Using the ground as your rainwater collection tank.

In a previous post, I discussed how rain during a drought can be a bad thing.  The rain doesn’t get to soak in as fast as it falls from the sky, and that makes runoff.  Runoff is water you don’t get to use.  It creates flash floods, and flash floods are fatal.

I referenced Brad Lancaster and his work on Harvesting Rainwater.  He’s not the only source of information, but he is clear and concise, and you don’t have to be an engineer to put the information to use.  (Find out about Brad here)

Brad uses a very old technique to hold water on the property.  It employs berms and swales.  Here is a good example of the technique:

It works pretty simply.  Each depression (swale) runs to a berm.  As water runs downhill, it is collected behind the berm.  This slows the water down and gives it an opportunity to soak into the soil instead of running off the soil.

My front yard used to be approximately 6,500 square feet of hard caliche with scrub grass as turf.  When it rained, it flooded, and the natural slope of the ground ran water across my driveway and downhill on the other side.  In even the smallest of rain, the runoff was so strong it was eating away the downhill side of my asphalt driveway.

I corrected it by installing small berms and swales.  It was easy, here’s hoping I can explain it.

First, I marked off contour lines showing me the slope of the yard.  I made a simple level in the shape of the letter “A”, then attached a $.75 bubble level to the middle, the “-” part of the “A”.  If I put the “A” on a level piece of ground, the bubble should show level.  Here’s a picture:

A Frame

Second, I put one leg of the A on the ground, and move the other leg around until the bubble shows level.  I put a flag in the ground where the legs touch the ground.  I then keep one leg in place and spin the other one until the bubble is level.  I place a flag.  Doing this allows me to draw a line across the yard that is level from one end to the other.

Third, after I have a line drawn from one end to the other, I go back to the beginning, I move 6 feet downhill from the 1st line, then I start a second one.  I repeat these 6 foot spaced lines until the entire yard is measured for level contour lines.  Here’s how the process looked:

Marking contour lines

Alright, the lines are in place.  So what happens now?

Simple.  On the contour line, I trench about half a shovel deep ( I would do nearly a full shovel, but again, it is Texas, I would need a jackhammer to dig that deep.)  I take the soil I removed from the trench and pile it on the downhill side of the trench.  So, I dig the swale and pile the berm.  It is exactly like flippin’ flapjacks.  Trench the shovel in, turn the soil out.  Here’s a visual:

Creating a berm and swale

So how does this work?

It is really simple.  Because contour lines are level across the hill, water will run across them perpendicularly.  ALWAYS.  So, when rain falls, water will start to run off across the swales.  These will fill with the water.  The berm stops the water’s mass and speed from running off downhill too fast and reduces erosion.  Getting the water to stay in place longer means it increases the amount of water that soaks into the soil.

And there doesn’t need to be any more explanation.  Water saved is water I don’t have to spend to keep my plants happy.  Water kept in the soil means building a foundation for soil biology.  Lots of soil biology mean better tilth, meaning better water retention, meaning better foundation….  It also means the more diverse the soil biology, the greater the resistance to disease and pest pressures.

Now, I didn’t want a network of swales and berms across the yard…at least, visible ones.  So, my local community recycling center collects all tree trimmings, storm damage trees, etc, and shreds them.  I’m lucky, they have a pretty fine grind, so it makes a good mulch.  It’s free to city residents, $10 bucks a truckload if not  (for the record, it took 24 pickup truck loads, and my back counted ever single friggin’ one.)  I covered the lawn 8 inches deep in this:

Mulch mulch mulch

This even covering is too deep for grass or weeds to grow through, and, as the rain is saved in the swales and berms, it acts as an evaporation cover, keeping the water there.  So, I’m combining every part of the ground to create a huge sponge.  Here’s some of the finished product:

The finished product

So, I’ve built the foundation of preserving the water that I get from the sky.  All that sweet, free, wet wonder lands on my property; I am keeping ever single drop there for as long as I can.  By doing so, I build the a huge reservoir that hold more water than any tank can (well, and tank of that size that I can afford).  In the process, I build my soil, the second part of the foundation of trying to grow anything.  

Now, as I showed in a previous post, I need to apply this to my back yard.  No more of that wasted water.


About Jeff

A 30-year Central Texas gardener, an instructor of gardening and urban farming in the Continuing Education program with Austin Community College, holder of a Permaculture Design Certificate and operator of Wild Plum Valley Farm, an attempt to turn an urban acre of land into a more self-sufficient homestead without breaking my back or the bank. And Jeff is forever grateful to his beautiful and loving wife Lori. Too many times, the word "I" is used when it couldn't have been done without her.
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3 Responses to Using the ground as your rainwater collection tank.

  1. Ed says:

    I love this information! I wonder if I can use this on my much smaller property (.18 ac). Thanks for sharing and good luck with the backyard.

    • Jeff says:

      Thanks. Yes, it works on any size piece of ground. The deeper the swale, the further apart they can be. I’m really lazy, and I had terrible ground to work with. So, I went lazy, shallow but close. Deep mulch helps, it holds water also. Check out, City of Tuscon, and make sure you look up Brad Lancaster. GREAT info for free. And yes, the effort is worth every penny. Make sure you check out folks planting on the downhill side of the berm. The berm stores water underground, provides a great foundation for the tree.

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