Permaculture Earthworks

Passive Keyline Inspired Rainwater Harvesting

Design and Installation - 2019

Yeomans, Restoration Agriculture Development and dreams of swimming holes.

Aside from the creek that touches the most remote South East corner of the farm, summer was hot and dry.  Since we moved to the farm we daydreamed about digging a pond for swimming and fishing.  After reading Restoration Agriculture by Mark Shepard we were introduced to the concept of Keyline design, a farm scale water management system developed by Australian P.A. Yeomans in the 1950's.  Entire volumes can and have been written regarding Keyline design, but a few fundamental concepts really shed light on what Keyline design is all about.

  • Water flows downhill.  This one may seem obvious but it has the power to transform a landscape when you are talking about a fall of 6 inches over 100 feet (0.5% grade), water will still flow.
  • During a significant rainfall event first the soil will absorb all the moisture it can until it is fully saturated, after this happens surface runoff occurs (surface runoff will also occur if the rain falls faster than it can be infiltrated into the soil).  It is important to note that for every 1% increase in soil organic matter 26,000 additional gallons of water can be held in the soil per acre!  
  • Once surface runoff begins water finds the quickest path downhill usually concentrating in valleys as intermittent streams.  This is the point where Keyline design aims to intercept the flow of water and divert it into storage ponds instead of allowing it to continue it's downhill flow and leave the farm.
  • At Hooting Hills we decided to accomplish this using a system of swales which are essentially a ditch cut into the side of a hill that follow the contour lines of the landscape but are excavated at a very gentle grade (0.5 - 2%) to divert water into our ponds.

    Initial design goals were to locate the ponds as high in elevation as possible to allow gravity flow irrigation and livestock watering.  The team at Restoration Agriculture Development (RAD) - Eric Berg, Mark Shepard, and Karen Vanek helped us put this vision onto the ground.



    Initial design (not exactly as pictured but pretty close) was done using contour maps obtained from the soil and water conservation and some experience and intuition by Mark Shepard.  Now that we knew what we wanted to do and how to lay it out it was time to start digging.

    We began construction with Eric Berg and a Komatsu beginning of August 2019.  We held a permaculture design workshop the first 3 days of the installation for folks to come out and learn about Keyline design and how to put a system like this on the ground.  It took about 12 days to get everything dug and all the freshly excavated soil seeded with pasture mix.  Owen even got some bulldozer operator training and got to help dig Charlie pond.

    Waiting for Rain

    Currently ponds are still not near full capacity and silting in.

    It seems like every good rainfall we get the ponds fill up to the highest they've ever been.  Then the levels slowly fall again from leaking and evaporation.  We hope this repeated process will draw all the small clay particles and eventually plug and seal the pond (silting in).  Time will tell whether the system will fill up as designed but we are keeping our fingers crossed and enjoying every hard rain we get in the mean time.

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