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Drought proofing


 
Drought proofing : Comparing 3 methods of sustainable design     
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Comparing methods of drought proofing (continued)    
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Farm drought proofing: Peter Andrews vs Keyline vs Permaculture There’s plenty of talk about drought lately but is anyone in the media talking about Peter Andrews, Keyline or Permaculture? They should be, because these are all proven approaches to drought proofing farms. Just as well AQOB is onto it! Peter Andrews has been the subject of documentaries on ABC TV Australian Story, author of the book “Back from the Brink” and a controversial figure in Australian farming. One example is the way he rehabilitated a dry gully into a thriving watercourse at a horse breeding farm in the upper Hunter Valley. 

 
1 Dry gully before rehabilitation by Peter Andrews Natural Sequence farming  
And 2. below left: after Natural Sequence Farming
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And 3 below left: leaky weir  rocks slow water down during gentle flow over the flood plain during storm flow Natural Sequence Farming.

 
His methods were (briefly): 1. Vegetate the gully as rapidly as possible. 2. Deliberately obstruct the passage of water down the gully using logs, rocks, branches, living plants – whatever is at hand. 3. Use of a “leaky weir” – a dry rock wall built as a permeable barrier across the gully.  After a minor storm, rain that would otherwise rush through the gully in a matter of hours or days is forced to back up and move more slowly down the streamway.

 

Larger storm flows are directed away from the stream over to the ridges, which soak up water and slowly redirect it back to the gully. Peter Andrews was controversial because he deliberately used weeds to achieve rapid revegetation. Also, it was alleged that the practice of obstructing and diverting water would deny farmers downstream of water. The most controversial aspect of his work is that it worked – regular streamflow was achieved and farmers downstream benefited as a result.

 
“Keyline” was developed in the 1950s on a North Richmond property (Yeobarnie) by P.A.Yeomans. Keyline is a network of co ordinated drainage lines and small farm dams. The “key point” is that point in the humid landscape (i.e. a region where annual rainfall exceeds evaporation) where slope changes from convex to concave. It is usually the highest point that dams can be economically built. Under keyline, the entire width of the property is excavated with a shallow drain following the contour line ( a line made of points of equal height above sea level) at the key point.

 
The drain feeds water into one dam, which overflows into the next, and so on. Another series of drains and dams follow at lower elevation, and another lower still, and so on. The advantage of keyline is that all runoff down the property is directed into surface storage (dams) for use during dry times. This storage is located relatively high up the slopes, allowing gravity fed irrigation over a wide section of the property.
Yobarnie the original model farm for keyline established by P A Yeaomans.

 
Permaculture is a multidisciplinary sustainable design approach. Human needs (housing, food, materials, water, energy, society, etc.) are arranged as a deliberate ecology with mutually beneficial connections. It is not defined by any particular technique, however swales and a modified keyline using swales are frequently used by permaculture designers.
Tagari Farm Permaculature Institute uses keyline a network of small dams and swales
into soil

 
A swale is a trench and mound excavation. The floor of the trench is perfectly level, so too is the top of the mound wall. Under light rain, water sits on the swale floor at equal depth along the entire length of the swale (which may be hundreds of metres) and slowly soaks into the landscape.  In semi arid areas, storing water in surface dams leads to salt accumulation and is not viable. However swales are practical as water is fairly quickly soaked into the soil.

 

Trees are planted on the downhill swale mound to further assist in shading and absorbing water into the soil. Under heavy rain the swales fill and can be arranged to overflow at each end into a keyline sequence of dams.

7. Zaytuna Farm The curved landscape result of trees planted on swales following the land contour lines Google Maps.jpg


 
The take home message is that a range of techniques exist to avoid or minimise the heartache of drought. They generally involve slowing water down, soaking it into soil, careful and sensitive excavation and understanding that our greatest allies are trees.

8 A excavated dam and connecting swale filled from a higher dam the day of construction to check for leaks and level.

 
Zaytuna Farm: an established swale after heavy rain.

Swales may take a few days to soak into the soil.

For more information, please contact us
 
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