in monetary terms - dozer operator is a friend and we've done a little labour exchange so I'm not having to consider the cost to do the work.

    My paddock is essentially bare, requiring some decent windbreaks to shelter us from bitterly cold SW winds in the winter, the construction of a swale near the house just below a driveway should allow rapid growing of useful windbreak trees and shrubs to offer some protection.

    I have some plans to utilise the 'corridors' between swales for growing some firewood , nuts, temperate fruit trees, AND hopefully a little citrus perhaps close to one of the ponds. Citrus will grow up here but a microclimate needs setting up to minimise the frosting, citrus doesn't appear to enjoy weeks and weeks below -6 at night with a few minus 10's thrown in for good measure.

    Thanks again for the input
     
  6. stevereed

    stevereed Junior Member

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    BTW- The Designers Manual says "given a useful swale base of 1-2 m the interswale space should be 3-18 m. In the former case rainfall would exceed 127 cm, and in the latter it would be 25 cm"

    My rainfall at 80cm (30 inches approx) suggests a swale spacing of 11-12m. I get the impression from the text that high rainfall equals closer spacing - lower rainfall equals greater spacing - -hope I'm right :)

    On the soil issue - mine is a sandy loam on clay - fairly well drained but it holds water for a reasonable length of time - also mulch build up in swales over a period of time should improve water retention.

    cheers

    Steve
     
  7. MonteGoulding

    MonteGoulding Junior Member

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    Hi

    I'm interested in doing some swales on my place too. I've been wondering if spacing should be based on vertical distance rather than horizontal. Or some combination of both.

    Cheers

    Monte
     
  8. gardenlen

    gardenlen Group for banned users

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    as swales go horizontal the distance between is on the horizontal i would think, also i thought the distance or the amount of swales in that case is determined by in low rainfall areas you need more swales closer together, in high rainfall areas you need less swales further apart on a given size piece of land.

    when we did ours in 800-1k mm rainfall area they where about 6 or so meters apart at the widest that is when you are working around slopes and into gully catchments the swales get closer together on the gully catchment areas than what they are out around the bluff of a slope, hope that makes sense? and that was whether the soil was clay or sandy loam we had both. so as we went across a gully not all swale lines continued as we didn't want a plethorer of swales very close together cutting across the catchment, so those lines where broken at that point.

    len
     
  9. MonteGoulding

    MonteGoulding Junior Member

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    Hi Len

    The problem you had in your gullies is what I was thinking about. A vertical distance between swales (ie height difference between contours) would resolve that problem. So if you looked at a cross-section of your land you would see straight lines of swales evenly spaced.

    Cheers

    Monte
     
  10. gardenlen

    gardenlen Group for banned users

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    yes monte,

    even though say only 2/3's or 1/2 the swales continued through the gully at times we had the same amount across all slopes, then as the gully widens and shallows toward the bottom you can fit more of the swales across it. it is all determined by steepnesses etc.,.

    and yes it certainl looked good was low impact on the landscape, took a whole lot less effort and did not need to be so exact across the contours.

    though all the farmer types saw it and complimented the old bloke who used to own the land and he needed to tell them sheepishly that is was the city slickers who bought the place who did the ripping others followed suit it worked a treat.

    len
     
  11. MonteGoulding

    MonteGoulding Junior Member

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    Hi Len

    Did you see that as a problem. Wouldn't you need more (or at least as much) water interception in gullies to halt erosion and spread water along the swales.

    BTW I'm wondering what people think is a better investment. A $1500+GST getting a half metre contour map surveyed or $500 or so on some reasonable surveying gear and do it myself...

    Cheers

    Monte
     
  12. gardenlen

    gardenlen Group for banned users

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    g'day monte,

    nope not a problem just wasn't needed, saved some pollution by less tractor work.

    saved survey money as well as with the rips as it was fairly easy to follow along the horizontal plane, i have a very good eye for level, and rips also can't cause errosion. money better spent elsewhere.

    len
     
  13. stevereed

    stevereed Junior Member

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    My main thought on the distance between swales which would concur with the Designers Manual is that with higher rainfall there would be a need for greater short term 'capacity', hence more swales. A greater interswale area would, after absorbing an initial amount of water, provide a large run off area which may overwhelm the smaller number of widely spaced swales, although spillways would take care of that to prevent destruction of mounded areas.

    Another obvious area to consider is the magnitude and frequency of the rain events, although this is obviously not that easy these days, with large events becoming more frequent and the steady regular rainfall becoming less apparent.

    I am still planning to go for a 'conventional' swale and will plant the interswale area with trees etc on contour too. I do like the idea of using mulch / bales etc and will consider this between my excavated areas as the need arises.

    A particular part of my design plans (although in their infancy) is to use these excavated swales as a means of filling my ponds/dams - preferable IMHO to a diversion channel as the swale will be multi-functional

    Cheers

    Steve
     
  14. bazman

    bazman Junior Member

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    It would also depend if you were going to add live stock to the system, cattle or horses would make a mess of the system in no time at all, so if you were going to fence it off more space might be easier to handle. I'm thinking or adding another swale to the dame over flow but I'm keeping in mind where fences will be placed. Oh and I don't want to be seen "stealing" more horse paddock, heh.
     
  15. stevereed

    stevereed Junior Member

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    I'm really planning to develop a woodlot and a range of edible trees between swales, so the whole area will eventually be providing a product of some sort. We have a feww sheep to eat a bit of the grass down, would probably strip graze then in the inter-swale areas using electric fencing. Some areas may well be fenced - in particular near the uphill pond and the downhill dam, mainly for safety reasons re. kids etc.

    I may well start with 3 swales - one at the top - as an integral part of my pond system (also considering som chinampas close or even adjoined to the pond - -one swale approx midway down the block and a third at the bottom, again integrated with my dam as a multi-functional swale. If I need more I cam alwaysw put them in later - best to have a look at the way they work with the rain events we get and also monitor the moisture levels below the swales.

    Cheers

    Steve
     
  16. bazman

    bazman Junior Member

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    Make sure you have a look over my swale post, it has some costings and the tools I used for the job.

    https://forums.permaculture.org.au/ftopic5973.php

    I have also added some pics on how the area has healed after the land work.

    One thing to keep in mind is make sure your coming into a growing season so the soil does not stay bare, I wouldn't start building one here now as we are going into the slow growing season. My swale is no longer visible apart from a strip of long healthy grass and young pideon pea.
     

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